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Do I need to go to a top college to be successful in computer science? | I'm currently a freshman in college majoring in computer science. The college I am going to is a smaller, local college that definitely is not prestigious or world renown. I was wondering how much influence the college I went to will have on my future attempts at getting a job. I have a passion for tech and coding and learning and I want to do very well in this field. Also, I just landed my first internship which is exciting. But, will my degree from this little college cause me any trouble later? Or am I just overthinking this? | There might be a starting height cap and a starting wage cap difference but ultimately you will not want for jobs if you are doing software engineering at all, many companies hire on the spot for passing a basic programming test and will put you in at some pretty great wages.
Note a Bachelor's degree opens a whole lot more doors than an Associates Degree. You will see your starting wages pretty much double in some regions for the difference. | 21 | 16 |
ELI5: why didn’t humanity advance technologically for thousands of years when it comes to things like electricity and other electrical power devices like WIFI, but now humanity is advancing rather rapidly? | The ability to produce excess stuff allowed more human resources to be focused on new technology and methods. This further increases productivity (since we started at a low level) and this frees up even more human resources to do new stuff.
Prior to the industrialization, most (say around 80-90%) of the world's population had to work in agriculture (or very nearby occupations - transportation, etc) simply to feed societies. This kind of economic system is very sensitive to weather etc and things like hunger, disease and famine were not uncommon. Basically the vast majority of human effort went to provide the basics like food and shelter - education, science etc were restricted to a small elite.
The industrial revolution meant that transportation became much easier, things like cloth became easier to produce, labor moved from farms to cities. Cities are a great form of organization for human interaction and innovation. | 130 | 43 |
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How do I productively discuss the "realness" of human constructs like money, finance, law etc | In particular, I find that people like to say "the stock market isn't real", and in an abstract way, they are right, but there is so much more to it. Love, marriage, law, political borders, money, finance - are there better terms, phrases or concepts that address the impact of topics like this I can use to come to an understanding with people with no philosophical background? Whether it's "real" seems so far beside the point one might want to make with such things. They have an impact, and how we choose to relate to them is so much more complicated than what I have been able to get at. "Illegitimate" seems to be what most people more closely mean when they say those things aren't real, but it's a hair that's too difficult to split without the right language set. | The term is socially constructed. Social constructs are very real, and any social constructivist will tell you as much. Just because something isn’t a part of the natural furnishing of the world it doesn’t mean it’s not real. | 28 | 73 |
Why are some viruses only transmitted by blood/sex and some only by saliva | Reading about HIV I got wondering *why* it's not transmitted by spit? What's special about blood and sex fluids that saliva lacks?
And then I realised that the cold & flu are transmitted by coughing/sneezing (presumably saliva) and I've never heard anyone get the flu from sex.
Why do some viruses get transferred by some methods while others get transferred by others? | Viruses rely on receptors on the outside of cells to recognize cells (and gain entry into them). Different cells have different receptors, and so different viruses recognize different types of cells.
The same way that a lock pick will not get you into a door with a digital keypad, and a circuit analyzer will not get you into a door with a regular key lock. | 11 | 52 |
ELI5: What is the common cold? | I had an idea that it was just an extremely common virus that we can't cure. However, upon looking it up some sources say that there are over 200+ viruses that cause the common cold. Does that mean the common cold is just some blanket term we have for viruses that cause these symptoms? | The common cold is a syndrome (a constellation of symptoms) which can be caused by several different viruses. It's difficult to count the number of viruses because of how many strains, variants and subvariants exist if each. But it's thought that the most colds are caused by rhinoviruses, while many of the others are caused by non-SARSCoV2 coronaviruses.
It can also be caused by respiratory syncitial virus, adenovirus, coxsackievirus, parainfluenza virus, influenza and of course SARSCoV2 (covid-19), but there are several other potential viruses than can cause similar symptoms. Many of these virus also can cause more several disease, whereby most people wouldn't call it a cold any more. These are more appropriately called flu like illnesses, which unfortunately some get mixed up with the stomach flu, which usually has nothing to do with influenza at all. | 27 | 30 |
Pros and Cons of Auditing the Fed. | I'd like to hear thoughts on the recent bill from some economists. | It's a tough issue because it's at the intersection of 2 important, popular beliefs and some question whether they can coexist in this case. Those 2 beliefs are:
1. That transparency is generally a good thing.
2. That the Fed should remain immune to short term political pressures.
While some people maintain that the Fed can be transparent and still remain immune to political pressures, many people question why you would audit an institution if you have no desire to influence it in any way. What if the audit turns up something that is politically unpopular and a politician decides to exploit it for political gain? Another argument is that transparency is inherently a form of influence.
| 13 | 22 |
ELI5: How on earth is the "Chance of Rain" calculated? | Meteorologists collect lots of information about weather. They measure wind speed, cloud clover, how much it rains, the barometric pressure, etc. With all this information, they notice patterns and can use those patterns to predict the weather to some extent.
For example, if in the past, it rained 40% of the time when the clouds formed like they are today, and other weather factors were also similar, they would say there is a 40% chance of rain. | 19 | 22 |
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What is the purpose of eyebrows? | I was pondering this question earlier today while thinking about extremist groups that shave their eyebrows. What is the anatomical function of eyebrows? | Eyebrows are hypothesized to have two main functions: to prevent debris, such as dirt, sweat, or dust, from falling into the eyes from above (in addition to the protection offered by eyelashes) and to offer an additional means of facial expression. | 15 | 15 |
ELI5:What is the purpose of Nautical Miles and why dont we just use regular Miles or Kilometers for ocean or air travel? | Nautical miles are useful because 1 nautical mile is 1 minute of latitude, or 1/60th of a degree of latitude. It makes them useful when navigating on charts, where latitude and longitude are in degrees and fractions of degrees. | 171 | 117 |
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[Star Wars] What exactly did they take from Jango Fett to make his clones? | Was it blood? A Hair Sample? Cheek swab? How much did they need? Did he have to come back to donate more later on? | It's not specified, but it's likely blood, tissue samples and bone marrow. He did in fact had to regularly return to supply additional samples, which was plot point in Clone Wars - since there was no more any Jango Fett, kaminoan cloners faced an issue that their supply is limited. | 48 | 17 |
ELI5 why credit inquries lower one's credit score | If one is simply looking up her or his credit score and is not making a purchase on credit, why does his or her credit score take a hit? | You may check your own credit rating as often as you'd like with no impact to your overall rating.
Creditors (without your knowledge, i.e., those credit card offers you get in the mail) may check your credit rating as often as they'd like without impacting your overall rating.
Creditors (acting on your behalf, as in you applied for some sort of credit) checking your credit rating **will** impact your overall rating.
The third situation has the potential of impacting your overall credit rating because this type of query is only done when you apply for credit. The presumption is that if you have applied for additional credit, you are planning on borrowing for something. The impact of the query is nominal and short lived if you don't borrow the money. If you do borrow, then your score would be recalculated based on the other factors (overall credit vs debt, credit history, etc.). | 301 | 674 |
Does Occam's Razor eliminate teleological explanations for phenomena? | Here's an example:
Why does a bacterium swim up a glucose gradient to a food source?
The reductionist way to answer this would be to examine the glucose receptors, and what protein messengers they trigger, which result in deformations in the outer membrane.
The teleological answer would say that the bacterium goes through that chemical process *in order to* reach the food source.
While a combination of both explanations are needed for complete understanding, it seems like people tend to consider the reductionist answer to be more real, probably because purpose isn't measurable.
Is an immeasurable but seemingly real phenomenon considered an assumption to be eliminated by Occam's Razor?
EDIT: A better example of teleology being a more effective agent of understanding is explaining why salmon swim upstream. Reductionism examines the chemistry of the fish, where teleology finds the purpose, that is to lay its eggs. | One important thing to remember is that Occam's Razor is a guideline for theories that have equal explanatory power. It is open to a teleologist to insist that his or her account has more explanatory power, and that, for this reason, its greater complexity does not count against it.
Another thing is that the example you gave is a tricky one. Why should we say the bacterium goes through that chemical process 'in order to' reach the food source? That sounds like a intentionalistic projection onto a creature that is not capable of having intentional, goal-directed action. Why would we need that sort of explanation 'for complete understanding?' Nevertheless, in explaining human or other animal behavior, teleological explanations are very helpful. | 17 | 15 |
What is the societal purpose of dignity? | Assuming dignity is a social construct (another question would be if this is a valid assumption to make), it must be serving some purpose to the society. Has this been explored in any way by social science and if so, where could one look for relevant studies? Thanks! | Honor and reputation was more important in the past when costs of monitoring were greater. Thus, organizations and institutions developed to fill this lack of information. For example, the idea of a duel was to signal an investment in reputation (willing to risk the fire consequences). Interestingly, dueling pistols were intentionally inaccurate in order to mitigate the cost.
A source for this is The Institutional Revolution by Doug Allen | 12 | 21 |
[Super powers] What if you had the ability to manipulate the Higgs field, would this be a useful super power? God-like? Completely Useless? | You would be able to change the mass of objects at will. Particles passing through the higgs field is part of gives matter mass. If you could change the localized density of the field, you could make things heavier if you made the field denser, and lighter if you did the opposite. You could in theory make localized black holes and dissipate them at will. | 14 | 29 |
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ELI5:What happened to unbleached paper products? | Back in the 90's environmentally conscious consumers learned to shop for unbleached paper products to reduce the amount of toxic materials required for production. It meant the product were invariably very off-white but still fully functional. Seems like these products have totally disappeared from retailer shelves. What happened? | Basically they found far more environmentally friendly ways of achieving the same effect without bleach. Mostly this will be hydrogen peroxide. This is H2O2 - water with an extra oxygen molecule. It breaks down into water and doesn't pollute and is cheap and easy to produce. Things that used to be 'unbleached' are more likely to be advertised now as 'chlorine free'. Chlorine was the main bad thing about bleach. | 48 | 122 |
eli5: how did Hellen Keller understand what words meant | I know I sound dumb but I’ve been thinking about this and I just need answers please help | A very patient caretaker/instructor. There are movies/books about this for more detail if you want more than base level. But Hellen would feel the instructor's throat. Each sound we make feels different. Just like learning any language, Hellen was able to then feel her own throat and find out how to make the same sound to mimic it. They would also associate those sounds with objects or actions. The mechanics of the learning process were different in that she had several difficulties to overcome, but the process was similar to how anyone else learns a language. | 189 | 131 |
CMV: Hospitals delivering babies should have a policy of assumed paternity testing unless both parents express that the opt-out. | There are many things hospitals do during or shortly after delivery as a matter of policy. Many new parents don't even realize they are being done, or didn't realize they would be done until the delivery. This includes a hearing test, blood typing, and testing for around [31 different disorders](https://www.babycenter.com/0_newborn-screening-tests-which-ones-your-baby-will-have-and-w_1471069.bc). I'm suggesting we include in the battery of newborn tests, a paternity test. This would be something that is done as a matter of policy, and can only be opted out if both parents agree to opting out (perhaps by signing a waiver). Benefits of this policy would include:
* Reduced occurrence of people finding out there dad is not their bio dad later in life (and associated traumatic experience).
* Reduced occurrence of men finding out they have a child they were never informed about.
* Reduced occurrence of fathers finding they have been cheated on/lied to regarding their parentage only after years of providing physical/emotional/financial support.
Presumed objections and preemptive counters:
* This will add unnecessary cost to the delivery process. -- Google says paternity tests cost from $50-$500, and that the total cost of delivering a baby is around $8,800 on average. As such the cost of the paternity test seems negligible. One could also make the same argument about the battery of tests already being done.
* We can't force women to take a test they don't want to. -- Correct, but we aren't testing the women, we're testing the babies. This would be after the delivery.
edit: *they (in the title)
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> *This is a footnote from the CMV moderators. We'd like to remind you of a couple of things. Firstly, please* ***[read through our rules](http://www.reddit.com/r/changemyview/wiki/rules)***. *If you see a comment that has broken one, it is more effective to report it than downvote it. Speaking of which,* ***[downvotes don't change views](http://www.reddit.com/r/changemyview/wiki/guidelines#wiki_upvoting.2Fdownvoting)****! Any questions or concerns? Feel free to* ***[message us](http://www.reddit.com/message/compose?to=/r/changemyview)***. *Happy CMVing!* | How are the samples from the father being obtained? You would surely need to ask the alleged father's permission to take samples from him, so it essentially amounts to offering the father a paternity test, which doesn't seem that different than the current system. | 22 | 24 |
ELI5: What is the purpose of "Not to be removed except by consumer" tags on mattresses, pillows, and the like? | There are laws requiring certain items (for example, upholstery, mattresses) to be labeled clearly showing what they are made of. It's illegal for the store or the wholesaler to remove the tag before the final consumer buys the item, because they are entitled to know what it's made of. | 74 | 129 |
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Disregarding the fact that people are considered mature or an adult at age 18(in most countries). At what age do different philosophers consider a person an adult? | I'm guessing that people have different ideas of what's the ideal adult age. I think that I could consider myself an adult at age 25 and beyond. I could call myself an adult at age 18 anytime but I wouldn't feel like one. | What we mean when we say that someone is mature is that they have developed a certain set of capacities. These capacities can be a number of things, including things like the capacity to drive a car well. But the most important type of capacity we tend to associate with maturity is rational capacities. The reason that we don’t punish children as much when they commit the same crime as adults, or that we don’t let them vote, is that we feel they don’t have sufficient rational capacities to fully understand what they are doing. Rational capacities seem especially important for assigning moral responsibilities to people. The problem is that there is no clean line we can draw where before the line someone lacks rational capacities and past the line they have them. Further, it’s possible that there exists some very mature 15 year old who has developed sufficient rational capacities, and that there is also a very immature 25 year old who does not have these capacities.
The law draws a line at a certain age because of pragmatic considerations. It is simply impossible to go case-by-case and decide whether each person is currently rational enough to take on the full moral responsibilities of an adult. So we draw a somewhat arbitrary line that we decide is good enough, but not perfect. Philosophers don’t have to draw such a line, so there’s no age that a philosopher is going to tell you that someone is an adult outside outside of the political community they’re in. | 11 | 17 |
ELI5: Ninth Amendment | Canadian here. What is the meaning of the Ninth Amendment, and what are examples of laws that would violate the Ninth Amendment. | It basically allows for the possibility that the founding fathers didn't account for 100% of the rights a person has and will always have and allows for "common sense" interpretations of those rights so that they don't need to be explicitly stated in the bill of rights for them to exist and be real.
It's basically meant to ensure the government doesn't try to restrict peoples rights to the limit of a literal interpretation of the bill of rights. So even if a law was crafted that was meant to restrict all free speech except what is explicitly stated in the first amendment, the law would fail because the 9th amendment says there may be more rights that are covered but not writen in the bill of rights.
This helps keep the door open for future amendments that are meant to specify rights that weren't writen down previously. | 26 | 20 |
[Terminator] Why doesn't skynet use chemical and or biological warfare against humans? | I haven't watched the Terminator:Genesis , if they do use that against them then I'll have to watch it. If they didn't use it then why don't they? Why don't they engineer a superbug that resist all medications and kill all humans. Why kill them with machine guns and laser guns when you can just sprinkle them with virus and whatnot? | Those methods work less effectively when the population is scattered and scarce. You need humans moving between places to effectively transmit a disease between populations and the remaining humans may not be traveling between clusters enough to make it worth while. Any survivors would have immunity as well. It’d be much easier to just contaminate/destroy water sources or use radiation than biological agents. | 39 | 40 |
How does Hegel's use of the term "phenomenology" differ from its usage in 20th century phenomenology? | I'm new to the history of philosophy. I know a bit about Hegel and the phenomenological tradition that proceeds Husserl, like Heidegger, Sartre, etc. I can tell that, for instance, Husserl and Hegel mean different things when they consider phenomenology, but I don't know enough to really understand what the fundamental differences are. |
One of the most salient differences is that Hegel conceives his phenomenology as a progressive process that involves different stages whereas 20th century phenomenology is a method of describing a phenomenon. One is diachronic, the other is synchronic. The two also have different aims so they mostly just share the fact that their main concern is phenomena. Hegel calls what he does a "phenomenology" because it is concerned with a progressive set of experiences of consciousness (the way the world appeared to us in different configurations of rationality). Husserl named what he did a "phenomenology" because he wanted to develop a science that'd explain the structures that rule the way things appear to us. | 50 | 122 |
ELI5: How do chip design engineers make sure that there is no interference between different circuit modules due to electromagnetic fields, given that every circuit component is very close to each other? | Specialized design, simulation, modeling, testing, and careful material design. They make sure that the traces are the right shape and length so as to not act like antennas, using ground layers and traces to shield, and more design requirements. Things like the encapsulation materials are specially designed to restrict the propagation of fields. | 219 | 636 |
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I want a PhD in humanities. But I'm not a strong candidate and in my last year of undergrad. What can I do? | I recently had tough extenuating circumstances. I have poor GPA from a completely different major (STEM) that I started out with. I am essentially rushing to finish my new major this year. I do however work closely with my professors, will have research, good grades on my major classes.
Conventional wisdom is to get a masters and then apply, yet there's no way I can afford to pay 50k/year for a masters program. How would I improve my chances?
(the field I want to study is film studies/cultural studies) | Would you work at a CC in rural Arkansas to pursue this dream? Would you be willing to move every year or so as an adjunct, being paid less than your college graduate friends without PHDs? Unless you passionately want to do the career, I'd think hard. And not just because you will have trouble getting into a leading program. | 49 | 28 |
CMV: Sports students should not get special treatment or exemptions. | One student's extracurricular hobby shouldn't come with special allowances, exemptions, and treatment unless other students also receive the same allowances, exemptions, and treatment.
This bothered me as a student, and infuriates me as faculty.
It's simply not fair that random athlete #2254 gets to skip a class for their hobby while another student would otherwise get a grade reduction for such an absence.
It's also not fair that student athletes should get priority grading. As faculty I recently got a request from the administration to submit grades to athletes first. Fuck. that.
What reason should student athletes receive special treatment? What is the rationale that sets them apart from any other hobby or extracurricular? | Would you hold music students to the same standard?
In high school we'd have about 5 days off school to travel to and from national marching band finals or an out of state competition. In the winter, percussion ensemble would do the same for about 5 days, and the concert band would take anywhere from 5-10 day tour somewhere as well in the spring. Occasionally to support these trips we'd hold some extra rehearsals during the school day, which we were also exempted from class for. Teachers were always very lenient with assignment due dates and makeup work. College was very similar in terms of schedule and leniency with professors. | 14 | 34 |
I have a professor who thinks political philosophers and moral philosophers are necessarily not analytic philosophers. Is this an idea people generally entertain or is she just insane? | I argued about this with her at the end of class for about ten minutes. I brought up that political philosophers like Nozick and Rawls as well as moral philosophers like Singer identify as analytics and are in analytic departments but she didn't accept my answer, claiming that moral/political philosophy is just not analytic and no conceptual analysis goes on there, going as far as to say it's no longer an accepted method of doing ethics. Can someone please make sense of this for me or at least back me up in my judgment of her statements? | Some people use the term "analytic philosophy" to refer to a short historical movement headed by Russell and Moore (amongst others). If that's what she has in mind it half makes sense, provided you're willing to ignore Moore's *Principia Ethica*.
There's gotta be something that she has in mind. | 14 | 17 |
ELI5: How do some people with Dissociative Identity Disorder exhibit abilities while in some personas that there real self can't do? | I was reading about the case of Billy Milligan, who had Dissociative Identity Disorder and had 24 documented personalities: https://en.wikipedia.org/wiki/Billy_Milligan#Personalities
One of these personalities could write and speak in Serbian and was extraordinarily strong. The page doesn't say that Billy, in his normal persona, could speak in Serbian. How is this possible? And how could one of his personas be far stronger than another? | As for how, the general consensus is that he learned at least some of the language somewhere, and that it took off from there. There are multiple cases dealing with brain injuries that deal with complete changes in personality and sometimes complete changes in language, so an alter ( alternative personality) knowing a different language isn't completely impossible. How Regan knew Serbian while Billy didn't? It's the same as why you might know English better than someone else. Regan is technically a completely different person. So he may think and speak in Serbian as his first language and English had secondary. You have to understand that the question isn't really why Billy can speak Serbian, it's where did Regan learn Serbian from. It wouldn't have to be a lot, just enough for Billy's brain to learn more.
Example: You know the French word for dog and door. You see a dog walk through a doorway. Someone says in French "the dog walked through the door", you can figure out which word means "walked". Now you know the French word for "walked".
The brain is capable of amazing things. Absorbing a language isn't that hard for a brain wired to do so. That's why there are some people who can learn and speak in multiple languages easily, while someone else under the same circumstances, with the same opportunities, may not be able to learn a second language to save their life. Once the Regan personality fully developed he probably just went and interacted with Serbian people and media, which expanded his vocabulary.
As to how he can be stronger while still only possessing the qualities of Billy's body, that deals with Regan's mindset.
Have you ever seen people psych themselves up before lifting a heavy weight? Or someone else is yelling at them to "get mad at it"? People tend to exert more force when they're angry, even if you discount adrenaline as a factor. People tend to be stronger than they know, but without proper motivation or the proper mind set, they don't exert their full capability.
With Regan being the angriest personality (he was referred to as the "keeper of hate") he would be more likely to put more effort behind something than Billy would. Therefore he'd be utilizing more of their body's capability (basically putting more "umph" into it) than Billy would.
In other cases, it comes down to the simple fact that the brain is the epicenter of DPD, and the brain tells everything else what to do. It could simply be that Billy's brain is convincing his personality that he's weak. He goes to pick up something, and he can't because his brain tells his muscles that they can't handle the weight, while it tells Regan's personality that they can.
When dealing with the traits of different personalities, outside of obvious answers, you start getting into unsolved neuroscience. Unlocking the brains full potential. If someone could figure out and reproduce how Regan learned Serbian without Billy really trying, they could make a whole lot of money selling that ability to people. There are cases of a personality having a disease that the others didn't. Why? Because no matter what condition your liver/kidneys/lungs/whatever are in, if your brain convinces them that they're not working, then they'll stop working.
EDIT: more information | 43 | 116 |
ELI5: how is it possible people can create things like working internet and computers in unmodded Minecraft? Also, since they can make computers, is there any limit to what they can create in Minecraft? | Minecraft provides the fundamental elements required to build a computer: circuits (wires), logic gates, memory and a clock, as well as mechanisms for input (programming) and output. With these basic building blocks you can theoretically simulate a functioning computer, though there are practical limits to how easy it is to build it and how fast it can process instructions. | 5,389 | 10,792 |
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ELi5: How does smoking cause cancer? | Chemicals in tobacco cause damage to the DNA in cells in the body. These cells then divide into other cells with a higher number of mutations then they would have without the damage. The higher the number of mutations the greater the risk that one of those mutations will cause the cell to become cancerous.
Every time your cells divide your basically playing a cancer lottery with relatively low odds. Certain environmental factors increase those odds, tobacco smoke is one of them. | 12 | 27 |
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ELI5:Why isn't the remote finder feature common on TVs? | When you turn on the TV manually, a sound comes from the remote until you press a button. Why isn't this feature on all smart tvs? | Most TVs use IR (infrared), which require line of sight to the TV - (the remote sends a series of invisible 'blinks', like morse code).
The TV doesn't have a way to send a blink out, and even if it could, the remote is probably lodged inside a couch saying "screw you hippy i'm taking a nap, come and find me, suckah".
If the TV used RF (radio frequency) then it could do that, but then the remote would have to listen for that RF signal, which would eat up the batteries.
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Can erbium be used to stop a nuclear reaction? | I saw on periodicvideos that erbium is a nuclear poison. It was described as killing any nuclear fission dead. If that is true, at what scale can it do this. Is it possible to produce a sort of safety kill switch for nuclear reactors? Or is the amount of erbium required just too massive? Or is there a reaction that makes this unfeasible? I had never heard of a nuclear poison before. | The particular situations you're referring to (fission reactors or weapons) rely on chain reactions involving neutron-induced fission. Neutron-induced fission reactions often release more neutrons, which can further cause more fission, and so on.
If you are able to remove neutrons from the system, for example by absorption, you can "poison" the chain reaction and stop it from continuing.
Certain materials have very high probabilities to capture neutrons, and once those neutrons have been captured, they no longer contribute to the fission chain reaction. | 11 | 16 |
The physics behind breaking boards in karate | I was just curious and decided to work up a simple physical model of breaking boards, so I was hoping you guys could verify this idea:
**Motivation:** As with many other martial artists, I've broken my share of boards in my day. I've found that if you hit a board and it doesn't break, it hurts like an SOB. But if you do break it, it doesn't hurt at all. You'd think hitting the board harder would hurt more (Newton's 3rd Law).
**Model:** We have a fist flying at the board with initial velocity v0. I modeled the board as a simple spring, F = k x. If the board is stretched past a certain point, x=x_b, it will break and exert no more force on the fist.
**Analysis:** *For the analysis, I dropped the spring constant, the mass, and various factors of 1/2. They aren't really relevant to the analysis, and they'd sort of muddle the point a bit. So I'll be using kinetic energy E=v^2 , potential energy U=x^2 , and momentum p=v.* The initial energy of the fist goes as E_0 = v_0^2 , the initial momentum goes as p_0 = v_0. Once the board reaches x_b, it has absorbed the most energy it can absorb, U_b = x_b^2 (The corresponding momentum is p_b=x_b). If anymore energy is introduced it will snap; any less energy and it will return to its starting position. The final energy of the fist then will be either E_f= 0 or E_f = E_0-U_b=v_0^2 - x_b^2 . The final velocity then comes from: v_f^2 =v_0^2 -x_b^2 . That makes our final momentum v_f=√(v_0^2 - x_b^2 )
**Conclusions:** The energy taken away from the fist will always be U_b or less. If E_0>U_b, the energy loss will always be U_b. The momentum loss will be dp=v_0-v_f=v0-√(v_0^2 -x_b^2 ). The energy/momentum statistics of breaking a board will be the same if you just barely manage to break it vs if you just barely don't break it, ie. you've still lost U_b energy and p_b momentum over the same amount of time. Since x_b is constant, as v_0 gets higher and higher, dp actually decreases. That means the impulse from the board actually diminishes with harder punches. This is the reason breaking the board doesn't hurt.
**Summary (TL;DR):** The reason breaking a board doesn't hurt, while not breaking it does, is that you break the board so quickly the board cannot deliver an impulse to your hand. The amount of force the board resists with will always be the same, no matter how hard you hit it, but breaking through the board quickly makes it so the force can't do much damage. Consequently, if you just barely manage to break the board, it will hurt almost as much as if you didn't break it, but hitting it even a little harder will drop the impulse considerably. | The conclusion is qualitatively correct, but you should analyze collisions from a momentum point of view instead of an energy point of view. The reason is that energy needs to take into account the sound, heat, deformation, etc. that are generated from the collision. Momentum is just straight up conserved.
Your fist has momentum p0, if it breaks the board, it has a lower momentum p1, but not by much. If it doesn't break the board, your fist essentially stops, and the board has to provide all of the momentum change, -p0, which hurts like a sonovabitch. | 10 | 21 |
Published philosophy papers less than ten pages that most first year college students would be able to pick up and read? | After years of despairing at the quality of papers in my intro course, I'm realizing that we don't read a whole lot of good models of philosophical reasoning. So I was thinking of basing a course around short, self-contained, well-reasoned papers that a) make explicit distinctions, b) consider counter-arguments, c) require little to no prior training in philosophy and d) don't treat the reader as if he or she should be familiar with the broader debates -- such as referring to philosophers we may not have studied. Any ideas for such papers?
So far, I've come up with:
- Singer's "Affluence, Famine and Morality"
- Bennett's "The Conscience of Huckleberry Finn"
- Nagel's "The Absurd"
I wish I could think of other examples in philosophy of mind, political philosophy, the free will debate, and metaphysics or epistemology in general. | Gettier's "Is Justified True Belief Knowledge? ". It's incredibly short and concise given the kefufle it raised.
Edit: Nagel's "What is it Like to be a Bat?"
Historical Answer: Descartes's Meditations | 16 | 48 |
ELI5: Why only humans need to cook food to eat it? | Cooking food can be thought of as the first stage of our digestive system. Cooking breaks down the food, and allows our digestive tract to more effectively use the energy and nutrients...
In fact it's thought that the discovery of cooking (and resulting huge leap in energy intake for relatively little output) was the main driver for the development of our brain..
We can survive on a mainly raw diet, but cooking food allowed us to take the next evolutionary step! | 56 | 90 |
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ELI5: Why does the game of Chess seem so prone to having incredibly young prodigies who can beat masters who have been playing for decades? | It seems like there have been numerous individuals who were recognized as savants at Chess at a young age, and were able to take down some of the greatest players in the world. What about Chess makes it possible where a young child could naturally see the best move possible, when going against the world's best? | They study the technique of the master that they're going to be competing against, and learn how to counter that one guys strategies. The chess master, on the other hand, has no idea who this kid is and so they will not be prepared for whatever moves they decide to make.
Also, strategy designed specifically to beat a single opponent was how the first computer won against that chess master. | 582 | 667 |
If our tears are salty, why does salt water sting our eyes? | I've always been curious as to why my eyes burn underwater in the ocean but my tears always taste salty. | Great question! Let's consider any differences in those two types of saltwater. Now aside from microorganisms and other nutrients and minerals present in seawater the main difference is that the oceans are saltier than our tears. That is not to say our tears are not salty- medical fluids such as IV drips or contact solution have a small amount of salt in them to match the fact that our bodies have small amounts of salts dissolved (Na, K, Ca, Cl mostly). Pure water would be bad to put into a person actually, and small amounts of salts prevent over or dehydration. tl;dr In short, more salts in seawater than tears- so it stings. Tears don't sting because they have as much salt as your body already is working with in them. | 64 | 99 |
ELI5: Vehicle mpg as it relates to speed | An argument broke out at work today . A co-worker pondered if you have to go 100 miles why not go 100 mph as opposed to going 50mph . He figured you'd get there twice as fast and since the engine is running half the time you'd use the same amount of fuel. He surmised that because of the gearing in a transmission you'd still be at say, 2000rpm's in 5th gear, using the same amount of fuel but less time on the road. I failed to explain why I think he's wrong ....please eli5 | RPMs of the engine are taken into account, as well as air resistance. Air resistance doesn't increase evenly. Going 100mph is much more than twice as hard as going 50mph, from an energy standpoint.
Gently going 50mph in your highest (most efficient) gear for 100 miles will save you a LOT of fuel over going 100 miles at 100mph.
In many cars released in the past five years, you can track your gas mileage and find your average MPG, so it would be fairly simple to test it.
Or even get on a bicycle. Ride 10 miles. One of you ride it at a leisurely pace, and the other go as fast as you can. Which of you is more tired at the end? | 92 | 161 |
CMV: I like the idea of Universal Basic Income, but I do not believe that it would be sustainable. | A friend of mine recently showed me [BasicIncome](https://www.reddit.com/r/basicincome), and I find it intriguing. The benefits look great if a UBI system could replace Welfare and Medicare/Medicaid/Obamacare, but I do not believe that this system could ever exist because the US Federal Budget is not large enough. On Reddit, I have seen people put estimates of the system at ~$15k/citizen/year, but this number doesn't make sense to me. According to the [CBO](https://www.cbo.gov/sites/default/files/cbofiles/attachments/budgetinfographic.pdf), the total spending of the Federal Government in 2011 was $3.6 trillion. There are over 300 million citizens in the US, and 300 million x $15 thousand = $4.5 trillion. That's a bit more than $3.6 trillion, and I doubt UBI would somehow generate an extra trillion dollars plus the money that goes to non-welfare & non-healthcare programs. What am I missing?
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> *Hello, users of CMV! This is a footnote from your moderators. We'd just like to remind you of a couple of things. Firstly, please remember to* ***[read through our rules](http://www.reddit.com/r/changemyview/wiki/rules)***. *If you see a comment that has broken one, it is more effective to report it than downvote it. Speaking of which,* ***[downvotes don't change views](http://www.reddit.com/r/changemyview/wiki/guidelines#wiki_upvoting.2Fdownvoting)****! If you are thinking about submitting a CMV yourself, please have a look through our* ***[popular topics wiki](http://www.reddit.com/r/changemyview/wiki/populartopics)*** *first. Any questions or concerns? Feel free to* ***[message us](http://www.reddit.com/message/compose?to=/r/changemyview)***. *Happy CMVing!* | Let me present a case study of four people, then a social level explanation.
The first of these people is unemployable in the mid 21st century. They have a slight speech impediment that makes them unsuitable compared to other applicants in their field. In our time, they might make hamburgers at a McDonalds, but in the mid 21st century that job has been replaced by the burgermaker machine. They receive their inflation adjusted $15,000 a year, which costs the federal government $15,000 a year. They get to live an okay life.
Next we have a minimum wage worker who makes $15,000 a year as a cashier at the McDonalds of the Future. They work the lunch shift with one other person, and in our time they'd be a manager, but in this time, managing just ordering machines and pulling fries from the automated frymaker, they're replaceable enough to be minimum wage. They'd pay $2000 more in taxes than they do now, but get $15,000. They net $13,000 extra from the program.
Our next candidate is a travelling technician who services burgermakers at McDonald's across the city. He has a masters degree in robotics and works for the burgermaker's manufacturer to provide on site service. He makes $60,000 a year. He'll pay $15,000 more in taxes, and receive $15,000 from the basic income. His life isn't affected by the minimum income one way or another, but he's happy to know that if he gets sick or loses his job that he has something to fall back on and some money to retire with. Obviously he'd prefer to keep making $60,000 than live on $15,000, but it's nice to know he'll have a roof overhead and food on the table if anything goes wrong.
Lastly, we have the businessman who purchased the company that makes the burgermaker. He makes capital gains in excess of 200 million dollars a year. For him, the tax increase is substantial, but like all Americans he receives his $15,000 a year in weekly electronic transfers. For him, this basic income thing is a huge expense that will never pay off... or is it?
Who would eat at a McDonalds in a world where only managers have jobs? How would that business model survive? The minimum income is presented as a solution for a time when permanent unemployment is becoming an ever-expanding reality. It might sound unsustainable for 80% or 90% of the country to be financed by the federal government, but consider why they're unemployed; a machine is doing their work for them. If the same amount of work is being done in 30 years as today but by a tenth as many people, then the same amount of food, housing, and stuff is available to be spread out. We're not here to analyze whether mass unemployment is a good idea - it most certainly is not. We're here to ask if a minimum income is the best solution to that scenario.
For the first time in history, we are using 100% of our planet's resources. When our technology lets us work the same amount of resources with a half, a third, a tenth of the number of people, we're going to reach a point where this is necessary. McDonalds will make the same profit in a future of minimum income that they would today, only instead of paying employees they're paying taxes. This future is largely inevitable, and if we want free market competition to survive then the minimum income will someday be our only option. The only question to face is when. Much of Europe has had double digit unemployment for almost a decade, with no end in sight. It's a matter of your personal opinion when we've come far enough to transition to a minimum income model. But it's the only model that will let us preserve our free market way of life in the face of ever-increasing unemployment, and the only future in which corporations like the Burgermaker company stand any chance at making a profit at all. | 17 | 20 |
CMV: Workers should not be pressured to go back to the office after “vax” and mask mandates are lifted. Remote jobs are the future. | Indeed, we were all rushed into the pandemic’s side effects. Personally, I almost didn’t notice how much had changed because as an artist, I spent most of my time working in isolation without any interactions unless prompted to by a colleague to collaborate or speak at a talk. But for most people who are active employees of an organization, who move from their homes everyday to engage in a work environment to earn their living, it was a crucial change. Everyone was given a “mental and physical break” from work, for the most part. Work now became virtual, as that was the only way to avoid contact and interact with like-minded individuals or colleagues to achieve specific goals. Everything and anything was done virtually using team collaboration and aided apps.
At the rate the world we live in is moving and the rapid frequency of change, it is almost possible that we will all be required to work “online” together to create work and be productive. We have acquired that experience automatically. Our entire lives, money and services and even products now exist in the “meta verse”. With the vax and mask mandates being gradually removed there is no way employers should force individuals to work from the office when there are many ways to collaborate and work on projects virtually.
[Future of Remote jobs in a Post-COVID World](https://www.economicmodeling.com/2021/07/27/future-of-remote-work/) | I mean, in law, for example, it’s pretty useful to have people able to easily talk to each other.
That doesn’t mean everyone needs to be in every day, but it’s not sensible to have people going to court without having come to the office to meet the client and talk about the case.
Moreover, in law, like in a lot of fields, being remote meant working 24/7. Having office hours helps set boundaries. | 338 | 1,709 |
How do scientists determine what a planet core is made of ? | There are no direct methods, but there are several indirect methods that we can use. First off, it depends on the kind of planet you are studying.
Let’s start with gas giants like Jupiter. Our first step would be to look at the moons circling it, from their orbits we can get a really good guess at what the overall mass of Jupiter must be. Next, from regular observations we can estimate it’s size. This gives us a density estimate which puts us in the ballpark of what kind of materials we can expect.
Additionally, we can get measurements of its magnetic field and surface make-up from probes. Earth’s own magnetic field is created primarily because our liquid core flows and spins. As magnetic fields can arise from the movement of electrons, a good explanation for the existence of our magnetic field is a hot, liquid core undergoing convection. We can apply the same reasoning to many planets, if it has a strong magnetic field it is possible that it has a very active core and so we might initially expect things to be liquid down there.
For terrestrial planets there’s one more trick we can use: seismic activity. Since waves travel differently through solids and liquids we can guess at what kind of materials might be under the surface. This gets more useful if you have many monitoring stations in different areas to all track the same seismic event.
Finally we can begin to play a sort of detective game where we deduce elements and structure from what we know about our solar system, physical properties of the planets, and the principles of physics and chemistry. Building off all of this knowledge, one paper used Density Functional Theory, a result of quantum mechanics, to estimate the behavior of iron inside the Earth’s core. Using this analysis they concluded the temperature of the core should be within 5300K-5700K and that there is likely between 8%-13% oxygen in the outer core.
Scientists have done an amazing job using basic physical principles to extrapolate what might be happening in labs millions of miles away from their chalkboards.
Sources:
[1] Goldstein, classical mechanics ch. 3
[2] Geophysical Research Letters, Seismic anisotropy in the Earth's innermost inner core: Testing structural models against mineral physics predictions, B. Romanowicz, et al.
[3] Griffiths, introduction to electrodynamics ch. 7
[4] contemporary physics, temperature and composition of the earths core, D. Alfé, et al. | 14 | 17 |
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ELI5: Quantum physics experiments suggest that reality doesn't exist until it is measured or observed. What the heck? | Observed does not mean by a sentient being. Observed simply means interaction in this context.
Here's an analogy:
Say you're measuring the temperature of water with a thermometer that starts off with a temperature, say 20C, and the water you're measuring has a temperature of 50C.
If you're measuring a pool, it doesn't matter. If you're measuring a tiny droplet of water, the heat of the thermometer will effect the temperature of the water!
It's like that for quantum particles. In order to measure them, we have to interact with them, which then collapses the waveform.
Note that the Heisenberg uncertainty principle has nothing to do with this. | 15 | 25 |
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why arent non normal distributions emphasized more in studies? | i dont work in science, mostly economics and business data - i have almost never seen NON right skewed distributions. i mean, everything in the business space seems to start at 0 with big outliers. does that mean we are always supposed to use nonparametric methods or something? its just crazy how ubiquitous normal dists were in school and i NEVER see them. | A large number of hypothesis tests do not require normally distributed **data**- they require approximately normally distributed **sampling distributions**, or **residuals**, or **conditional distributions** of some sort. For example, in a paired t test the data does not have to be normally distributed, it is the differences between the pairs that needs to be (approximately) normally distributed, but even then it is really the distribution of sample means that needs to be approximately normal. This is why textbooks (erroneously) talk about the central limit theorem (erroneous because the CLT only helps you with infinite sample sizes). However, we have lots of other results that tell us that in most "nice" data, sampling distributions become close enough to normally distributed with smallish, finite sample sizes.
Even for the tests that explicitly "require" normally distributed data, most of these are very robust to moderate amounts of skewness and kurtosis. | 42 | 32 |
Why is the quantization of gravity so hard to prove? If mass if quantized, why does it not follow that gravity is also quantized? | >If mass if quantized, why does it not follow that gravity is also quantized?
Mass isn't quantized. There is no reason, a priori, why a particle cannot have any value for its mass. Indeed, in the Standard Model, the masses of the fermions are parameters that must be fixed according to experiment.
Also, energy is not quantized either; this is a frequent misconception. Electromagnetic waves are quantized into packets of energy, proportional to Planck's constant and the wavelength of the EM wave. Planck's constant is constant, but an EM wave can have *any* wavelength. To say that it is quantized doesn't necessarily mean that only certain amounts of energy are allowed (although for some systems, like atoms, that may be true); rather, it means that EM waves interact with matter via discrete packets of (any particular value of) energy -- which we call photons.
>Why is the quantization of gravity so hard to prove?
For two main reasons: (1) gravity is such a weak force that we can't even directly detect coherent gravitational waves (which, if gravity is quantized, would be made up of many, many gravitons); so far we only have indirect evidence of gravitational waves. That makes it very hard to "prove" (edit: i.e. demonstrate to arbitrary level of accuracy) things about gravity, since we can't yet measure those waves directly. Secondly, (2) our current technique for successfully quantizing the other forces doesn't quite work for gravity. If gravity is quantized, its quantization must be described through some other mathematical framework besides renormalization -- one which we haven't figured out yet.
Also FYI, it's worth mentioning that the recent BICEP2 observation of primordial B-mode polarization in the CMB, if it is independently confirmed, *would* constitute ~~proof~~ demonstration to a high level of accuracy that gravity is quantized in nature. Though recently there has been some concern that the BICEP2 result might be explainable via polarization due to dust clouds in space. It remains to be seen whether the result will hold up to peer review, or be confirmed by another experiment.
Hope that helps! | 22 | 17 |
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ELI5: why are train tracks filled with stones? | Isn't that extremely dangerous if one of the stones gets on the track?
#Answer below
##Do trains get derailed by a stone or a coin on the track?
No, trains do net get derailed by stones on the tracks. That's mostly because trains are fucking heavy and move with such power that stones, coins, etc just get crushed!
##Why are train tracks filled with anything anyways?
* Distributes the weight of the track evenly
* Prevents water from getting into the ground » making it unstable
* Keeps the tracks in place
##Why stones and not any other option?
* Keeps out vegetation
* Stones are cheap
* Low maintenance
Thanks to every contributor :) | Those stones (called track ballast) serve four primary purposes:
- Load-bearing (it distributes and bears the weight of the railroad ties)
- Facilitation of water drainage away from the ties
- Keeps out vegetation that could interfere with the structure of the track
- Helps keep the ties in place | 4,877 | 4,858 |
ELI5 how do arm prosthetics work especially when you have almost your whole arm gone? | Sensors are placed to pick up signals both electronically and physically from remaining muscle structures left around the stump
These are used to actuate the various artificial muscles of the prosthetic either through mechanical action or electronic/pneumatic actuators | 14 | 21 |
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ELI5: how a double-blind study works, and why it is considered so reliable | Double-blind studies are usually used in medicine. They are to control for the placebo effect.
Let's say you have a new drug and you want to test how well it treats a disease. So, you get a whole bunch of patients with that disease. You give half of them the new drug and half of them a sugar pill (you could also give them the old drug if you want to compare against that instead). The patient doesn't know which pill they got, so that's the first blind. The second blind is that the doctor that gave them the pill also doesn't know which pill they got.
The reason for the second blind is that the doctor's actions might influence the patient. So, if neither the patient nor the doctor know whether they got the new drug or not you can be sure that any effects are from the drug itself and not from the placebo effect. | 38 | 53 |
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CMV: Palestinian refugees are held to different legal standards than all other refugees, and this is blatantly unjustified and unjust. | All refugees are held to different standards based on where they are from and what country they are attempting to flee to. Despite the UNs efforts there is no uniform way of handling refugees, nor should there be. No nation is required to accept refugees and they are fully entitled to set whatever rules they want for refugees or other immigrants to enter their country. | 23 | 125 |
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How Does A Towel Gaining/Losing Water Function On A Atomic Level | I was thinking about this early, but couldn't think of a reason that satiated me. My basic hypothesis was that, the towel functions like a net and "catches" the water and the water "escapes" when it evaporates into a gas.
I don't feel quite satisfied with this answer though and would like a tad more elaboration/correction.
| Atomic level is too small, you need to look at molecular or even the micro scale for that phenomena.
A towel is designed so that it has a relatively porous structure with a lot of surface area and interconnected pathways. These porous channels allow for water to be wicked away from your skin and travel into the cloth of the towel, using capillary action the same way a candle wick works. The water then sits in the wet towel using intermolecular interactions with the towel fibers.
Drying the towel happens through normal evaporation. The high surface area of the towel means there is quite a bit of surface area over which evaporation can happen, so towels can dry relatively quickly (compared to the same amount of water in another container). | 52 | 105 |
ELI5: Why do we continue using the existing credit card technology over all these years despite them being so prone to digital theft and insecure? | Some say that chip based cards offer improved security, but finally everything ends to the 16 digit number, the 3or4 digit CVV number and the expiry date. And as we have seen in the case of wikileaks, the limited number of companies like Visa, MasterCard that control payments can also force a financial blockade. So why do we still employ the credit card instead of using a password based method or a real time payment approval technique or something. I don't want to use these insecure credit cards, but people tell me that my credit score will not improve unless I start using a credit card. | 1. From a consumer perspective, credit cards are way more secure than cash. If someone steals your credit card (or credit card data), in the US, you are liable for at most $50 in charges, and all of the major credit card companies will even cover that for you. So sure, it's insecure from a technical perspective. But as long as you check your statement for unauthorized charges every month, you don't have to care about that.
2. There has to be something connecting the merchant to the bank that has the money. Right now, a merchant just needs to accept Visa and Mastercard plus Discover and American Express (which run their own banks) and they can accept payments from pretty much every bank in the country. Get rid of that and each merchant would need to negotiate with each bank independently. Which is fine for Bank of America, Chase, HSBC, Deutche Bank, and maybe a few others, but smaller banks and credit unions are out of luck unless they form a consortium that would be jointly accepted (which is what happened originally when Barclaycard, BankAmericard, Chargex, and a few others combined to form Visa). We could switch to a more secure system (and we are starting to, with payment platforms like Apple Pay and Android Pay), but it wouldn't get rid of the need for someone to handle connecting a large number of merchants to a large number of banks.
3. Your credit score will not improve until you take out a loan and pay it off on time- that's really the best way for lenders to see that you're good for the money. And the best way to take out a large number of small loans and pay them off on time is to use a credit card. | 40 | 153 |
AskScience AMA Series: I'm Patrick Long, M.D. and I am a geneticist with a specific interest in the adult genetics field. I just started an adult genetics clinic, SequenceMD, to address the needs of this widely underserved population. AMA! | Hi Reddit! SequenceMD team here: we are Dr. Patrick Long and genetic counselor, Alisha. We're here to answer any questions you may have about medical genetics or... anything!
We'll start by answering our own question: why adult genetics? Genetic testing is a routine part of the diagnostic workup for many childhood onset disorders including cerebral palsy, developmental delay, movement disorders, etc. Your genes don't change when you turn 18, but it's still not standard of care to test adults living with these disorders. In some cases, genetic testing can reveal treatment options, management guidelines, or preventative care, that is very much relevant to adults. Most geneticists in the United States are pediatric focused. Adults who are able to see a geneticist may face long wait lists or be denied testing. We believe that genetic testing should be an accessible choice for those who are interested.
We'll be on at 10AM MDT (12 PM EDT, 16 UT), AUA!
Username: /u/SequenceMD | One of the major challenges in this field is patient confidentiality, and how genetic information from one family member necessarily gives information about others. For example, a child testing positive for trinucleotide repeats in Huntingdon's disease means that the parent will have it, even if they're not symptomatic and even if they didn't want to know one way or the other. How do you deal with privacy concerns like these? | 83 | 1,270 |
ELI5: How are people with dementia able to have "good days" when they remember people or events that they wouldn't normally recall? |
Your brain is always getting information from the environment around you: what you hear people say, the color of the walls, what you see people do, the feeling of your clothes against your skin, what cards you have in your hand when playing a card game, and so on. Not all of that information is important. When you're playing a card game with friends, knowing what cards you have and hearing when your friend says it's your turn is useful, but the fact that the wall is white isn't useful information. Luckily, there is a part of your brain that decides what information is important, and filters out the extra info so you can concentrate.
In patients with dementia, that part of the brain has been damaged- it's not completely useless, but it's much weaker than it would be in a healthy person. Basically, these patients are overwhelmed with information, but they have trouble figuring out what information is important and what that information means. They may see white walls and think it means they are in their mother's house, or they may see the cards and realize they need to lay down an ace to win.
There's no way to know for sure when they will pick up on the right information, but scientists do have some ideas of what causes them to be more aware. How aware (lucid) a person is can vary based on tiredness, mood, changes in physical health, what drugs/hormones are in their body, the environment around them, how other people are acting, etc.
For example, let's say Ruby is in the middle stages of dementia and normally isn't aware of where she is. Her in-home caregiver decides to take her on a car ride one morning and accidentally begins to back up too close to the edge of a drop off, and Ruby suddenly shouts, "If you don't pull forward we're gonna die!" This is likely because 1) it is morning and Ruby is not yet tired, meaning the part of her brain that is damaged is not yet worn out from a busy day of trying to make sense of things, and 2) this situation is especially dangerous, meaning that other parts of Ruby's brain would recognize that this is a threat and send out hormones that improves how well the damaged part of her brain works.
In the same vein, being very tired or in a dull environment could cause a person to be less aware.
Many experts believe that a lucid day (good day) happens when the "perfect storm" of these factors occur. | 63 | 122 |
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ELI5: What makes mathematics factual? | The ELI5 answer is that math is more or less like a game. Mathematics is carried out by a predefined set of rules on a predefined set of objects. Because the game never changes, the allowable moves never change, and so the possible outcomes never change. Any situation in which the rules of the game are allowed is therefore subject to the outcomes mathematics applies to. So things like basic physics which work on just adding and multiplying numbers representing physical quantities are essentially universal because they are a situation in which you are playing the game, just using different words for the same things.
​
Sometimes, the rules of the game do change. This can happen because we find out the game is broken (as in e.g. the crisis of naive set theory), and sometimes it happens because we find out that some other games are also cool or useful, or less controversial. Not all mathematicians agree that we *should* be playing the game that we are, and so they play slightly different games, but this doesn't effect the main allowable moves of the game. The basic things like + and x are still the same, it's that there are some weird edge cases involving things like ungodly huge infinities and what you can and can't do with them that some people object to. | 36 | 27 |
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[WH40k] What does the recruiting process for the space marine chapters entail? | What qualities do they look for? Who does the recruiting? Do the various chapters look for different things? | It varies by the chapter but in general they're all looking for strong young men who already represent the very best their people have to offer. A lot of chapters make their home on worlds where life is not easy. Environmental hardship, frequent warfare, it doesn't matter as long as there's a natural selection going on to make the natives hard and strong.
Most chapters have a periodic recruitment run every decade or every few decades. Some chapters have the locals organise contests where their fittest men compete in a variety of events under the watchful eyes of space marines. Other chapters simply look for men who have been successful in battle or who have other achievements of physical excellence.
As long as the candidates meet the physical requirements, the marines care little about their personalities. Psycho conditioning takes care of that.
For example the blood angels recruit on Baal, an irradiated wasteland of a planet. The Space Hulk game describes the various members of the terminator squad and they're quite diverse. One man used to be a psychotic gang member while another was a wasteland nomad. One of them is an artist while yet another is so dull witted that the rest of the squad jokes he's a servitor promoted by mistake.
In the end, the main quality candidates need is the physical peak condition to survive the surgeries, gene therapy, psychoconditioning and training that brings them from initiate to neophyte to fully fledged marine. Even the exemplary men selected by the marines usually don't survive. | 35 | 26 |
Why are water molecules curved? | Why don't the charges of the hydrogen repel each other and hold the molecule in a straight line? | The geometry of a water molecule is determined by the outermost electrons around the oxygen. You have two electrons in each of the bonds between oxygen and water, but you also have two pairs of electrons that oxygen holds onto all on its own. If we just had the two electron groups from the bonds you would be right, the hydrogens would be 180 degrees straight across from each other in order to give the electrons as much space as possible, but since we also have those two extra pairs of electrons from the oxygen, we have to make space for those two. This ends up meaning that there is only 109.5 degrees between each of those electron groups. Hope that helps! | 243 | 259 |
ELI5: What does it mean that the Carbon in our atmosphere has passed the point of no return? | In this newly released article it states Earth is passed the point of no return and we're all fucked basically. Are we really that screwed over and is there really no way to reverse such a fuck up?
EDIT: http://www.complex.com/life/2016/09/enjoy-earth-while-it-lasts-atmospheric-carbon-levels-pass-point-no-return | Scientists anticipate that there are certain feedback loops, which mean the warmer it gets, the easier it is to get warmer.
Imagine sitting in a waggon with rusty wheels. The wheels are so locked up that even though you are on a slight decline you aren't moving. You add a few books to the wagon for more weight and now you start to roll a bit. But you have a little bike style handbrake set up and can keep.movimg down the hill slowly.
But the more you do, the more rust starts to get knocked off the wheels. It starts to roll faster. You squeeze the break more... but the faster you go, the hotter the break becomes and the less effective its grip. So you move faster and faster. At this point you throw out the books hoping to return to how things were at the top of the hill, but its too late.
Feedback loops such as melted water catching more sunlight than ice are one such reason some scientists are saying that we passed the tipping point where throwing out the books (cutting our emissions) won't get us back to the top of the hill. That doesnt mean we should keep asking people to push us faster though.
The other thing to remember is that the earth will be fine. The earth doesn't care if the US becomes a dessert and canada becomes an oasis. Earth doesn't care if florida is above or below water. But people, government, individuals have built certain ways of life, certain standards of living, certain settlement patterns, certain alliances etc. These adapt far slower than the milenia and millions of years that earth gives itself to respond. | 61 | 56 |
Why can't we see well underwater? What is different about the eyes of aquatic animals? | The key difference is in the lens of the eye that handles focusing the image onto the retina. When focusing, the "work" is done as light transitions from one material to another, as the index of refraction changes, which causes the light to bend.
Outside the water, this is (roughly) air -> lens -> vitreous humor (the fluid in most of the eye). Underwater, the air is water instead, and the difference between the index of refraction of air and the material of the lens and water and the material of the lens is much greater. So outside the water you need a much less round lens to do the focusing.
Human eyes are adapted to focus well in the air, while the eyes of aquatic creatures do better under water. This is also why if you put goggles on, you can focus well underwater. | 91 | 235 |
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How does Quantum Entanglement work? | How do the particles that are entangled manage to always do the opposite of the second one? Are they communicating with each other if so how? Otherwise is it some kind of force? | There is no known mechanism by which the particles "send a message" to one another. The phenomenon is the result of creating a system of two or more particles whose wavefunctions depend upon one another. By measuring an aspect of one particle, its wavefunction is collapsed to known value, which causes the other particle's wavefunction to be known as the other value.
For example, take two electrons that are known to have a total spin of 0. Each electron has a 50% chance of being measured to be either spin-up or spin-down. If you separate them, each will still have a 50% chance.
However, if you separate them without changing their spin, and then measure electron 1 to be spin-up, then you will find that electron 2 is spin-down 100% of the time. How does it know that electron 1 is spin-up? Nobody really knows. It's an active area of research, however. | 1,819 | 3,055 |
Advice for PhD student asked to "modify data" by adviser | My friend is a STEM PhD student, whose adviser asked him to modify data for a publication. Note that this version of the paper has not yet been submitted to a journal. The student was asked by the adviser to modify data in a couple ways.
First, is scaling raw data by multiple orders of magnitude, and then presenting the scaled data as if it was raw data, without any reference to a scaling factor.
Second, is more complicated. It involves taking the difference between two signals, shifting the difference by an offset, setting the new values to zero if below a threshold, shifting these values around in time, and then reconstructing the original two signals using these processed values. The processed results look significantly "better" than the raw data. The paper has no reference to the processing of these signals, and it is implied that they are raw data.
What should the student do? He has already complained to the adviser, but adviser dismissed this type of modification as "normal."
My friend hesitates to push the issue further, because another PhD student in his lab is trying to defend a thesis based on this work, and he does not want to prevent the other student from graduating. Both my friend and this other PhD student (who are both co-first-authors of this paper) have zero publications (first author or otherwise).
If the paper is under review at a top journal, and then the other PhD student will look better during their thesis defense. The student thinks that the paper will almost certainly be rejected because the paper is riddled with other problems (lack of clarity, odd nonstandard ways of defining things, leaving out information necessary to reproduce the data - see a pattern here?). My friend thinks that after the paper is rejected, then they can redo the experiments legitimately, or be more transparent about the data modification.
What should my friend do?
Some more background: Both my friend and his fellow labmate are 5 years into their PhDs. His research group has not published a single paper in multiple years, despite normal and consistent effort by the PI and many PhD students. The overall work is legitimate, but not groundbreaking, but the PI refuses to submit it to anything below Nature, Science, and their respective subjournals. The paper has already been rejected \~5 times, and they are resubmitting the paper to a top journal that rejected it. In the most recent version of the paper, the PI greatly inflated the claims of the paper compared to previous versions.
In general, the research has been hindered by the PI. He is a micromanager, and treats all PhD students like technicians. He meets with each student \~3 times a day, makes all creative decisions, and does not allow his students to even write their own papers (the paper above in question was written entirely by the PI). He often makes irrational decisions, and aggressively defends them, resorting to yelling and personal insults. The list goes on. Overall, the PhD experience has been described a nightmare for my friend, and he is desperately trying to graduate, even if it means with no publications. | From an outside perspective, that sounds really sketchy--but it might be worth trying the get in contact with someone who works in a very closely-related field (perhaps someone else in the department?) just to ask if the proposed alterations are common practice. Obviously fraudulent data of any kind is a huge problem, but it is worth attempting to confirm that it's fraudulent before raising alarms. | 68 | 70 |
CMV: Younger generations have it harder than their parents |
At least when it comes to making their way in the world. A few decades ago, it was possible to live a fairly comfortable lifestyle on a single income. My Dad had classmates who started working at the mill out of high school, and while they worked darned hard, they made a decent income.
Today, it's all but impossible to live on a single income, with more being considered necessary and less job opportunity. Took me 2 years of constant searching to find my current job, and too many bosses will just suck you dry and discard you, with no real prospects for improvement.
Even college has become unaffordable for many. 50 years ago, you could get a degree, leading to a good job without being crushed in debt. In the 1990s, it would get you a decent job, but you'd be heavily in debt. Today, all your degree might get you is a job at McDonalds.
Yes, a lot of people in their 20s and even 30s are still living at home, often attributed to "They don't want to work hard." Well, there are fewer jobs available, it takes longer to find one, and job security has become a distant memory. Both parents working is now an absolute requirement, with women unable to stay home even if they'd like to. (And yes, this applies to the father as well)
What I often notice is they assume the world works the same way as it did when they were younger, not understanding how much things have changed over the past few decades. Usually, it's: "Just work hard, dedicate yourself, and you'll go far!" All too often, that's not what ends up happening.
I'd even say kids growing up now are going to have it harder than us. After 2007-2008, the economy rebounded only slowly, and now we've got Covid to deal with. Who knows how long that's going to last? They've lost a year of education, sometimes two, forced to deal with isolation, and having to enter a still-smaller workforce. | A lot of what you are saying is correct in terms of finding jobs and education and paying for it.
However, your parents and grandparents had no support system to cope with bullying and mental health issues. They were far less healthy and had to breathe cigarette smoke constantly. They could do little if they experienced abuse from their parents or romantic partners.
Life for racial and sexual minorities and women gets progressively worse as you go back in time (unless you go way back).
It’s definitely not all gumdrops and rainbows today but it’s better than the past in many ways too. | 39 | 33 |
Why do legumes (mainly thinking about peanuts and soybeans) seem to be more allergenic than other foods? | Partly due to protein content - generally, proteins are more likely to cause allergy than other compounds.
This combines with a genetic component which suggests that individuals with certain allergies are more likely to have children with those allergies, so common allergies remain common because of genetic predisposition (where those genes came from originally is unclear).
Lastly, lack of exposure appears to play a role. Ie: because peanuts and eggs are a common allergen, parents are less likely to expose their kids to them, which in turn means they're more likely to develop that allergy. | 208 | 377 |
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How can certain bacteria and viruses be deadly to one species but completely harmless to another? | Edit: Wow. Thank you all for the great answers! | You could potentially get many answers to this question! One example is if the pathogen's surface proteins recognizing specific cellular receptors that exist on one species but not the other. If they cannot recognize and attach to the cell, they are not infectious. Another variation is the immunity of the species and whether it can keep the pathogen in check. For example, bats have sophisticated anti-viral mechanisms that keep them safe from otherwise deadly viruses (like SARS!).
Yet another variation is the part of the world the host lives in; many pathogens thrive in a specific environment, so it makes sense that they would adapt to recognize hosts that live in a similar environment.
The short answer to your question is evolution. The host and pathogen co-evolve together which reinforces their relationship. Occasionally, however, the pathogen can mutate and cross species, like what happened with SIV and HIV. | 973 | 3,070 |
ELI5: How does "weed and feed" know the difference between the grass it should feed and the weeds it should kill? | Different organisms have different physiologies. Same way chocolate is fine for human consumption, but will kill dogs. Monocots like grasses have different cellular components than dicots like dandelions and other types of weeds and herbicides can be designed to differentiate them. | 40 | 46 |
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Why don't greenhouse gases reflect just as much incoming sunlight as they trap? | The common explanation of greenhouse gases is that sunlight that would bounce off the Earth out into space instead bounces off the greenhouse gas, trapping that heat on Earth.
But if greenhouse gases simply reflect solar radiation, wouldn't they also reflect from the "outside", too, thus preventing solar radiation from reaching the Earth in the first place? | Greenhouse gasses, like the glass of their namesake, are transparent to most of the visible light spectrum, but more absorbent of infrared light (ie heat radiation).
When visible light passes through the atmosphere and hits the earth, it warms up the earth, which then re-radiates that energy to space as infrared.
So hence the greenhouse gasses pass through the visible light on the way down, but block the infrared from getting back out again, so energy is trapped in the atmosphere. | 48 | 26 |
An article is coming out that might make my thesis obsolete. I don't know what to do. | **[UPDATE HERE]**(https://www.reddit.com/r/AskAcademia/comments/hmagml/update_an_article_is_coming_out_that_might_make/?)
My advisor is currently unreachable, so I'm asking you guys here.
I'm currently working on my master's thesis which is a systematic review. Today I happened to search the systematic review protocols database for something similar to what I'm doing and just found out that a protocol was registered literally yesterday for a review **exactly the same** as mine. It also says that it should be completed by the end of this month, which is way ahead of my thesis.
Now what? I never even imagined this could happen. Does all my work become obsolete? Do I have to start over? | Congratulations! You have just shown that you can generate scholarly questions that other people find interesting. Empirical evidence that at least 1 person is interested in your thesis work, more than many people can unequivocally say.
Take the next hour to freak out about it, it still sucks because you feel like your thesis is that much harder now, and it may be. Your advisor will be able to give you advice, only they are the ones who can say how much this development will matter for your thesis. It sounds like you are not completing it within the month, so there are no rush to come to a decision in the next 24 hours. You have time.
You don't have to start over. You may have to tweak it depending on how exactly the same it is and how close to being complete you are. But all the work you have done isn't worthless. | 131 | 59 |
Can anyone give examples of economic systems that are very different to what we are used to? | I was reading [Legal Systems Very Different From Ours](http://www.daviddfriedman.com/Academic/Course_Pages/legal_systems_very_different_12/LegalSystemsDraft.html) and it was interesting to see systems that are cohesive and worked in ways that I'm not used to. I guess I'm just looking for more of the same in different fields. Bonus points for anything that falls outside of the Capitalist ~ Communist spectrum, but novelty within the spectrum is still encouraged. | I would recommend reading "The Gift" by Mauss. The gift exchange system described in this book is not an economic system in the usual sense, since only a small portion of all the consumption goods are exchanged in this way, but is a very interesting market.
It's rather difficult to summarize, but some hallmarks of the gift exchange systems described are the exchange of gifts to purchase social prestige and the need to return larger and more precious gifts to the original gifter. | 43 | 93 |
Reviewing a bad book (Humanities) | Has anyone got any pointers for writing a bad book review?
My honest opinion on the book I've got to review is that the research is dated, poorly argued, misses several key areas and is full of theoretical flaws (anachronisms, misundertanding of manuscript traditions, use of old transations etc). The book is also extremely poorly edited: its full of typos, a chapter is misnumbered and a chapter may possibly be missing all together (its hard to tell as the signposts between chapters are quite poor).
I'd really rather not do it but thats not really an option. I've written the review as objectively as possible but its still nothing like any academic book review I've read - does anybody have any pointers for writing an honest and objective review that won't be a hatchet job? | Are you doing this review for the publisher, reviewing a manuscript that might get published, or are you reviewing (in an article to be published in a journal) a book that has already been published?
If it's the former, then have at it. The publisher needs to know whether or not to publish, and your responses can help the writer(s) strengthen the manuscript to resend out for review.
If it's the latter... Sigh. You might then try to figure out how your review can be most useful to the readers of the journal in which the review will go, since -- in this case -- they are your audience now, not the publisher or the writer(s). It sounds then as though you could use the review to ask questions about how this book ever made it through the peer review process and to emphasize the importance of chapter functions, etc., while also pointing to how the manuscript itself falls short.
You could also perhaps use this as an opportunity to write about research in the same area that does to what it should, in order to have that be the positive side of your writing, so that what you write isn't completely negative.
But please do let *your* readers know why you think this book is not worth their time; that's the whole point of doing what you are doing and your work helps us all strive toward more integrity. It sucks when you can't do a positive review, but sometimes.... | 15 | 27 |
ELI5: How come people around the world all use the same math, but we all speak different languages? | If you think about it, math is the language that helps humans understand the universe. Different aspects of math originated from different places around the globe. How come math has been able to stay globally consistent, but spoken languages are all different depending on where you live?
I hope my question makes sense. Thanks in advance! | Math is way more universal than language. You can change words and their definitions, but you can't change logic.
Although the old Babylonians split numbers in steps of 12 rather than 10.
Most peoples split them into steps of 10 because that's how many fingers we have. | 333 | 290 |
What bonds my atoms to my body? Why don't they merge with this chair I'm sitting on? | Atoms in molecules bond because they want to achieve a lower energy state. Most of chemistry is the study of why exactly atoms bond and for molecules they way that they do. So, the really simplistic answer is that the molecules in your cells are more attracted to each other than they are to other objects. Solid objects are usually attracted or formed in a way that all the particles stick together and are rigidly kept in line. | 12 | 32 |
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[Classic Doctor Who] was the TARDIS ever depicted as actually flying the way it sometimes is in modern Doctor Who? | I'm well-versed in the modern episodes, but have only seen a handful of the classics. In the current series the TARDIS is always described as disappearing one place and appearing somewhere else instantaneously, but we randomly have images of it actually flying in spacing or flying through the time vortex. Was it ever depicted this way in the past? Does anyone have an in-universe explanation why sometimes it flies and sometimes it instantly changes places? | A few factors in play.
Timeframe perspective - When the TARDIS appears to vanish or appear from nowhere it's actually the TARDIS translating to/from the Time vortex. The view you see is locked to your (the camera's) timeframe, which the TARDIS is entering or leaving.
Being 'part of events' - When we see the TARDIS 'in flight' like a more "conventional" spacecraft its not changing its position in time, only in space. As the Doctor remarks once "short hops are difficult" so if he doesn't need to move through time it's usually easier to just fly the TARDIS from point A to point B instead of accessing the Time vortex, assuming he landed in the open to begin with and not in a structure. | 31 | 76 |
What do living organisms do to prevent bacteria from decomposing them that dead organisms are unable to do? | Basically why does decomposition begin after death? | Our bodies form many barriers that stop bacteria from entering our tissues. Even though we have bacteria on our skin, in our gut and many other places, we have very specialized cells lining these areas. They defend our bodies by numerous mechanisms: secretions that capture bacteria, cilia that push bacteria away from sensitive areas, VERY tight connections between cells that does not allow the passage of bacteria, and defence cells that ingest bacteria and bind antigens are some of these defences. When we die, our cells will also die as our heart stops and oxygen is no longer being delivered to the tissues. as the cells die, they can no longer perform these defensive functions. they may also lyse, releasing proteins and other molecules which the bacteria can thrive on. Consequently the bacteria and other microbes can cross our barriers and invade our bodies. | 20 | 25 |
ELI5: Wheels, wagons, and chariots were invented thousands of years ago. Why, then, did it take all the way until the 1800s for the bicycle to make its debut? | Materials, manufacturing techniques, and road conditions.
We had to reach a point where metallurgy and materials made a bicycle beneficial. You can make a bike out of wood and metal, but its gonna be extremely heavy, prone to breaking, and difficult to ride. Without extremely smooth solid roads you would be slamming and jarring the wheels and frame constantly. | 43 | 27 |
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How clearly can we see objects in other galaxies? | I have always been curious as to just what kind of details we can see, and what can only be theorized. For instance, we can count how many moons Saturn has, but can we tell the same for a planet in another solar system? To my understanding it would really come down to just how much light is being reflected from these planets and moons. I guess I don't really have a direct and clear cut question, so I suppose I'll just ask this, what criteria is needed for us to be able to know there is an object in space? | Our telescope resolution is what limits us to see detail on objects in other galaxies. An object can be incredibly bright, but unless the optics you're using have the proper resolving power, it will look like a big bright blur.
Telescopes have specific resolution that depend on their size and ability to see beyond the turbulent atmosphere. Hubble's resolution is about 0.1 arcseconds. An arcsecond is the *angle* an object in space subtends -- that angle can be converted very easily to a "real size" if you know how far away the object is. So for the galaxy M51, which is ~ 7 Mpc away, HST can resolve objects that are as small as (0.1 arcsec)(7 Mpc)/206265 = 3.394 x 10^-6 Mpc, or 7 x 10^5 AU, where 1 AU = the distance between the Sun and the Earth.
So HST would not be able to "separate" the Earth and the Sun (or the whole solar system for that matter), and in its optics the system would appear as a single dot.
EDIT: clarification to the last sentence... "HST would not be able to "separate" the Earth and the Sun *at the distance of M51*" | 10 | 16 |
CMV I believe affirmative action should be based on wealth not race | I do not believe race to be a dominating factor if someone needs additional help and support that affirmative action brings. In fact I believe it promotes racism and damages race relations.
However I do believe that coming from a poor family gives you a distinct disadvantage in life compared to being from a rich family. If you come from a well off family you have more resources at your disposal then someone from poverty.
Growing up in poverty also puts people in close contact with criminal activity and other poor influences.
So I believe that the "helping hand" should exist to give these people a leg up.
I know there is a correlation between minorities and being from a poor income family. So even having the system based on families income levels will still result in primarily monitories receiving the benefits.
I don't see an issue with this because it still directing the help towards the people who actually need it. People who grew up in poverty.
I honestly feel that a Caucasian male who grew up in poverty is at a disadvantage compared to an African american women who grew up middle class.
| If you consider universities, the most common users of affirmative action, the problem with your view is that in conflates two disadvantages: access and acceptance. Consider two comparisons:
A middle class white student and a middle class black student apply to the same university with the same CV. Absent affirmative action the white student is more likely to be accepted.
A middle class white student and a poor white student apply to the same university with identical CV's. Both are equally likely to be accepted, but only one will have better *access* because many poor students will be unable to go. Affirmative actions doesn't really address this. Most financial need based scholarships, bursaries and loans you can get are race neutral.
There's also the problem of absence. The absence of people of colour from important institutions (the government, universities and the press) changes both how they function, how they're seen and how those people are treated, all for the worse.
Your view solves one of these problems, the status quo addresses both.
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If the liver can regrow from a piece in 30 days, then why isn't liver scarring treated by removing a bit and letting it regrow? | Liver is an organ that is known for its regenerative ability and therefore able to take a lot of abuse before it's scarred beyond repair.
One of the reasons that your suggestion isn't a standard treatment is that liver is highly vascularized organ and even a small nick can cause severe bleeding. Also, liver scarring is diffuse -- all over the organ -- and so, it wouldn't be possible to just cut out a section.
However, there are instances of liver transplants where a piece of healthy liver is transplanted into someone else and it will grow in the new home (body). | 130 | 240 |
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ELI5: Why are there typical breakfast foods and dinner foods? Is there a biological reason where we want certain nutrients at different points in the day or is it just a social construct? | Imagine you are are a preindustrial farmer. You get up before dawn, toil in the field all day, then go back home when it gets dark.
For breakfast, you want something hot that will give you a lot of energy, but can be prepared quickly.
For lunch, you want a cold meal you can take with you and eat when you get hungry.
For dinner, you have time between sunset and bedtime, so you can take a little longer, and have something nice while socializing with friends and family.
The pattern of necessity has become ingrained in our culture, so we consider certain foods to be appropriate for certain meal, long after the original reasons were forgotten. | 46 | 38 |
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ELI5: How do some stereo sounds sound like they are coming from both sides rather than the middle? | Example: when listening to music on headphones, the vocal is usually in the center, inside your head, whereas instruments sound like they're outside your head on both sides, even though the volume is the same in both channels. | So the way our brains interpret the direction a sound is coming from is to listen for differences in the sounds reaching each ear. So when stereo speakers (placed at an equal distance) are playing the EXACT same sound, our brain interprets that as coming from directly in front of us.
When an audio engineer is mixing music, it is sometime desirable to have some instruments sound like they are coming from the sides, but not necessarily one side or the other. To accomplish this, they have to make one side (either the left or the right channel) SLIGHTLY different from the other.
One way this is accomplished is by a “Stereo Spread” which will take a stereo audio file and spread certain sections of the frequency band to either the left or right. That way the left speaker will be playing some of the frequency bands, and the right speaker will be playing the other frequency bands of the same sound.
The other way this can be accomplished is by using the Haas effect. This is done by simply “delaying” one of the sides (either the left or right channel) by up to about 30 milliseconds; so one side is playing the exact same sound as the other side, but just slightly later than the other. By only delaying it as much as 30ms, our brain doesn’t detect it as being “out of time” and can barely tell the difference. However our brain DOES definitely hear two separate and distinct sounds in each ear making it interpret the sounds as coming from each side instead of directly in front of us. | 28 | 16 |
ELI5: What's with (what seems like) the sudden increase of gluten free foods, restaurants, diets, etc.? | Is there really an increase of people with Celiac Disease? Or are there benefits to being gluten free? | There are a few people with Celiac Disease, for whom a gluten-free diet is medically necessary. Beyond that, it's just a fad. Companies advertise products as gluten-free (gluten-free water!, gluten-free tupperware!) in order to make money. It's of no benefit if you don't have the disease. | 27 | 21 |
ELI5 Top-level government direct exchange is often said to proceed via a 'secure line' - how is such a line secured? | It varies of course but usually it involves something like end to end military grade encryption and only moving the call over infrastructure which is difficult for a listener to compromise, such as military communications satellites or secret fiber optics cables. There is no such thing as communication that is impossible to intercept and decode but it can be made impractically difficult. | 13 | 16 |
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If natural fruit juices contain large amounts of sugar, why do we only seem to refine sugars from a select few plants (sugarcane, sugar beets) instead of from fruits in general? | I understand that there's differences in the sugar composition (sucrose as a disaccharide vs glucose/fructose as monosaccharides, and that fruits contain more fructose), but I don't understand why "alternative" sugars like HFCS seem to be a relatively new thing, and limited to basically just corn so far as I'm aware.
In theory, humans have had access to fruit pretty much forever, so why do we only use a few dedicated sugar crops to produce refined sugar, instead of more regionally accessible fruits?
Is it simply a matter of economics, or is there some inherent difference that makes refining fruit sugars impossible? | Cost and consistency. You know exactly what compounds need to be removed from beets or cane every time to produce the same sugar. Strawberries or apples will not yield the same product through the same process (flavours, non-sugar compounds, inconsistent seeds/pulp), and both have (IIRC) lower - and more inconsistent - sugar content than both beets and cane. | 83 | 200 |
Is there a language-agnostic way to learn how to write multi-threaded programs? | Is there a language-agnostic way to learn how to write multi-threaded programs?
That is, without consulting each language, library etc. separately? | Not really, but there are only a few different ways to do concurrency, so a lot of your knowledge transfers:
- The threads/locks/semaphores model.
- The actor model.
- Promises/futures/tasks model. | 18 | 18 |
ELIF: What is the difference between Sunni's and Shiites | Sunni and Shia are two denominations of Islam. They split up from each other a long time ago because they disagreed on who should lead Islam when the founder, Muhammad, died. Because of this they have different religious leaders, writings, and philosophies. | 42 | 50 |
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ELI5: Why does stress tend to decrease performance at complex tasks? | I speed solve Rubik's cubes as a hobby, and I've noticed that my solve times are consistently worse when I'm feeling anxious about my performance than when I'm relaxed and in the moment. However, I've heard stress and anxiety described as a response by the nervous system meant to heighten an organism's performance in high-stakes situations. Why would stress cause me to perform worse at this task instead of better? | The stress response evolved to improve our performance at a very specific set of tasks: fighting or running for our lives. So things like energy, blood flow, and stuff like that improve. But some things also get worse at the same time: notably for your example, rational thinking and fine motor skills.
It's possible, with experience and practice, to reduce the bad parts. | 41 | 51 |
CMV: The upcoming presidential debates should have questions that measure cognitive capability and knowledge of the US government as well as the world economy/geography. | During the debates they should ask both candidates things like "What is the current federal debt" as well as a geography section where they are given a list of countries to point to (specifically countries with US military installations/deployments)
Even some SAT level math questions or reading comprehension/LSAT logic based questions could give a side by side comparison of the cognitive capabilities would be a completely unbiased way to compare them.
To be clear, I'm not advocating people vote solely based off intelligence/cognitive capability, but I would imagine it would be a factor in the decision making process, and in the day of fake news and claims like "I took a cognitive test and it was the highest score ever" it would be interesting to have a true side by side comparison of the candidates. | A few counterpoints for you to consider:
1) The candidates' ability to articulate their stances on the issues, reasons for those stances, and intelligently address counterpoints already gives you evidence on their cognitive abilities,
2) Biden and Trump have very different approaches to governance, which impacts how important their cognitive ability is. Spending time on this during a debate implies that it's equally important for both candidates, which would be misleading.
3) It incentivizes "gotcha" questions that aren't relevant to actual policy or performance, and whichever candidate has better connections to the network hosting the debate will likely have a leg up on answering them. | 170 | 771 |
Why do tightrope walkers carry a long beam? | In addition to what has been said before, the beam significantly increases the walkers rotational inertia around the rope axis. So the same small imbalance in center of mass causes much less acceleration with the beam in hand. The walker has to react much less quickly to correct his position. | 16 | 19 |
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ELI5: What is the difference between Chaos Theory and The Butterfly Effect? | I thought I knew what The Butterfly Effect was, then someone (well, Life is Strange did) explained Chaos Theory, and they sound like pretty much the same thing? What is the difference? | Chaos Theory describes the circumstances in which something like the Butterfly Effect can take place. Chaos Theory is (among other things) a set of highly sensitive conditions which allow the Butterfly Effect (the precipitating dramatic effect of a small change on a sensitive system) to occur.
Chaos Theory is the line of dominoes. Butterfly Effect is you tipping over the first one. | 87 | 77 |
[General] Why do high tier civilization eventually regress? | So something I've always wondered is why do some stories for example in Man of Steel and many others where highly advance civilization with the ability to do things like bend space, terraform or even harvest stars for energy.
Why would they all of sudden decide to regress into an era where things are stagnant where research and science while have evolved aren't taking risk like they were before their days. It just doesn't seem plausible because the rational thing to do is to keep progressing and advance their technology but in many cases there's always an era where things go south and they start to abandon those ideals. | Advancement is to achieve a period of time where work is no longer necessary, and the civilisation can pursue their true dreams (be it expansion, leasure, culture, etc).
Take the Eldar of 40K, they began to basically explore every sin to find the greatest pleasure imaginable. They forgot to keep pushing themselves and then their arrogance caused a huge problem they couldn't fix.
The Asgard of SG1, wanted to play peacekeepers and forgot to check the dangers of cloning.
Any more examples readers can push forward? | 25 | 19 |
ELI5: Have relationships between organisms that had been established before molecular biology been confirmed with genetics? | If I’m not mistaken, a lot of the relationships between different organisms (tree of life) were first established in the 19th century and were done so by looking at similarities in form and function and is the basis for scientific names. Since the development of genetic analysis, has there been an effort to go back and confirm that these educated guesses were correct? If so, were there any huge surprises? Like learning that animals that were thought to be closely related based on how they look are actually much more distant | Yes. Modern taxonomy is mostly based on molecular biology and genetic similarity, not form and function, and has indeed revealed that many of the original groups weren't descendants of common ancestors after all. Of course, form isn't a *complete* coincidence, so a lot of this took the form of small adjustments moreso than totally remaking the taxonomy.
Probably the biggest exception to this rule is birds not being relatives of dinosaurs as originally thought, but just being, well, dinosaurs. | 20 | 34 |
What new philosophical ideas have emerged in the last 50 years? | Amidst the noise of the internet, social media, technology, it's easy to think we live in unprecedented times. And of course we do, but I'm wondering if there are any breakthroughs in the realm of ideas... along the lines of say Descartes or Kant?
Of course philosophy has splintered into a multitude of disciplines since those days, and some of those breakthroughs might now be considered sociological or psychological etc.
What's considered philosophically revolutionary from the last 50 or so years? | Kripke is probably the living philosopher who is closest to "Kant" status, Naming and Necessity was revolutionary, his reading of Wittgenstein reinvigorated the field and so on. David Lewis is also up there, his modal realism and counterpart theory has left an indelible mark on the field. The two of them dominate any discussion of modal notions, possible worlds and so on.
Otherwise Rawls' entire theory of justice. Likewise the topic is unrecognizable from what it was 50 years ago largely because of his work and the reactions (Nozick, Dworkin, Cohen etc.) it inspired. | 26 | 47 |
ELI5: How does Googles new AI work? | It is called machine learning and is quite complex.
What it boils down to is that you break a problem into discreet parts, or steps.
You show the machine all the different steps it can do. Then you tell the machine what the desired "win" condition is.
It goes and compares all the different steps and series of steps to figure out the best way of getting to the win condition.
As these models get better and more generic, we can let the win condition be more vague and it has more freedom to learn how to get there.
It is entirely dependent upon structures called neural networks, which have an input layer, a hidden layer, and an output layer. The hidden layer is trained to give outputs to certain inputs.
For a board game training data might be all the moves of a bunch of games, and which player won. We don't actually know what the algorithm inside came up with, because we didn't tell it what to do.
It learned how to get to the "win" state by analyzing a bunch of data and coming up with its own pattern recognition to apply to new games.
| 63 | 178 |
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I don't think its a good idea to treat illnesses that are genetic because we are increasing their rate in the human population CMV | By treating people with heart problems are we not just allowing them to make more babies who will then have heart problems? I realize that as a doctor it is your obligation to treat the patient and it would be absolutely unacceptable to let them die on this premise, but in this situation it seems like the human population is becoming more and more ill. Natural selection is just going away.
I really need to get this cleared up because I am pre-med and I want to be 100% morally driven to help people. Not questioning if im actually helping the human population as a whole.
EDIT: I just want to clarify that I am not thinking of witholding medical care as a solution. I understand that is unacceptable. Its more that I want to feel like I am bettering the human race as being a doctor not allowing it to be sicker. | If we can (relatively) cheaply manage or cure a genetic disorder in a person, how can we deny them the chance at a better life (or even life, period) on the basis that their future descendants will suffer from the same affliction, which by all estimates will be as easy or easier to cure by the time they are born. And who knows? At the rate genetic therapy is progressing, perhaps within a generation or two, we'll be able to cure a child and their descendants of the disease once and for all.
And what if the disorder isn't even fatal (before reproductive age)? That takes the whole "descendants" issue out of the mix, because they're still likely to reproduce. Then, your choices are:
1. Cure/treat the disease so that the person can live a longer/fuller life. They may or may not reproduce.
2. Don't cure/treat the disease. The person lives with a lower quality-of-life. They may or may not reproduce. | 45 | 80 |
ELI5: How did the Vikings and other seafarers of yore manage to sail to specific locations (ports, beaches) when the compasses they had only indicated direction? | Compasses can indicate direction but not really the specific paths they would have to take to reach specific ports or beaches. So although those sailors would have known that they're going, say, a direction like SSW, how could they know that they're on the right path to hit the port or beach they wanted to get to? If their boats were to "drift" sideways, they'd still think they're going the right direction, but could end up hundreds of miles off target, right? | Most "seafarers of yore" overwhelmingly tried to keep within sight of a coastline whenever they could. In situations where this wasn't possible, they referred to the stars, ocean currents, and (when available) compasses. Vikings were pretty good at this, Polynesians were *great*.
It is hard to overstate just how important the invention of reliable timekeeping was to navigation. Once you know the math, you can reckon your latitude pretty easily from the sun and stars, but calculating longitude without time or landmarks is **really hard**.
Shortly before naval chronometers really took off, one competing plan was to set up beacon stations which set off fireworks, every hour, **across the entire ocean**. Fortunately (unfortunately?), this plan was never implemented. | 33 | 29 |
[Star Wars] Why is technology so advanced, yet so seemingly outdated? | Unequal distribution of technology and resources. Xenophobia and limitations due to biological differences in adapting technology. Prolonged periods of technological regression from war and calamities. | 62 | 59 |
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How can a radiating body be in equilibrium with its environment? | The [Black Body Radiation article on Wikipedia](https://en.wikipedia.org/wiki/Black-body_radiation) says:
"Black-body radiation is the thermal electromagnetic **radiation** within or surrounding a body in **thermodynamic equilibrium** with its environment, emitted by a black body (an idealized opaque, non-reflective body)."
If equilibrium means there is no net transfer or matter or energy, how does a black body radiate anything?
The article also describes how the spectra of lava, fire and heated steel can be used to approximate their temperatures. All these seem to have a net transfer of energy into their surroundings, heating the air around them. | There’s two questions: How can a radiating body be in equilibrium, and how can we use a temperature to describe systems which clearly aren’t in thermal equilibrium.
1. If you imagine a body that’s in thermal contact with another, but no heat can conduct or convect between them, for the two bodies to be in thermal equilibrium means that they are absorbing and emitting heat via radiation at the same rate. So there’s no net heat transfer in either direction.
2. Strictly speaking, certain thermodynamic quantities like temperature are defined for systems at equilibrium, but all of the interesting things that happen in thermodynamics happen because you place two systems *not* in equilibrium in thermal/mechanical/diffusive contact with each other and allow them to try to reach equilibrium. The temperature, pressure, etc. are routinely used to describe systems *near* equilibrium, or trying to reach equilibrium with other systems.
If you measure the radiation spectrum of a red-hot piece of metal, even though it’s not in equilibrium with the air around it, you’ll find that the spectrum it emits looks like a Planck spectrum, and you can fit a temperature to it. | 30 | 72 |
CMV: Recycling should be easier. | With the current recycling there are 6 types of recycling: Glass recycling, paper recycling, metal recycling, plastic and textile recycling and finally electronic recycling. With each having its own sub categories: most noteably plastic: with 7 sub types of plastic.
With there being at least 13 types of recycling, the current methods of recycling are broken due to the public not understanding the intricacies of the system. Also, with no direct recycling options most people know that they can recycle metals leading to recycling bins having non-recyclable materials simply because the system is complex.
In my option, and please change my view, having machines that can directly recycle a few things like pop bottles, or prescription bottles, we can simplify the process and lead to more and better recycling. Please change my view. | It's not that you "make it less complex" you rather decide where you're going to handle the complexity. For example do you handle it at the individual level where you teach people through idk PSA or other public campaigns how to recycle stuff or do you force companies or government agencies to provide centralized facilities that sort out stuff into the different categories, each has it's own pros and cons. | 15 | 60 |
Why is water tasteless? | Sometimes you can taste the minerals in it, but in general it is tasteless. Why is this? Is it really tasteless, or have humans over thousands of years adapted to its real taste? | Water / H2O is an integral part in cells and is therefore always present around the proteins on the surface of olfactory / "smell detecting" cells. Such a system would nearly always fire and apparently a system which could offset this by detecting the *change* of water-smelling over time hasn't evolved anywhere. | 38 | 35 |
Economists: Is wealth a finite resource? | I have no training in economics outside of Micro/Macro 100 level classes I took 15 years ago. But I've been pondering this for a while and I'm sure there is an answer (or two).
Here's what I'm thinking, tell me where I'm wrong:
* money is essentially a representation of work.
* There are a finite amount of people to do said work.
* if we want to raise the standing of the poor, more affluent people must necessarily be less affluent, or productivity must increase accordingly.
I've been mulling this over in the context of the US presidential election and wanted to get my ideas checked. Is this correct or can we just "Grow the economy" and have everyone do better?
Thanks. | Well, let's start with the easy stuff.
1. In 1800, everyone was poor.
2. Now, in 2012, about a billion people are extremely rich, five billion are in economies that are growing, and one billion are still around 1800 levels.
Clearly, something happened. If wealth were strictly finite, then there's no way we could have gotten here from there.
Incomes rise over time, due to the accumulation of knowledge, capital, technology, innovation, and education. Economies grow over time due to the accumulation of knowledge. "Wealth" is only as finite as our engineers make it to be. | 20 | 17 |
CMV: Not everyone could/should go to university | There’s a big movement, especially among more left leaning liberals that higher education should be free and/or is a right. While it’s not doubt true that Education is an incredible tool for social mobility (and what I believe is the key for POC to rise up in this country), it is not feasible for everyone to go to university.
There is already a shortage of jobs in many majors. Particularly in the liberal arts, arts, and even some considered useful majors are struggling. If everyone is encouraged to go to college, and major in what they want to study, there will be an influx of educated people who do not use their degree at all. This is already the case, there are lots of women who go to college and end up becoming housewives. While it is their choice to make, when they state gets involved with paying tuition, I am pretty concerned with which majors are chosen.
Along the same vein, every person going into Computer Science is not feasible either. One of the greatest issues of our time is that the new industries that are creating the most new wealth (tech) are not employing that many people. It would be absurd to tell all the truck drivers to go “learn to code”.
At the end of the day, working class jobs will always be necessary. It depends on the industry, but many jobs will take a while to being automated. And young kids learning trades like becoming an electrician or plumber are very respectable careers.
Lastly, I look at the history of colleges, and what colleges provide, and realize that this is not an experience that everyone needs to have. College is almost utopian, it’s an intellectual safe space that pays for the free gym, free pool, pays for expensive and absurdly large instruments for the marching band, and pays for the debate team to fly across the country. Colleges used to be exclusive to the rich and über wealthy, so this level of funding and utopian luxuries make sense. But it’s far removed from reality, and is not necessary for all regular people to experience, and certainly not one that government should pay for.
CMV reddit friends. | Regarding the first point, there's a pretty important distinction between "higher education should be free", and "higher education is a right". Namely, the first doesn't necessarily entail trying to get *everyone* in.
Universities still have a limited number of spots. You can only cram so many people into a lecture hall before it becomes a safety hazard. An admissions process could still exist, and weed out people who aren't cut out for certain programs. | 19 | 63 |
What's more effective at reflecting heat, a sheet of aluminum that is polished or a sheet of aluminum painted white? | I've been wondering if something that was polished to a mirror finish was better at not absorbing heat through light than something painted with pure white paint. Any responses are appreciated! | It very likely depends on the details of your paint and of the light that you want to reflect. Something you see as "white" is going to be broadly reflective of all visible wavelengths, but it may absorb some of the IR or UV spectrum. If the incoming light has significant intensities of those non-visible wavelengths in it (like sunlight does), you may still absorb a lot of energy. Some white paints will likely do a better job at reflecting those than others, and you probably can't see the difference. The mirror finish will probably have similar limitations, as it won't reflect all wavelengths equally. Different methods of polishing might give different results for different wavelengths.
If this is for a practical use, not just a thought experiment, you probably also need to think about other factors, like how the finish holds up to wear. If the brightest, most-reflective finish only lasts for a short time in your target environment before needing to be touched up, it may not be as good for your purpose as a less reflective option that is more durable. | 14 | 19 |
[DC/Marvel] What is Magic exactly in each universe, and who are its top users? | Is it divine (Gods and stuff), is it some sort of natural energy, is it something beyond comprehension?
Who are the big names in each universe who use magic, what type of magic do they use? Can anyone use magic in these universes or is it a natural-born gift? | Magic in the Marvel multiverse is a discrete type of energy. It's the energy that is generated by the will of sentient creatures, and is empowered to alter the fabric of reality.
Magic in and of itself is natural, as in it is a regular and normal part of the structure of the multiverse. There are lots of subtypes and specializations of magic, as well.
An important but powerful subtype of magic is divine magic, which is manifested in and passed down by divine entities, or gods. It's hallmark is that it is generated primarily by belief- the will of sentient creatures dedicated primarily to the edification and service of the deity. Much of Earth's history has been influenced by divine magic.
In the Marvel Universe, there's different levels of reality, and magic has sway over almost all of them. Very few humans can access much more than the very lowest levels and are unaware or unable to interact with any of the higher realities and possibilities without assistance.
For the most part, the true nature of magic is beyond comprehension though. This is why most systems of using magic are concerned with distilling it into spells or locking it into artifacts or objects, and finding other ways of codifying and limiting access to it so that normal minds can unlock its potential.
Of those that can, the greatest is the Sorcerer Supreme, primary guardian and wielder of magic in the 616 universe, Stephen Strange.
Even he mostly uses spells and artifacts to access magic, so his power lies not so much in his pure ability, but in his breadth of knowledge of such spells and his proficiency in use of the artifacts he has access to, and the staggering number of artifacts he possesses.
There are some entities who are even more proficient in using pure magic, or are even composed of pure magic.
For example, Dormammu is an entity who hails from an entire magical dimension, one of several creatures of that type called the Faltine- composed completely of magical power. He has access to all kinds and types of magic, but mostly simply uses pure magical energy to accomplish his goals.
The Vishanti and the Octessence are groups of extra-dimensional magical beings as well, and also use the entire spectrum of magic. They also are the primary sources of the power the Sorcerer Supreme uses to protect the 616 main Marvel universe.
The gods and deities that use divine magic have some of the most powerful realms in existence. Odin, for example, has power sufficient to stand with some of the most powerful forces in the Marvel multiverse.
There are many entities who are powered by the emotional energy of sentient beings other than belief, as well. Those are called devils and demons, and they reside in realms that consist of that negative magical energy. There you will find Mephisto, Belasco, and such.
Hyper-dimensional creatures like 'the Old Ones' wield a sort of magic that is literally incomprehensible- it does not match with the ability of creatures in the 616 reality to perceive. Shuma-Gorath is a power in that fold.
You asked who can use magic in the Marvel universe. For humans and most humanoid aliens, the ability to use pure undistilled magic in the Marvel universe is usually an in-born trait. It can be manifested in humans through the Celestial gene that gives creatures superpowers, through the X-gene that powers mutants, or can be a hereditary gift passed down through the descendants of magical entities who bred with mundane creatures.
Manifesting the spontaneous ability to use magic was much more common on Earth in earlier eons when magic was much more prolific and unhampered by the logical belief of science. In the modern age, it's almost unheard of for a human to be able to wield magic unprompted by outside forces.
The three most common ways that humans do get access to magical abilities is to have them given to them by a high-level benefactor, to somehow get access to a magical artifact, or to be educated in the craft of using magic by a mentor.
| 37 | 37 |
ELI5: How does my body know if my vision is in focus or not? What tells my eyes to adjust? | Your brain knows from experience what things should look like and what things look like when they're out of focus. When you see something that your brain thinks looks out of focus, it controls muscles in your eye to change the shape of the lens on the front of your eye until they appear correctly.
This is why when you see a picture that is slightly out of focus, it makes your eyes feel funny -- because your brain keeps trying to focus on something that can't be focused on.
This is all done subconsciously like hearing, breathing, etc., so you don't have to think about it. Vision is controlled by the Occipital Lobe and Visual Cortex parts of the brain. | 13 | 15 |
Subsets and Splits