Wikipedia:Reference desk/Archives/Science/2012 November 4

= November 4 =

Syria Rebels
I came across this YouTube video in which the Syrian rebels successfully attack and capture an army outpost, I am confused how they managed to do this because in similar situations in which the US and its allies  encounter almost  daily in  Afghanistan, insurgents will try to attack army bases and the army will call in attack helicopters, which turn on their infrared cameras and can easily see the insurgents even in the day time and kill them with their 30 mm machine gun, or Rockets, Syria has some fairly advanced attack helicopters from Russia. I don't see why they can't do the same. Here is the video:

http://www.youtube.com/watch?v=IC8ENtjVp3I

--Wrk678 (talk) 00:03, 4 November 2012 (UTC)


 * Not really a science question, but there are several possibilities:


 * 1) Attack is too rapid to allow such a response. Air responses take time, and the base must be able to hold out until then.


 * 2) Communications are jammed or cut, so they can't call for air support.


 * 3) Syrian outposts aren't designed to withstand attacks from all sides. Many outposts are designed just to defend against one type of attack.  For example, posts on the border may be set up only to defend against cross-border attacks.


 * 4) The Syrian air force is simply overwhelmed, and can't respond as quickly as is needed. Lack of spare parts and maintenance issues from constant use can have such an effect.


 * 5) Multiple coordinated attacks stretch the Syrian air force too thin to respond.


 * Also note that often those bases are retaken by the Syrian military. In many cases, the rebels don't even attempt to hold them, they just raid them and then scatter. StuRat (talk) 00:29, 4 November 2012 (UTC)

Well, it looks like the attack lasts several hours, starting during the day and ending at dusk. Syria is a pretty small country so I think they could get their in time. I doubt the rebels have any kind of sophisticated jamming equipment that could jam military radios.--Wrk678 (talk) 09:35, 4 November 2012 (UTC)


 * Your premise that attacks on military posts in Afghanistan are always quickly suppressed by air attack may not be the whole truth. See 8 U.S. troops killed in Afghanistan, Militant attacks on two remote outposts also leave as many as half a dozen Afghan troops dead.; "It was precisely the kind of attack the top U.S. commander in Afghanistan is hoping to stave off by recently ordering troops to withdraw from such small outposts...". Also the Battle of Wanat and Siege of Sangin. None of these attacks were ultimately successful, but it was sometimes a "damned near-run thing"; although as yiou say, air power was used in a suppressive role in all cases, it's often hard fighting on the ground that wins the day. The training and equipment of the Syrian Army may well not be up to the standard of professional NATO troops. Alansplodge (talk) 10:07, 4 November 2012 (UTC)


 * Doing a quick search I find "In recent days it has appeared that Syrian rebels have acquired heavy weapons that have forced the government's air force to bomb rebel-held zones from higher altitude, leading to claims of more indiscriminate bombing."  The video shows a helicopter spiraling down and exploding in a ball of fire. Wnt (talk) 13:32, 4 November 2012 (UTC)


 * This outpost was a minor one possibly. I doubt they send even one aircraft to all fighting that is taking place. The Syrian_Air_Force. What's the point of risking a crown jewel like an attack helicopter to save just half a dozen of trapped soldiers? Comploose (talk) 19:42, 4 November 2012 (UTC)

Well in Afghanistan fighting on the ground can stave off the assault but it's usually when the attack helicopters come  that the insurgents will retreat. Usually there is a "Alamo" call that is given when the base is starting to become overrun that brings all airborne helicopters to the area.

Even though this was a small army base its capture involved the capture and probably the execution of several dozen or more Syrian army soldiers, so I would think the government would prioritize that and send attack helicopters over there. If you watch the end of the video after they capture the base, They hang around there for at least several hours afterwards and nobody shows up, if, for example, it was a priority issue, they probably would have shown up  "late" a  hour or so after the attack, which they did not.

The thing is I have watched numerous videos of these Syrian rebel attacks, many of them last for hours or more and it doesn't appear that any Syrian attack helicopters usually show up. This makes me wonder if in fact the attack helicopters the Syrians use do in fact have infrared cameras in them. Does anyone have any information on this? --Wrk678 (talk) 21:28, 4 November 2012 (UTC)
 * Attack helicopters are not an "I win" button, same as tanks. A chopper or a tank will rarely be sent to enter an engagement with no support. To be effective there has to be a co-ordinated attack. All it takes is one enemy soldier with a cold war era anti-air or a anti-tank weapon to be a serious threat to several million dollars worth of military hardware. With no ground support or good reconnaissance, sending a lone chopper might just be too risky. As is noted above, at least one chopper has already been lost and if I'm not mistaken there's been a few. Vespine (talk) 22:11, 4 November 2012 (UTC)

Well, it's pretty standard procedure to send attack helicopters to bases being attacked, regardless of anti-air weapons. They had those in Libya and Afghanistan too.--Wrk678 (talk) 22:55, 4 November 2012 (UTC)
 * That's an assumption on your part. I see no reason to believe it's "standard procedure". You don't know all the details, as I said, in the other circumstances, maybe there was ground support or reconnaissance available nearby, maybe the threat of anti-air was lower, maybe the pilots were more highly trained; there's just way too many factors involved to say something like "it's standard procedure". Warfare strategy is a very complex topic, it's not just a list of "standard procedures". Vespine (talk) 01:34, 5 November 2012 (UTC)

I disagree with that, military tactics are fairly universal. --Wrk678 (talk) 01:37, 5 November 2012 (UTC)
 * Well, this very scenario seems to disagree with your evaluation. There was a reason why they didn't send attack choppers, I suggested a few explanations, i'm not sure what other answer you would find more satisfactory. Short of asking the "people in charge", which no doubt would not tell you anyway.. I'm not saying that there aren't universal rules of engagement, I was trying to show that there would be lots of exceptions and finer details which civilains would not be privy to. Vespine (talk) 02:34, 5 November 2012 (UTC)

Well, I'm starting to suspect their helicopters are not equipped with infrared cameras, in which case they wouldn't be of much use in that scenario. If you read about the http://en.wikipedia.org/wiki/Battle_of_Kamdesh  it talks about how the solders basically gave up and air support was the only thing that saved them. --Wrk678 (talk) 05:47, 5 November 2012 (UTC)

Oxidative stress and immune system
Hi all,

Can someone tell me in which treatise (hopefully up-to-date) can I find something about general relationships between the oxidative stress and the cells of the immune system? Thank you very much!

151.71.165.245 (talk) 10:12, 4 November 2012 (UTC)


 * This is a very general question, almost too general to answer. (Do you mean the effect of oxidative stress on invading cells, for example, and what level of review do you want?)  Get to know http://www.ncbi.nlm.nih.gov/pubmed for making general queries and narrowing them down; http://scholar.google.com has become a very serious alternative.  Leaf through oxidative stress, phagocytes including neutrophil, monocyte, and macrophage, phagocytosis, myeloperoxidase, reactive oxygen species, hydrogen peroxide, hypochlorite... it's no small topic, yet one key idea is very straightforward: the immune system recognizes invaders and puts them in special bins where they are bleached to death (and otherwise digested). Wnt (talk) 13:25, 4 November 2012 (UTC)

Thank you very much. My problem is exactly that I need a general approach to the topic, while the majority of papers I met on-line (including those found using the external links you seggested) is very specific. For this reason I was looking for a treatise. If you are so kind to seggest me a book about the immune system that covers the subject, it will be great!

Many thanks.

193.205.224.192 (talk) 12:54, 5 November 2012 (UTC)

Black holes at the speed of light
Hi, I have a sort of simple question. If you were to accelerate into a black hole would you travel at the speed of light as you cross the event horizon?

Or if you accelerated in at an angle, so your horizontal component of velocity would be say 100mph and your vertical component would be the increasing velocity due to the acceleration due to gravity of the black hole, could you even hit the speed of light before you hit the event horizon?

(This is assuming you have infinite fuel and are not crushed by the G-force and gravity) — Preceding unsigned comment added by 31.54.166.196 (talk) 14:51, 4 November 2012 (UTC)
 * From special relativity no particle with a rest mass can travel at the speed of light. So in answer to your question no you would not be travelling at the speed of light when you cross the event horizon.Dja1979 (talk) 15:58, 4 November 2012 (UTC)

What would your speed be as you crossed the event horizon? — Preceding unsigned comment added by 86.146.165.159 (talk) 16:17, 4 November 2012 (UTC)


 * For an outside observer your speed would be (surprisingly) equal to zero because of gravitational time dilation. Dauto (talk) 16:30, 4 November 2012 (UTC)
 * For this reason, it has been argued that black holes (as seen from outside) can never truly exist because they take forever to form! —Tamfang (talk) 20:12, 4 November 2012 (UTC)


 * In fact, any observer crossing the event horizon will travel exactly with the speed of light as measured in his own time. Ruslik_ Zero 19:13, 4 November 2012 (UTC)
 * Is this so? From special relativity, we know that any thing in the universe, that has a rest mass, cannot travel at the speed of light. Thinking about it more, maybe the event horizon is outside the universe (i.e. it doesn't interact with the rest of the universe, it is inside the black hole), so special relativity doesn't hold.Dja1979 (talk) 20:27, 4 November 2012 (UTC)

So you would travel at the speed of light then? Also how long would it appear to the outside observer that you freeze for? — Preceding unsigned comment added by 86.146.167.230 (talk) 20:08, 4 November 2012 (UTC)
 * If an observer sees you freeze, then you never actually make it over in their reference frame, so the answer is forever. However the observation will be redshifted to extreme levels as well, with lower energy photons, and less of them, so eventually nothing will be observed. Graeme Bartlett (talk) 20:15, 4 November 2012 (UTC)
 * This has nothing to do with reference frames. No one outside the black hole will ever see you inside because light from inside can't reach the outside. It doesn't matter what speed they're going. -- BenRG (talk) 17:53, 5 November 2012 (UTC)

As time speeds up relative to how fast you are travelling, does time stop for the person at the event horizon travelling at the speed of light? — Preceding unsigned comment added by 86.146.167.230 (talk) 20:23, 4 November 2012 (UTC)


 * Black hole says
 * According to his own clock, [an observer falling into a black hole] crosses the event horizon after a finite time, although he is unable to determine exactly when he crosses it, as it is impossible to determine the location of the event horizon from local observations.
 * But Event horizon says
 * An observer crossing a black hole event horizon can calculate the moment they have crossed it, but will not actually see or feel anything special happen at that moment.
 * "Unable to determine exactly when he crosses it" versus "can calculate the moment they have crossed it" is contradictory. Does anyone know which is right?
 * A related question: According to those articles someone inside the event horizon can see someone else who previously entered on the same path. Does the previous entrant appear to accelerate to infinite velocity or decelerate to zero velocity? Duoduoduo (talk) 23:49, 4 November 2012 (UTC)
 * The point is that the observer is unable to determine the location of the horizon with a local experiment but can calculate it's location if he has full knowledge of the black hole's mass, location, etc. For instance, we could at this very moment be crossing the horizon of a black hole so large that it's center is outside of the observable universe and therefore unknowable. There is no experimental test that we could use to find out whether that's true or not. BTW the guy falling in the black hole is not moving at the speed of light for any local observer as stated above by some people. That's just wrong. Dauto (talk) 00:01, 5 November 2012 (UTC)
 * Let's start with the basics. You have a gravity well, and the speed you gain when falling in is the speed you lose when falling out.  If you fall into a black hole from a long way away, just barely miss the event horizon somehow and come back out, you should come to a stop at the same long distance away (ignoring gravity waves and such means by which you might lose energy!).  Because only something travelling at nearly the speed of light can do this, the speed you must reach near the event horizon is almost the speed of light - relative to the outside observer.  But of course, you're falling, so you're at rest the whole time as you see it.  If you sped up on the way in though, that doesn't mean you'd be going faster than the speed of light relative to the outside - you'd just have more kinetic energy which, ultimately, would take you flying away from the hole at high speed when you got out.  But since mass can acquire an arbitrarily large amount of kinetic energy by going just a little closer to the speed of light, you'd still be below that speed.  Ultimately, the outside can only see you where you'd going slower than light relative to their frame of reference; after that, they see... an event horizon. Which is defined as a spot where the math breaks down - you don't really have infinite mass, they can't see you have infinite mass or that you're going at the speed of light, and they're unlikely to get your account about what you saw, though the whole time... you're still at rest. Wnt (talk) 15:10, 5 November 2012 (UTC)


 * The math doesn't break down at the event horizon. You can draw an event horizon anywhere in spacetime:

_______________       |         /     |   ^        | inside /      |   |time |      /       |   |        |      / outside|   | |_____/_________|   > space


 * If the diagonal line is moving right at the speed of light, it will "behave" just like a black hole event horizon. The inside region "attracts" objects from the outside: you will fall through unless you accelerate away, and the closer you are the larger the necessary acceleration. Nothing from the inside region can ever reach the outside, even light. If someone crosses from the outside to the inside, anyone who remains outside will never see them cross (they'll never see the light, that is). They will see the moment of crossing redshifted into the indefinite future. These makeshift event horizons even emit particles (Unruh radiation), just like black hole event horizons. You are falling through event horizons all the time. -- BenRG (talk) 17:53, 5 November 2012 (UTC)


 * Hey BenRG, I like your diagram. It really brings home to a lay person how trivial the concept of a horizon really is. Dauto (talk) 21:47, 5 November 2012 (UTC)

So why is the nootropic market kind of small?
Why are students not tested for doping? Is there any genius known for taking nootropics. I know that the mathematician Erdos was known for taking amphetamines, and some artists do not hide their past consume of drugs (although art is an entirely different field, you can fuck up with your brain and still be among the best in the field). Comploose (talk) 20:04, 4 November 2012 (UTC)


 * At the moment, there are no prohibitions against taking "cognitive enhancers", even for standardized testing. If there are no prohibitions, there is no testing. If, at some point, the use of these is banned — a big if, as it is a complicated issue of performance, mental health, doctor's recommendations, and so on — then presumably testing will have to become part of any effective enforcement regime. --Mr.98 (talk) 20:47, 4 November 2012 (UTC)
 * Mathematicians and artists do not really compete with each other as directly as people do in sports, that's why I think perhaps our society doesn't see cognitive enhancement in as bad a light as physical enhancement. Whatever competition there is amongst artists and scientists, it's not the "ends" of those pursuits. Sure you compete indirectly, but you compete indirectly by being born. In competitive sport on the other hand, winning against your opponents IS why you play the sport in the 1st place. I suppose students at one stage will compete for university places and scholarships, but you don't get professional "test takers" who make a living just by taking tests. Vespine (talk) 22:00, 4 November 2012 (UTC)
 * Nootropics are generally debatable. Why would there be a way for a drug to improve on intelligence, that nature doesn't already take advantage of?  I suppose that if they increased calorie expenditures or something it would be conceivable ... still, what we see are more often things like modafinil.  Tell me ... if much of sleep can be conveniently avoided with a little pill, why does every animal species from fruit flies to man go through the process, despite obvious vulnerability to predation and decreased opportunity for food gathering? Wnt (talk) 22:06, 4 November 2012 (UTC)
 * Isn't that appealing to nature? The same argument could be made against the bifocals that I'm wearing right now: "Why would there be a way to compensate for myopia, that nature doesn't already take advantage of?". I concur with your overall stance, I just think a different argument would be more convincing.A8875 (talk) 22:34, 4 November 2012 (UTC)
 * When we are awake we are on natural stimulants. The reason why animals sleep is due to competetion. If you have some machine that has to repair itself that is performing at some level, then you can put it on stimulants and let it perform better at the expense of its repair capacity. So you need to balance that by having a downtime for repair. Also, performing repairs in downtime is more efficient. Count Iblis (talk) 23:02, 4 November 2012 (UTC)
 * I see this less as appealing to nature as appealing to evolution. Evolution, however, is notably poorly tuned for ages that people rarely reached in primitive times, or for activities like reading that were not important many millennia ago, hence the bifocals. Wnt (talk) 01:27, 5 November 2012 (UTC)
 * The analogous argument could be made about studying: "Evolution is poorly tuned for activities like memorizing large amounts of information.".A8875 (talk) 03:21, 5 November 2012 (UTC)
 * Well, that's a valid point. The idea of general intelligence is a peculiar one, central to understanding humanity, and utterly mysterious.  Why did humans evolve so many different skills that everyone has - why aren't there genotypes, families or even races that don't understand how to work calculus, but can do everything else just fine?  But we digress... Wnt (talk) 15:34, 5 November 2012 (UTC)


 * (after ec) Add to this that the enhancing effect of drugs, any drugs, is rather dubious. That's no drug that will make you wiser. Some will make you kind of restless, reduce your fatigue, keep you awake and so on. But, in my personal experience, people who use them are the kind who need to spend the night awake before exams or people who have mental problems and need to function normally. These groups are not really skewing things to their benefit. OsmanRF34 (talk) 22:12, 4 November 2012 (UTC)


 * Ritalin lengthens attention span, and as any student knows, not being distracted while studying is the most important factor in doing well. Some of that is due to the placebo effect, but there's a statistically significant portion that isn't.  Testing students for doping is infeasible because students don't confine their studying to a single 1-minute competition every month or year; they study 6 days a week, for half of their waking lives.  --140.180.252.244 (talk) 00:14, 5 November 2012 (UTC)


 * Come to think of it, a main reason why nootropics are not yet popular is that there has been little effort to wage a "war" on them. (Unless you count methamphetamine, which has much in common with Ritalin, if that counts)  I think if we had a major DEA push to put people selling modafinil in jail for twenty years, the merchants with good police connections would make a huge profit, giving them a motive to hype it as a "hip" thing in the media and on the street; before long people would be coming up with super-potent addictive analogs to take by injection and we'd be hearing stories of people going without sleep for six months until their brains turn to tapioca.  After that a multibillion-dollar trade in it would never end. Wnt (talk) 01:27, 5 November 2012 (UTC)


 * I am not sure why you would conclude they are "not yet popular." Amongst those with money and incentive to do well academically, they are immensely popular. A ridiculous percentage of kids at any high-end private high school has prescriptions to them, and many others purchase them illegally from those who do. They are not recreationally very popular, but in terms of getting ahead at the junctures in life that make quite a lot of difference — standardized testing, getting into a "good" school, etc. — and are actually competitive (which is to say, zero-sum — there are winners and losers), there is a quiet little arms race going on. I do suspect that someday there will be some consensus about some standards here, about whether the ability to pay for concentration tilts the scale too much in favor of those with means, but we aren't there yet, just the early murmurs of ethical concern. The issue is a genuinely complicated one, ethically and medically speaking. --Mr.98 (talk) 13:20, 5 November 2012 (UTC)


 * The question is open to discussion from a medical standpoint, but I don't see that it skews the playing field towards privileged people. I don't believe many people are not able to pay for generic Ritalin. Filling a prescription through Walmart costs only $4/month, and maybe the poor at the bottom won't be able to buy this generic Ritalin, but most people would be able to afford it, if they want to.


 * Ritalin has the same problem as other nootropics. Although they might help you perform better if you are late for preparing yourself for one of the 'junctures', I do not believe it will make you any better long term regarding developing and using certain abilities like writing, knowledge acquisition, social abilities, creativity, planning. I am not trying to say that nature made us perfect the way we are, but Ritalin specifically, which works in a similar way to cocaine and amphetamine, has many drawbacks, and the effects on long term users are not well understood yet. It certainly makes you more awake for a certain time, but I believe this is probably at cost of your memory, health (mental and physical), and a rebound effect. I don't see the advantage here. It looks like a real arms race, when both sides invest lots of resources in things that they need, just because the other side have it. OsmanRF34 (talk) 14:53, 5 November 2012 (UTC)

Coffee and tobacco? μηδείς (talk) 02:24, 6 November 2012 (UTC)

engine diagram
Hi : Looking for a engine diagram and info.for a toyota avalon xl 2006. Thank You — Preceding unsigned comment added by Carol9905 (talk • contribs) 20:28, 4 November 2012 (UTC)


 * Your local library may have repair and service manuals for that car. Libraries often buy volumes that cover repair procedures for a manufacturer's entire line over 4 years or so. If it is a vehicle that you plan on self-servicing on a regular basis, you might want to look into buying the book made specifically for that car from an auto parts store. 209.131.76.183 (talk) 13:43, 5 November 2012 (UTC)


 * Also, have a look at this Google Image search and see if there's anything helpful there (not much of a mechanic myself). Alansplodge (talk) 16:24, 5 November 2012 (UTC)

Confusion about how telescopes work
I don't really get how a Newtonian telescope works.

Rays of light reflecting off the object we're attempting to view enter into the telescope tube effectively parallel because of its huge distance from us. The rays then reflect off of a parabolic mirror, which focuses all the rays to a point. At least it would, were it not for another mirror obliquely oriented, which reflects these rays to the telescope's eyepiece, which magnifies the image.

Here's my problem: if all the rays are focused to the same point after reflecting off the parabolic mirror, how can we distinguish between different points on the object? Wouldn't the image of the object just be a point? 65.92.7.202 (talk) 22:25, 4 November 2012 (UTC)


 * All parallel rays focus to the same point. Non-parallel rays do not.  If you imagine 100 rays travelling perpendicular to the mirror's axis, they focus at a certain point on the focal plane.  If you imagine 100 rays travelling at an angle of alpha to the perpendicular, those rays focus to a different point on the focal plane.  The distance between these 2 focal points is proportional to alpha.  --140.180.252.244 (talk) 00:04, 5 November 2012 (UTC)
 * Even your eyeball focuses light into a point, but unless there's something wrong with your eye, the point isn't on your retina. Maybe an image like this will help. I think a similar thing happens in the telescope. Vespine (talk) 05:06, 5 November 2012 (UTC)
 * Are you sure you don't have it backward? Unless there's something wrong with your eye, the image is on your retina.  If it's not, you either have myopia or hyperopia  --140.180.252.244 (talk) 07:52, 5 November 2012 (UTC)
 * Yes, the image is on the retina in a normal eye, but Vespine's point is that the focal plane lies between the lens and the retina. This whole thread arises from mistakenly assuming that the focal plane is the image plane. Gandalf61 (talk) 14:55, 5 November 2012 (UTC)
 * In a Newtonian telescope the focal plane is the image plane. The first answer by 140.180.252.244 is correct, and Vespine's followup isn't helpful as far as I can tell. -- BenRG (talk) 18:04, 5 November 2012 (UTC)


 * Ah, right — in astronomy the image plane "is" the focal plane because the objects viewed are "at infinity", unlike in most daily uses of the eyes. —Tamfang (talk) 19:57, 5 November 2012 (UTC)
 * Hang on, the focal point is different then the focal plane. The OP was talking about the focal point. You know, the spot where the light focuses to a point if you shine the sun through a magnifying glass. In a Newtonian telescope, that point doesn't fall on your retina. That's what I was trying to show with the image I linked. Vespine (talk) 21:37, 6 November 2012 (UTC)

Light slow motion
Is this real http://www.youtube.com/watch?v=SoHeWgLvlXI&feature=related. If it is I want to see the effects of relativity. I'm sick of hearing "oh yea relativity has been experimentally verified countless times" I want to see it with naked eyes. Why didn't they do that? Money is tight (talk) 22:42, 4 November 2012 (UTC)
 * I don't think that clip shows anything not explicable by classical electrodynamics; you see a light wave propagating, which is impressive, but not so much related to relativity. The easiest way to observe relativity with your eyes would probably be like they did it in 1919. You'd need to observe the stars around the sun (with a telescope ofc) during a total solar eclipse, and then compare the positions of the same stars with a picture you took at night when there was no eclipse. You should see the effect of the sun bending the light of the stars. - Lindert (talk) 23:13, 4 November 2012 (UTC)


 * The most dramatic visual demonstration of relativity is probably the Einstein ring. That article has lots of photos.  --140.180.252.244 (talk) 00:00, 5 November 2012 (UTC)


 * Einstein's prediction before the eclipse was not that gravity would bend light – that was predicted classically – but how much. An Einstein ring doesn't tell us anything about general relativity unless we know the mass of the galaxy in front — or does it? —Tamfang (talk) 00:10, 5 November 2012 (UTC)


 * They can get a source traveling at half the speed of light and emits light together with a source that stays still, I want to see these two light beam travel at the same speed. Money is tight (talk) 05:51, 5 November 2012 (UTC)


 * To accelerate a macroscopic object (a light source) to such speeds is impractical if feasible at all with our current technology. And where would you film such an event? The light source would leave earth sooner than you can blink your eyes. - Lindert (talk) 08:59, 5 November 2012 (UTC)
 * It takes around 0.155mc² to accelerate an object to half the speed of light (γ=1/√0.75), so around 3.32 kilotons of TNT for a 1g object. Given enough time and monetary resources, getting an undersized LED throwie to 0.5c should be right near the edge of humanity's current technological capabilities, but unless you have Scrooge McDuck-levels of wealth, it's just not going to happen. And even if you do happen to have that kind of wealth, you're going to need to pull some strings with the UN, because I doubt they'll think "because I don't believe in special relativity" is a good enough reason to allow you build what is essentially a weapon of mass destruction.-- Link (t&bull;c&bull;m) 15:22, 5 November 2012 (UTC)
 * Assuming your LED can survive 1,000,000 g acceleration, it will take around 15 seconds to accelerate it to 0.5c, during which time it will move about 1.5 million km. This is not within the capabilities of the human race now or in the foreseeable future. -- BenRG (talk) 17:32, 5 November 2012 (UTC)


 * Would you be satisfied with the Advanced Light Source, where the light is emitted by charged particles travelling at >99% of c, or the Large Hadron Collider, where collisions happen at such a rate (~1 billion per second) that they have to take careful account of the light-speed delay in order to correlate the results from different parts of the detectors?
 * Anyway, there's nothing strange about the speed of a wave being independent of its source. The same is true of sound waves, for example. -- BenRG (talk) 17:32, 5 November 2012 (UTC)

Yes the invariance of speed of light is very strange, because it predicts things like length contraction and time dilation. I just find it very difficult to believe and want to see it for myself. Money is tight (talk) 01:02, 6 November 2012 (UTC)


 * Unfortunately the speeds and energies involved are so incredibly high that there aren't many good ways to easily observe the effects directly. I recommend you look through Tests of general relativity and Tests of special relativity, and attempt to understand how some of the experiments worked and why the results confirm relativity. If there are tests with methods that you doubt or ones where you don't understand what the test is supposed to be doing, people here will be more than happy to help you work out the details. Some of the tests are pretty simple, but still very difficult to pull off on your own due to the precision required. 209.131.76.183 (talk) 15:32, 6 November 2012 (UTC)


 * The reason it's hard to see evidence of modern physics is that if it were easy it would have been noticed much sooner, and hence wouldn't be modern. -- BenRG (talk) 22:26, 6 November 2012 (UTC)