Another speed of light question?
964282
Well, since the only planet that we known absolutely, positively has green vegetation is the Earth, then all measurements of the speed of light here in the atmosphere are in the presence of green vegetation.\n\nAs far as any astronomical, deep space observations -- heck, we've only just detected Jovian-class planets in other solar systems.  No known vegetation there!\n\nSo, I'd have to say that the answer to your question is no, we've not made any observations of the type you describe.
11463
The changes propagate at the speed of light, so I guess the time taken is,\n\nt = r/c where c = speed of light
1061265
The most recent research that I've seen was shown on the TV program "Horizon" here a few years ago.  The research suggested that under certain conditions (somehow linked with Einstein's cosmological constant) the speed of light could possibly change.\n\nHowever, for the time being at least we can easily assume that the speed of light is a constant.  The last I heard was that the research they were doing on the speed of light has was inconclusive, so it may take a while longer before we really know if it can change or not.
647799
You can't go at the speed of light. It's a theorical limit, so it's unreacheable. Only the light can reach it.\n\nIf C is the speed of light, the fastest you can get is C*0.999999999... (insert as many '9' as you want). When you turn on the headlights, they will be somewhat faster: they'll reach the speed of light.
283556
The speed of light is a CONSTANT and has the symbol c in Science and is measured in meters per second.\n\nc (the speed of light) is equal to 3 times 10 to the power 9.\n\nNow 3x10*9 meters per second equals 3000000000 meters per second. (3 then nine zeroes!).\n\nc is important in physics because nothing can go faster than  c. \n\nNothing can go faster than the speed of light and as Einstein showed with the Theory of Relativity (a very important theory in physics) when an object (mass if you will) approaches c it gets bigger and bigger!! \n\nIf it gets to c then its mass will become infinite - this is impossible! An object with infinite mass! Hence it is impossible to reach the speed of light. \n\nHope this helps.
1103100
Here's the equation T = T' / sqrt[1- (v^2/c^2)]\n\nT is time measured by an observer at rest.  T' (read: T prime) is time measured by a moving observer.  v is the moving observer's velocity and c is the speed of light.\n\nThe speed of light is very fast.  So if v is 100 mph or 10 000 mph when you divide it by a number like c (186000 mps that's miles per second so a huge amount of miles per hour)  the v^2/c^2 value is zero and T = T'/sqrt (1) which is T = T'/1 so there is no measurable difference.  \n\nBut plug in 9/10 c for v.  That means an object going 9/10 the speed of light.  You get T = T' / sqrt[1-(9/10c)^2/c^2]\n\nc^2 cancels out and you get T = T'/[sqrt 1-(81/100)] T would be 2.2 times T'.  More time transpired for the non moving observer.\n\nHow did we get the equation?  Einstein was really smart.
855043
It's all theory, we don't know if (something) can exceed the speed of light. I would argue that time would be void at that moment, but again it's my theory. Interesting thought though.
412765
1m/s physically you are walking towards a stationary object that is reflecing your image, as such you are walking towards it at the steady 1m/s.\n\nIf not that then you are both approaching a common point at 1 m/s so you combine your velocities to get 2 m/s.  but that's semantic bullcrap\n\nYou could get really technical and add in the fact that the photons are travelling back at you at the speed of light but that's just stupid.
336972
Wow, great question(s)!  You're brooding over something called the 'twin's paradox', read more about it in the link below.  Basically, what you're fretting over are a couple of the (wierd) implications of special (and general) relativity.  You (and what some others have said) are right, all velocity is relative, which comes from the simple fact that there is no special place that we can call 'still' which we could measure our velocity against.  The single exception to this lies in the speed of light, which is constant for everyone everywhere, no matter what their speed is relative to anything else.  (Note: light isn't special, the only reason it's able to travel at the upper speed limit is because it's particles, photons, have no mass.  Nothing with mass can ever travel AT the speed of light, only near if it is pumped up with huge amounts of energy.)  Think about the wierd implications of this; even if you were able to travel at 99.999999% the speed of light, and your friend would also be able to travel the same speed in the opposite direction, if you shined a light back toward your friend and could measure the photon's speed as they travelled between you the photons would STILL be travelling at the speed of light.  Ok, what does that mean?  The speed of light is just a speed, like any other, but is a constant that can not be exceeded.  Well, like any other speed, c (the usual symbol for the speed of light) is definded as the ratio of the distance travelled (call it 'x') by the time it took to travel it (call it 't'), or c=x/t.  But if 'c' can't change (because it's a constant) what is changing?  There's only two other things in the equation, x (the distance, a measure of space) and t.  Time and space enter into Einstien's equations here, the only way to keep c constant is for x and t to somehow collaborate to change together to make it so.  This is why time (and space) are so 'relavent' to velocity.  And as a matter of fact, time is 'relavent' to gravity as well, as Einstein pointed out so much better than I can.  For Einstein, the breakthrough came when he realized that there is no measurable way to distinguish between gravity and acceleration (a.k.a. the rate of change of velocity with respect to TIME), or more importantly, between the lack of gravity (say a person floating in space) and a particle (or person) in a falling box, they're indistinguishable.  From these two simple ideas (the constancy of c, and the equivalence of gravity and acceleration) Einstein formulated the theory of general relativity, one of the crowning achievements of human thought.  You ask good questions, keep wondering!
410856
Engery\nMass\nc is the speed of light (why c? I don't know does anybody else?)
779931
The speed of light in a vacuum is exactly 299,792,458 meters per second (fixed by definition). Although some people speak of the "velocity of light", the word velocity is usually reserved for vector quantities, which have a direction.\n\n\nNothing has a speed greater than the speed of light.\n(except in Science Fiction stories)
160198
This is a very interesting question and most people don't understand it.\nTHE value of the speed of light  is "C" in vaccuum IRRESPECTIVE of the refernce frame. Light will travel at velocity C (relative to you) even if you are going at C. \n\nSounds crazy? This is at the fundamental of Einstien's assumption which was later proved right. Common sense is often wrong.
56541
You would be in a different universe than you are now, because the laws of our universe say that a massive object can't go faster than the speed of light (or even as fast).\n\nAlso, if you changed the question to "...1 mile per hour less than the speed of light", you would have to specify "relative to ..." (what?)  And then you would have to say, what would happen as observed by (whom?).  In this question, relative to you, the headlights would turn on and you would be able to see things 186,000 miles ahead of you (as you measure miles) within 1 second (as you measured seconds) .  Relative to the observer that thought you were moving 1 mile per hour less than the speed of light - assuming you were moving toward the observer - you would get to him or her just a tiny fraction of a second after he/she saw the headlights turned on.  Your measurement of the speed of light would be consistent, but your measurments of time and distance would be very different.
799784
In theory, yes.  Because the light particles that were traveling slower than you would have been slower.  Very good question.  However, speeding past the speed of light would mean the fundamentals of E = Mc^2, would cease to make sense.
506771
Actually by what Einstein explained, da light will still be in  front of da car, it won't go behind u no matter how fast u r going even if u r faster dan da speed of light. Weird? rit. I too thought so, It was explained in discovery channel. Well I'll try 2 explain it 2 u, But it wud hav been easier if I cud actually show it by som animations. When u r travellin at da speed of light, time stops. Ya it does. Time is somthin like per user setting, it is unique for u & each & every one. Think dat ur carrying an Einstein's clock, which is a simple devise with 2 mirrors facing each other with a photon bouncin of the mirror. Each time it bounces from a mirror u'll hear a tic sound, that will b 1 second for u. Say u travel at a speed little less dan light u r movin forward but da photon has 2 move a lot more distance than it initially had been, which was in a straight line, but now it's motion will b som what like a hypotenuse, so it has 2 travell more distance dependin on ur speed. So ur 1 sec will not be da same as 1 sec is for som 1 on earth. So actually ur headlight will be actually movin faster dan u no matter what
447950
1.  According to the Special Theory of Relativity you can't travel as fast as the speed of light.\n\n2.  The General Theory of Relativity has to do with gravity, not what happens when you approach the speed of light.\n\n3.  If you could travel at the speed of light, the light from the sun could not catch up with you, no more than a pulse of light can catch up with another pulse of light.  So, you couldn't see the sun again.
842139
No.\n\nIt seems like it ought to be different, doesn't it?  But the genius of Einstein's discovery was that the speed of light is a constant, and that it is the limiting speed of the universe.  Literally everything else--even time itself--will change in order to keep the speed of light constant (approximately 186,000 miles per second).  \n\nIt is a difficult concept to get your mind around, but it's been more than 90 years since Einstein did this work, and every experiment done since then has confirmed it.\n\nGood luck!!