If I'm travelling away from the sun at light speed, does General Relativity mean that I can still see it?
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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.
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Nothing can travel faster than light. Your question is a good one and it relies on a nuance of relativity. Einstein stated that nothing can travel THROUGH space faster than the speed of light. The universe recession speeds have nothing to do with moving through space. We observe the universe receeding because SPACE is expanding faster than the speed of light. It is like a balloon being inflated. Since space itself is not limited by the theory of relativity no contradiction occurs I hope that helped.\n\nTo the person who mentioned black holes, these do not in any way prove that einstein was wrong. Follow me here it may get confusing. Light travels through space at the speed of light. A black hole is an entity so massive that it infinitely warps spacetime. So as light is moving through space it comes to this infinitely deep hole. The light follows the contour of space into the black hole. And because of the extreme force and curvature the light cannot escape.\n\nEinstein has been tested hundreds of times and every time it has stood up to the test. Another key aspect of his theory that you should know that light is not relative. If a car is driving 20 miles per hour and the headlights are on the light goes away from the car at light speed and a person standing on the curb will also see the light moving away at light speed. The speed of light is completely independent of reference point and that is why it makes the ultimate reference point
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I'll try to explain this in simple terms, but it's rather mind-twisting.  \nThese are the basic principles of Relativity:\n\n1. The speed of light is constant for all frames of reference.\n  Light goes toward you at the same rate no matter how fast you're moving away from the source.  As an example, think about someone throwing a ball at you.  If they throw the ball at 25 miles an hour and you run away from them at 10 miles an hour, then from your perspective, the ball will be approaching you at only 15 mph, because you are running away from it.  But with light, no matter how fast you run away from the approaching light, you will always "see" it coming after you at 186,000 meters per second.  But the light isn't speeding up.\n\n2. Time can speed up and slow down.\n  If you were to get in a rocket and zoom off into space going really fast (nearly the speed of light), and if you were to stay up there for a couple of years (still going really fast), you would come back to Earth to find that a couple of decades had passed.  In other words, even though you would have lived only two years, the people on Earth would have lived 20 years already.  This is because the faster you are moving physically, the slower time moves.  This is not noticeable in everyday situations, because the time change is less than a billionth of a second.  It's only a noticeable difference at really high speeds or with really sensitive atomic clocks, but it has been proven to be true.\n\n3.  No matter (physical thing made out of atoms or sub-atomic particles) can move at the speed of light, or any faster.\n  The faster something is moving, the more mass it has.  So if you were trying to accelerate something to the speed of light, the faster it got, the heavier it would get, and the harder it would be to make it go any faster.  Eventually, it would be too heavy to accelerate.  An object moving at the speed of light would theoretically have infinite mass.  Since light waves aren't matter (they're energy), they can move at the speed of light.  Same goes for gravity waves - they also move at the speed of light.\n\n4.  Space and time are meshed together in something called spacetime, which is sort of the "framework" for the universe - like the paper on which you draw a picture.  Matter (mass) bends spacetime.\n  Picture a trampoline.  If you were to place a ping pong ball on the trampoline, it would make the area below it sag a little bit, but it would hardly be noticeable, because the ping pong ball is so light.  But if you were to put a bowling ball there instead, the indentation would be much larger.  In the same way, larger masses cause more curvature in spacetime.  This concept has two consequences:\n\nA: The closer you are to a large mass, the slower time gets.  So if you were to get really close to a black hole, then time would slow down for you.\n\nB: Remember that going really fast gives you more mass?  Well, this why #2 works.  If you're in a rocket going nearly the speed of light, then your mass is going to be bigger.  That in turn means that spacetime will curve more around you, so then time will pass slower.\n\nThere's a lot morer to it than that, but those are the basics.
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An outside observer would say that the distance between you and the object is increasing at a rate equal to the speed of light, but if the object shone a light at you, that light would still reach you, in the observer's frame.  In the observer's frame, no object is moving faster than light, and there is nothing wrong with the relative separation of objects increasing faster than the speed of light in a frame of reference where both objects are moving.\n\nIn your own frame, you and the object would be moving apart at a relative speed of 0.8c.  Speeds do not add linearly when they are very large.
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There are plenty of good websites that answer this question, for any knowledge level. The concept is complex enough that you won’t get a meaningful answer here.\n\nIn horribly oversimplified terms Relativity simply  states two things. \n\nOne that there is no universal ‘at rest point’, it all depends on how you choose to define it. You sit in a car doing 100mph and I stand beside the road. Normally we assume that you are in motion and I am at rest. Relativity states that we can just as accurately say that you and the car are at rest and I am moving at 100mph. Alternatively, we normally believe that the Earth orbits the sun and the Moon orbits the Earth. Relativity states that it is just as accurate to say that the Earth orbits the moon and the sun orbits the Earth, or we could say that we all orbit some imaginary point in between all three. It is all a matter of choice what we define as being the fixed point.\n\nThe second is that the speed of light is constant regardless of whether you are at rest or moving, and regardless of how fast you move. If you are sitting in a car doing 9/10 of lightspeed and are going past me standing still beside the road and we both look at exactly the same light beam shining down the road we will both see that light beam travelling away from us at exactly the speed of light relative to both of us. You don’t see it slowed down just because you are travelling almost as fast as it is. It will move away form me just as fast as it moves away form you. \n\nThose are the basics, and they aren’t all that hard to understand, even if they don’t seem to make much sense. What Einstein did was sit down and think really hard about the logical consequences of those two points.
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No, the speed of light in vacuum is constant everywhere.\nLight follows the path of minimum energy (geodesics) in gravitational fields, which are bent around the masses.\n\nThe amount of bending at the surface of the sun is of the order of arc seconds. However close to a black hole the bending is so strong, that the light path bends around and around the hole, never to escape.
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The key point to this whole question is if you could travel faster than light.  Since at our present knowledge of physics says no, and our current tech is not able to get anywhere remotely near the speed of light let alone faster than it, we will assume this hypothetical question implies these two things don't matter.\n\nIf so, then yes you could see into the past if you had an adequate viewing device which could discern the light you would receive at the end of your journey--light which you left behind by going faster than it.  But to see exaclty the number of years in the past as the light year distance you travelled, you woould have to move instantaneously.  If you had any non-relativistic travel time, you would have to consider time of your journey to determine how far in past you were seeing.  If you travelled 1.1 times the speed of light, you would only get to see .1*light year distance in years past.
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The moment you hit the speed of light, time would stop for you, so it would be pretty hard (impossible) to turn the darn lights on!\n\nSaid another way, as you approach the speed of light, the outside observer sees you slowing down; when you hit the speed of light, it would take the observer an infinite amount of time to see any change in your state.\n\nNow, suppose you left your headlights on the whole way, what would everyone see?\n\nAs you approached the speed of light, the light is still reflecting off the objects around you, so the observer, and you, continue to see the reflected light. Once you hit light speed, however, the energy transfer required to turn heat into light wouldn't occur, so no one would see the photons. Of course, since you're traveling at the speed of light at that point, everyone would see you hit the object.\n\nOr this way... the light leaving your headlight changes it's frequency in proportion to the speed you're moving, once you hit light speed, the light would become matter! Of course, the wave packet that is light + your car wouldn't are too much, since time wouldn't exist for you anymore.\n\nHave a nice trip!
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The theory is that gravity, or magnetism, moves at a certain speed.  The last I heard, that speed is still unknown but under study.  Thus, if the sun disappeared the earth would remain in orbit at the "speed of gravity"  and it would remain daylight at the "speed of Light."   Which speed is greater is yet to be determined.  However, my guess is that the speed of light is faster than the speed of magnetism.
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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.
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Updated 1997 by PEG.\nOriginal by Philip Gibbs 1997.\n\n\nI am driving my car at the speed of light and I turn on my headlights.  What do I see?\n\nSadly this question and all others about experiences at the speed of light do not have a definitive answer.  You cannot go at the speed of light so the question is hypothetical.  Hypothetical questions do not have definitive answers.  Only massless particles such as photons can go at the speed of light.  As a massive object approaches the speed of light the amount of energy needed to accelerate it further increases so that an infinite amount would be needed to reach the speed of light.\n\nSometimes people persist: What would the world look like in the reference frame of a photon?  What does a photon experience?  Does space contract to two dimensions at the speed of light?  Does time stop for a photon?. . .  It is really not possible to make sense of such questions and any attempt to do so is bound to lead to paradoxes.  There are no inertial reference frames in which the photon is at rest so it is hopeless to try to imagine what it would be like in one.  Photons do not have experiences.  There is no sense in saying that time stops when you go at the speed of light.  This is not a failing of the theory of relativity.  There are no inconsistencies revealed by these questions.  They just don't make sense.\n\nDespite these empty answers, nobody should feel too put down for asking such questions.  They are exactly the kind of question that Einstein often asked himself from the age of 16 until he discovered special relativity ten years later.  Einstein reported that in 1896 he thought,\n\n``If I pursue a beam of light with the velocity c (velocity of light in a vacuum), I should observe such a beam of light as a spatially oscillatory electromagnetic field at rest.  However, there seems to be no such thing, whether on the basis of experience or according to Maxwell's equations.  From the very beginning it appeared to me intuitively clear that, judged from the standpoint of such an observer, everything would have to happen according to the same laws as for an observer who, relative to the earth, was at rest.  For how, otherwise, should the first observer know, i.e., be able to determine, that he is in a state of fast uniform motion?  One sees that in this paradox the germ of the special relativity theory is already contained.  Today everyone knows, of course, that all attempts to clarify this paradox satisfactorily were condemned to failure as long as the axiom of the absolute character of time, viz., of a simultaneous, unrecognizedly was anchored in the unconscious.  Clearly to recognize this axiom and its arbitrary character really implies already the solution to the problem.''\n\nIn 1905 he realised how it could be that light always goes at the same speed no matter how fast you go.  Events that are simultaneous in one reference frame will happen at different times in another that has a velocity relative to the first.  Space and time cannot be taken as absolute.  On this basis Einstein constructed the theory of special relativity, which has since been well confirmed by experiment.\n\nQuestions of relative velocity in relativity can be answered using the velocity subtraction formula v = (w - u)/(1 - wu/c2) (see relativity FAQ: velocity addition).  If you are driving at a speed u relative to me and you measure the speed of light in the same direction (w = c in my frame), the formula gives v the speed of light in your reference frame as, v = (c-u)/(1 - u/c).  For any speed u less than c this gives v = c so the speed of light is the same for you.  But if u = c the formula degenerates to zero divided by zero; a meaningless answer.\n\nIf you want to know what happens when you are driving at very nearly the speed of light, an answer can be given.  Within your car you observe no unusual effects.  You can look at yourself in your mirror which is moving with the car and you will lo
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Here are the postulates:\n\n(1) The laws of physics are the same as viewed from the perspective of any observer moving at a constant speed.\n(2) The value of the speed of light (denoted "c") is the same in every reference frame.\n\nThe first condition isn't very strange: You'd expect physics to be the same if you were on a very smoothly moving train as you would if you were standing on the Earth.\n\nThe second condition is very strange: Suppose you have two people moving with respect to each other.  One of them is moving at 1/2 the speed of light and the other is moving at 1/4th the speed of light.  Now, a beam of light is passing by them.  They'll both measure the speed of that beam RELATIVE TO THEIR VELOCITY to be c.  \n\nNote that this is a big contrast between what we'd normally expect.  Suppose you were moving at 7 miles per hour and I threw a ball past you at 10 miles per hour.  You'd see the ball moving away from you (another way of saying "moving relative to you" at 3 miles/hour because 10 mph - 7 mph = 3 mph).\n\nIn our light example we just saw that both observers measure the velocity of light relative to their own velocity to be the same.  It'd be like if your friend was moving at 5 miles per hour and you were moving at 3 miles per hour and you both claimed the ball was moving away from you at the same rate.\n\nAt any rate, what this is meaning is that neither time nor space is an absolute quantity.  If you were to observe a rocketship moving near the speed of light (as measured with respect to you), you would observe:\n\n(a) That the rocket appears to contract (shrink) in it's direction of motion, and\n(b) Events aboard the spaceship would appear to occur more slowly.\n\nHowever, they would measure the same things happening to you and the events along the spaceship to be proceeding normally.\n\nThat is only a very brief introduction.  If you'd like a better, but still accessable to a non-scientist, account of this I suggest you consider reading http://casa.colorado.edu/~ajsh/sr/sr.shtml .
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Yes.  The laws of relativity have been shown to be true at various speeds.  At slow speeds the effect is very, very tiny, so it is very hard to measure, but every bit of evidence we have says that relativity is true for all speeds (and for being stationary, for that matter).\n\nWhy is it hard to measure?  Well, say you're in a small (2 meter) automobile going 100 km/hr.  The contraction due to relativistic effects would be about .2 micron, or 200 nanometers.  To see a contraction of just two cm - just under an inch - you would have to get the car up to 95 million miles an hour!  \n\nTime, momentum, mass, etc are likewise.  They are affected relativistically, but the effect is so very small that for all practical purposes it is zero.  \n\nBut maybe you have an impractical purpose??  :-)
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Assuming you are standing still relative to the airplane, and the airplane is going at the exact speed of light... yes you would see it, but only as it colides into you.  if you are asking if you would see if before it hits you, then no.  Due to it's speed, all of the light coming off of it would not be able to outrun the plane.
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well first, read my other answer to your question about the speed of sound.  You would probably expect the answer to be the same, and the light to reach the other car, but this is a special circumstance because nothing can travel faster than the speed of light, not even light itself.  when a beam of light is shone ahead of a rapidly moving space vehicle, and is expected to be moving at the speed of light plus the speed of the vehicle, it is still only moving at the speed of light, which is puzzling.  Physicists have defined the speed of light to be the ultimate cutoff point for speed.\n\nAnd also, you wouldn't be able to travel at the speed of light anyway because time would probably stop since it does get slower and slower the faster you go.  Velocity warps time, the faster you go, the slower time moves for you relative to a stationary object.  I've read this, and it is definately true, we had to derive the formula in physics from, and calculate the time, lenghth(which decreases with speed), and mass (which increases with speed) distortion as well.  The effects of this are very negligable unless you are moving at speeds very very close to the speed of light, at least over 90% of the speed of light, and we haven't gotten anywhere close yet.  The denominator of this factor that time, length, and mass are distorted by actually is 1 minus the square root of the speed of light(c) over the speed in which the object is traveling (v), so the reason you can't go faster than the speed of light is because if v was greater than c, then that square root would be greater than one, meaning the denominator would be negative, meaning the factor would be negative, and the light would actually be travelling backwards in time...\n\nIf you find any of this interesting, I highly recommend "The Elegant Universe" by Brian Greene.
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It's not a yes or no question.\n\nCan one travel faster than the speed of light?  No.\n\nCan objects be moving away from each other at a relative rate faster than the speed of light?  Yes.\n\nMeditate upon this, and you may become enlighted, or enspeeded, or something...
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Hi Itsverystrange\n\nIt is actually true that distant galaxies can (and are) travelling away from us at apparently greater than the speed of light.  Any galaxies outside our Hubble volume (r = c/H) are apparently receding from us at greater than c - this is why they're outside our past light cone.  \n\nThere's no conflict with special relativity here because SRT is a strictly local theory.  The coordinate system itself is doing the expanding, the galaxies aren't moving with respect to their local coordinates.\n\nHope this helps!\nThe Chicken