Speed of Light?

Moving at the speed of light? Can we do it?

 

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not sure, maybe you should consult some books by einstein perhaps. Are you talking about the human body going faster than light or what?

 

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Moving at the speed of light? Can we do it?

Any object with mass cannot move at the speed of light.

 

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Im asking if its possible to accelerate anything to the speed of light.

Maybe by converting matter into anti-matter?

 

No. Nothing massive can go the speed of light.

You can't convert matter into anti-matter. It would break a whole slew of conservation laws.

- Warren

 

Antimatter is just a mirror image of matter. It still has mass, so would require the same infinite energy to go that fast.

Now, if you were talking matter-antimatter reactions to produce the energy needed, you could possibly obtain a good fraction of c. But as you get closer to the limit, not even total energy conversion of whole stars will push you fast enough. And time dilation makes it a one way trip as well.

Only way to "break" the light barrier is to find some unknown loophole, like the folding of space, wormholes, and such, so you somehow bypass the space you were previously trying to travel quickly through. But so far all that's just science fiction.

 

Ok so you can't make something with a mass go the speed of light. But could you convert the object you are trying to move at the speed of light into something... maybe energy?

 

Well, you can convert matter into energy, then beam it somewhere at the speed of light. Converting it back is another matter (no pun intended

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).

 

yup

your spirit is light!

meditate

 

neutrino

sorry...i'm not an expert...but can't an neutrino exceed the speed of light...i thought i heard this once, but am not sure anymore...

edit: after some searching i noticed that most sources conclude that neutrinos do not travel at speeds excess of lightspeed, unless you want to believe some more contraversial theories...

 

Re: neutrino

Neutrinos certainly do not ever travel faster than light. They do, however, tend to travel at very nearly the speed of light. The current upper experimental limit of the electron-neutrino mass is 3 eV, which is practically nothing. It may well be that the neutrino is indeed massless, and therefore must go the speed of light, exactly.

- Warren

 

Here's what I've been thinking lately and it messes me up (Please help me): Speed is a relative term. I can only say how fast I'm going in relation to another object. To say I'm "moving at the speed of light" doesn't really mean anything unless I provide a reference frame as to what that means.

Is it not then, that the speed of light becomes the fastest possible speed compared to a "stationary" reference frame? If so does that apply even if you are travelling close to the speed of light compared to something else? I mean, in that reasoning the speed of light is always changing relative to the universe but remaining the speed of light compared you whatever reference frame you happen to be in right?

I'm prolly messing something all up with that. Is the reference frame for the "speed of light" from a star, the star itself and if so how do we know how fast IT is travelling? Is it just that the speed of light is SO fast that other speeds just don't matter relatively? Like the frame of reference becomes pointless because regardless of what you compare it to the leftover (the speed of light minus whatever you're comparing it to) would be not enough different from the speed of light to bother stating that it's different? That doesn't seem right to me since well, some stuff is really really fast. Any input?

I guess it's pretty much the old "If I'm travelling at .9c and I turn on a flashlight, what happens?" thing. Messes my head up. Would the "stationary" observer see the light from the flashlight? Would that light not be travelling "faster than light" compared to a stationary observer?

 

wesmorris,

You're stuck on what's called the "emitter theory," which was a widely held belief before the introduction of special relativity. The emitter theory holds that the speed of light is not constant -- the speed of light relative to the emitter of the light is constant. According to emitter theory, if you were travelling at 0.9c and turned on your flashlight, a stationary observer would measure the photons going 1.9c.

Well, this doesn't happen. It turns out that the speed of light is constant to every observer. Futhermore, it's always the same constant, namely 3 x 10^8 m/s. Every observer, no matter how fast he's moving, will always measure the same speed of light. This is in agreement with the so-called Galilean equivalence principle, which states that one cannot detect his own uniform motion through space.

So emitter theory is wrong -- if you turn on your flashlight at 0.9c, you will measure the speed of the light at 3 x 10^8 m/s. A stationary observer will, quite surprisingly, also measure the light as going 3 x 10^8 m/s. This would seem to be a huge contradiction -- except that the mathematics predicts two very weird effects. One is that time "slows down" for the guy travelling at 0.9c, as seen by the stationary observer. The stationary observer will see his buddy flying past, but will see all of the physical processes running slowly -- the batteries in the flashlight are discharging slowly, the buddy's heart is beating slowly, etc. This effect is called time dilation.

The buddy going 0.9c will not detect the change -- he'll still feel as if everything is running normally. In fact, he'll see his stationary buddy's clock running slowly, too. As you said, velocity is not important -- just relative velocity. Either buddy is free to consider himself stationary, and his buddy in motion.

Another effect goes hand in hand with time dilation: the stationary buddy will measure the length of his buddy as being contracted. If he's going 0.9c, the buddy and flashlight will all appear to be rather strikingly shrunk in the direction of the velocity vector. This is called length contraction. Time dilation and length contraction are effectively two sides of the same coin. They both occur hand-in-hand.

This all sounds wacky and ficticious, simply because most people aren't used to looking at things going a significant fraction of the speed of light.... but particle physicists are. The particles in accelerators can be pushed to a few parts per million of the speed of light. When this is done, we see that the lifetimes of unstable particles are dilated, exactly in accordance with special relativity. When these fast-moving particles emit light, we measure the speed of that light as the usual 3 x 10^8 m/s. Emitter theory is wrong.

Relativity (both special and general) are some of the most precisely tested scientific theories to date -- and both theories have so far passed every test thrown at them.

- Warren

 

Thanks that was very informative. Interesting, so like, there's a top down always valid reference frame. That is funky. I'm a huge Scientific American fan and spent a lot of time thinking about time dilation after the issue a couple of months ago focused on time and such.

Doesn't matter eh? Speed of light is the thing, regardless of how fast you go compared to anything else, the speed of light is always the same. Hurts my head.

 

Unfortunately, I don't know what you mean.

May I suggest that you go buy a book on introductory relativity? I can suggest Richard Feynman's "Six Not-So-Easy Pieces." It's cheap, easy to read, and covers special relativity rather nicely, IIRC.

That certainly is the way things seem to be.

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- Warren

 

I heard somewhere that if you travel from point A to point B going the speed of light more time would pass for the people watching you then for you. Is this time dilation, or am i wrong?

 

This is called the "twin paradox." It is an example of time dilation at work.

- Warren

 

What I mean is, it seems given the logic you gave me, that it is implied that there can be no zero reference frame that is universal. I mean, I cannot point to an object and say "that's sitting still" without comparing it to another object. Apparently what you've told me is that there IS an opposite extreme. Doesn't matter how fast you're going compared to what (it may be important, but not absolute) until you start talking about how close to the speed of light you are travelling... hence "top down". The only valid universal velocity becomes c eh? something like that? Eh, I'm just trying to extrapolate. Not sure if I'm doing a very good job though *shrug*. Could be nothing to it.

 

A physicist would simply say that there is no "absolute standard of rest" or "absolute frame of reference."

Yes, I suppose I can see where you're going with this. There is no standard of rest, but there is a speed limit. In a sense this is true, but perhaps not in the way you think of it right now.

Think about this: it is possible for two objects to approach each other at what a third observer would expect to be a velocity "faster than light." Two rockets approach the Earth in opposite directions at 0.75 c, for example. You might expect that each rocket would see the other going 1.5 c, but special relativity changes this "common-sense" rule for adding velocities. It turns out that special relativity says that each rocket would observe the other only going 0.960 c, due, if you will, to time dilation.

Since there is no standard of rest, there is no standard for "speed limit" either.

- Warren