Why is the speed of light the cosmos' apparent speed limit?

Question

What I mean is, does light simply travel at the fastest possible speed possible so therefore we know it as "the speed of light". Or is it the fact that it is light itself that is travelling at that speed that means nothing can go faster.

For example, if light travelled a few seconds slower than it does, would that then be the fastest possible velocity.

I probably haven't explained that very well. Does anyone know what I'm on about?

(PS: I'm already aware of E=MC 2 etc)

Interesting answers, thanks. I'm not asking whether it's a coincidence that light travels at the fastest possible speed, just whether - due to it's particular properties - light will always travel at the maximum possible velocity.

Also, I said that I'm already aware of E=MC 2, because I felt quite sure that someones answer would be an explanation of that.

Perspykashus - THANKYOU!!!! Indeed, I think you are the only person who knew what I meant. Much appreciated!

And Super Goob, actually, too.

Answer 1

I think I understand what you mean - slightly different from the tenor of most of the answers.

The answer is that it is the fastest speed because it is light (or electromagnetic radiation, to be more accurate). In Einstein's famous thought experiment, when he first started considering special relativity, he envisaged himself travelling at the speed of light and then wondered what would happen if he switched on a torch. The point is that there is something very fundamental about electromagnetic radiation travelling in our space/time. Nothing can reach point B from point A in a vacuum faster than light (lets not count tachyons!). The maths can be fiendish but, put simply, the answer is, "Yes, the fact that it is light itself travelling at that speed means that nothing can go faster".

Hope this helps.

Answer 2

Light can travel slower than the speed of light in a vacuum, when it goes trough some material, like glass, water or air.
The real speed limit is speed of light in a vacuum.
Why is this the limit? Well, relativity states that this value should be a constant, no matter how fast you are traveling, or how fast an experimenter you are observing is moving while measuring the speed of light. Thus this defines the fastest way information can propagate. And something moving is information, anything is information.
The other consequence is that the faster you move, the slower time gets -- from the perspective of an external observer that is. On board the fast rocket, you are slowed the same as your clock, so everything seems normal to you; but an outside observer would see your clock being slower than is own, and you mass increase at the same time. As you get closer and closer tyo the speed of light, your time slows more and your mass ncreses, and if you were to be able to get to the speed of light, your time would STOP and you mass would be infinite; this increase in mass by itself explains why you can get any faster, you'd need all the energy of the universe and then some to accelerate further.

Light has no choice moving at the speed of light, because photons at rest have no mass. But light must carry energy, so the only way for it to contain some energy is to travel at a speed where that zero mass (and thus energy) is multiplied by infinity so that we get something that is some definite value; and the only way to get that infinite value in there is to travel at the speed of light.
So, no matter what the speed of light in a vacuum turned out to be, that is the limit. If one day the speed of light was to change, that would change the limit.

Answer 3

Interesting question really. If light travelled a few seconds slower than it does... I'm tempted to say it would travel a few seconds faster. Light goes at the cosmic speed limit because its the cosmic speed limit - implying light could be a different speed is almost like imagining that the fact that it does go that speed is a coincidence!

Light traces a path in space time. Space and time are interlinked, energy (particles with zero rest mass) travels at the speed of light in a vacuum.

Its not an arbitrary limit if thats what you mean. Various authors have summarised Einstein's special theory of relativity better than I'm doing here. You need to understand that its the cosmic speed limit because accelerating anything up to the speed of light would requite infinite energy - even to accelerate a single atom - and that doesnt exist.

Anything with zero rest mass would travel at the speed of light and remember that light is all electromagnetic radiation from radio waves through ultraviolet and gamma rays too.

I'm not sure I'm explaining this well. The Fabric of the Cosmos has sections on relativity which are probably explained better than I can do.

Answer 4

I think it's because light has no mass, therefore if that's the fastest it can go, certainly things which do have mass can't go any faster. I guess the fact that light travels that fast is more a way to indicate the maximum speed than to dictate it. But since light pretty much travels as fast as it can, the only way it would slow down is if the speed limit did too.

Answer 5

The problem with travelling faster than the speed of light is that you are technically travelling faster than time itself. I will give you an example: the light form the earth at this time yesterday is travelling out into space, if you were to travel into space faster than light you could go out past where this light has got to and look back. What you would see is what happened yesterday. Then, if you travelled back toward what you can see faster than light you have, technically, travelled back in time. The problem with this theory is that if you travel faster than light you are not apparent to anything that is sub light so, in theory, you could never slow down. Of course this theory could be blown out of the water in the future when new technologies are developed, remember that Victorians thought that if a train travelled over 100MPH the air would be sucked out of their lungs and they would suffocate! There are certain laws of physics that can never be changed, all that changes is our understanding of them.

Answer 6

As Says Me saidE=MC 2 has nothing to do with light speed , but it has do with how much mass an object has before it changes into energy, or energy becomes matter.

What you wanted to know its Einsteins Special Theory of Relativity, which deals with light speed and time. And it's paradoxes.

And it depends on who is doing what, either the observer is is doing thetraveling or who is doing the observing ..the faster you go closer to the speed of light the slower time is for you and your perception of it Than the person who you left behind.
Example the thought experiment with sending one twin ona fast space ship to and from the center of our milkyway galaxy, and a return visit, He'd return to a charred planet with a white dwarf star nd he wouldn't aged at all and his twin ahve died thousands of years ago.

Answer 7

The answer to this comes in two parts. First is that of the basis of the movement, then what the value of "c2" means.

The basis of "c2". The basis of this value is found in the physics trilogy, which is: E = mc2, m = E/c2, and c2 = E/m. Notice that in each of these expressions that the only value that is unchanging is that of the "c2" value. The reason for this is that "c2" is the basis of both energy and mass. Or, energy and mass have as their composition the value of "c2", in form of electromagnetic energy. This must exist as it does in order that present time becomes that of the past. This value also demonstrates that everything in our universe moves from the present into becoming that of the past at the speed of light - c2. Lastly, there is no such entity as a "past" or "future" for mankind to travel to - such things cannot exist. All that shall ever exist to mankind in our universe is the "present". Then, notice that the duration of present time is that of the speed of light, and then it exists no longer. This, if one were to consider the ramifications, means there exists nothing that mankind precieves that exists in the present. By the time we precieve any form of reality, it has already passed into the past. In fact, everything we consider has to do with the past. There is nothing of the actual present that mankind recognizes.

Then we pass onto what the actual value of c2 becomes. This is not just a numerical value. It is not an abstract concept that seems to fit with reality. This value is demonstrated in the above equation of c2 = E/m as having an energy value. This is obvious in that it is the force of gravity that is the source of hydroelectric power, as it pulls water downward through large turbines that in turn form electrical power. The value of individual gravitons appears to be that of the value of "h", or Planck's constant.

There are a few sites that may be of interest to you:
http://360.yahoo.com/noddarc
http://timebones.blogspot.com

Answer 8

we know of nothing that travels faster than light - it is the limit by default ( for now )

there is nothing special about light - it is just a waveform - the theory is based on observation not on some calculation that puts light as the maximum speed limit

and E=MC2 does not really have to do with the speed of light - just the energy potential in any mass traveling at any speed

Answer 9

If you are aware of E=MC2 then you would know that to power an object to approach the speed of light takes enourmous amounts of energy.

I don't know the source but I did read in the last few months that to get an object to the speed of light would take up all the known energy in the universe.

The theory of this claim? E=MC2

Answer 10

Well scientists have recently managed to slow light down so much you can RUN faster than it - weird but true: - http://www.hno.harvard.edu/gazette/1999/02.18/light.html is one link but there the speed was only reduced to 39mph, it HAS been since reduced even further.

There are a few problems with E=mc squared

1. the figures get HUGE but at no point do the reach infintity. Foe example, mass of 1g * 3E8 * 3E8 = 9E16. HUGE - but it isn't infinte.

2. This assumes mass >0 what if you have 5g of anti-matter in a magentic suspension of 5g regualr matter. Net mass = 0

3. Time appears to be distortable at speed - indeed clocks and watches DO slow down / speed up on jet aircraft - interestingly depending on the direction of travel.

So as we can slow light down so much that we can run faster than it, I do NOT accept that we must regard light as a fixed limit anymore.