Regarding the Speed of Light?

Question

The speed of light is said to be a constant.

Is the above a fact or an assumption since we cannot observe anything that moves faster than the speed of light?

( I would like answers from people who actually know this stuff, not just speculation )

Answer 1

In 1887 Albert Michelson and Edward Morley conducted a series of experiments trying measure the speed of light. A little explanation will help getting the point of what they were doing.

In water, waves like those a boat makes travel at a well defined speed, but something you will notice is that if you are on a river the speed of the waves is different if the wave is moving "with the flow" (down river) or "against the flow" (up river).

They reasoned that if the light wave was moving "in something" called the "aether, or ether" then we should see the same effect. So, they set up an apparatus and then measured the speed of light as the earth moved around the sun. As the orbit of the earth changes, the position of the earth in the aether would be changing and we should see the speed of light change.

Nothing happened. No matter how the test apparatus was oriented, the speed of light was the same. Uh oh. Bad doobies, as they said "back in the day."

Along comes Einstein who says, "OK, we need to fix things so that the speed of light is the same for every observer who is in a frame of reference where the is no acceleration (an inertial frame)." It turns out that the simple assertion that "the speed of light is a constant in all inertial frames" means the same thing as "nothing can go faster than light." No matter how fast you are going, you will always measure the speed of light as 2.99 x 10^8 m/sec. In order to make the laws of physics work like that then light speed is an absolute upper bound.

So far, there have been no measurements of "things" traveling faster than "c" in free space. So, to answer your question directly, it is not an assumption, but it is conceivable that something could break light speed. If that happened, the whole of physics would be re-written. Given all the experimental evidence up to now, people have great confidence that "c" is an absolute upper bound.

HTH

Charles

Answer 2

The Michelson Morley experiment compared the speed of light travelling in different paths on Earth. Because Earth is moving (around the sub and the sun through the galaxy etc), this means the relative motion of paths in different directions is different. They found no difference.

Many theories were given for this, including expansion and contraction of bits of the equipment depending on which way it was moving.

However, Einstein made an assumption that the correct answer was that the speed of light in vacuum was always the same, regardless of how the observer was moving. He fed this as an axiom into his theory of Special Relativity.

Now SR leads to predictions, and these predictions have been widely tested experimentally. The fact that SR is shown correct in these experiments supports the axioms it is based on, so shows that the speed of light is indeed constant.

Answer 3

There are 2 factors to this: experimental and theoretical. The speed of light has been measured to very fine precision to be a constant value. In fact, whenever you use your GPS it relies on the constancy of the speed of light.

There is also the theoretical. Special relativity says the speed of light is constant, and that theory has been tested time and time again and appears to be accurate.

One way to think of it is that every particle, including you, is moving at the speed of light in the space/time continuum. There are 4 dimensions - you (and I) are motionless, or at least very slow, in the 3 spacial dimesions, which means almost all our movement is in the time dimension. As the speed in space increases the speed in time decreases, which is why going nearly the speed of light is like a time machine to the future. For a photon, 100% of its speed is in the space dimensions, which means its speed in time is 0 - for photons, no time has passed since the big bang.

I have sometimes wondered if the speed of light could be a local constant, which changes with time - for instance, rather than the universe expanding the speed of light getting slower would have much the same effect. I have never heard of anyone deal with this speculation, the answer to your question is that, as far as we can know any scientific data, yes, the speed of light is a constant.

Answer 4

My awareness is that the cost of light is continuous from the attitude of the observer: If it extremely is genuine then you definately, traveling merely below the cost of light could see the beam take off merely as in case you have been status nonetheless. An Observer off to the facet although, could see the beam of light circulate previous to your astounding speed at 10 ft/sec. swifter than you your self are traveling. i think of I actually have a headache now, i'll think concerning the hollow concept of electric powered circulate. or maybe if the North Pole is truly the South magnetic pole because of the fact the N on the compass factors to it. Or is the Compass categorized backwards to start with?

Answer 5

I dont know who said that the speed of light is constant .Experiments have shown that its not constant, and the velocity of light continually changes especially when it bends.
It appears that gravity can change its velocity.
No one has measured the speed of light at the outskirt of the Universe. We have only measured it relative to the earth.
The smaller a mass is the faster it travels. Hence a light particle being the smallest mass is the fastest moving invariant mass of the Universe.

Answer 6

actually the speed of light in a vacuum is the constant, c, that they are referring to. particles can exceed the speed of light in suitable gaseous mediums other than a vacuum, in fact one of the experiments due at CERN this year is the High Momentum Particle Identification Detector (HMPID) which uses an effect of a particle travelling faster than the speed of light, called Cherenkov Radiation, to calculate a particles mass, so we really can observe particles above the speed of light...I've attached the link to the HMPID at CERN for your reading pleasure...

Answer 7

Not anymore.
It has been proven that light is not "C"