[jeffc]

I tried looking up this information, but found nothing much: what makes light travel at any given speed; what governs it? Is it the maximum speed of an electron in orbit around a nucleus?

[EQAndyBuzz]

“I tried looking up this information, but found nothing much: what makes light travel at any given speed; what governs it?”

I am thinking the NRC or maybe the EPA governs it.

Sorry, habit.

[Da Coyote]

“I tried looking up this information, but found nothing much: what makes light travel at any given speed; what governs it? Is it the maximum speed of an electron in orbit around a nucleus?”

It comes from examining Maxwell’s equations, which completely define electromagnetic behavior. The speed of light (c) is an integral part of these equations...and is necessary to get all the rest of the measurement bits to fit. Einstein’s gift was to examine how one would have to “warp” these equations in order to explain what you would see if you observed an EM wave whilst moving...and the warping is the famous time change. The “speed limit” also arose from these equtions. Now, this speed limit is attached to things with mass, and also appears to be associated with the transmission of “information”.

We’ve already got examples of “something” happening at greater than light speeds when examining quantum interconnectedness...but this “something” does not carry information with it.

Things out there are much weirder than we know...which is what makes physics so fascinating.

[bagman]

Electrons really don’t orbit around the nucleus of an atom.

[Phlyer]

what makes light travel at any given speed . .

This arose from an earlier question, when it was not assumed that the speed of light is a fixed value. The question, colloquially stated, was: If light waves . . what waves?

There is compelling information (diffraction patterns, etc.) that light behaves like a wave. Yet there was no known way for waves to propogate without a medium - something to 'wave' or carry the energy. A substance called 'the ether' was postulated as a medium to carry the wave energy of light. If the ether were a property of space, then the measured velocity of light would change based on how the observer was moving relative to the fixed ether. In other words, if you were travelling along with the ether, you'd measure a lower speed for light, and if you were travelling against it, you'd measure a higher speed.

Michelson and Morley set up an experiment to prove this. But what they found was that the measured speed of light was independent of our own motion - it was always a constant.

Einstein - among others - explained this in various analyses including the theories of relativity - which provided very elegant, testable, and accurate ways to show they were consistent with all observed data. Maxwell's equations provide very elegant, testable, and accurate ways to calculate electric and magnetic effects, and the constant speed of light is integral to them. In essence, light waves are interchanging electric and magnetic fields, and Einstein showed that at one particular speed, these are self-sustaining even in a vacuum.

But, the speed of light is not really a constant. It is a constant in any medium, and it is fastest in a vacuum. The speed of light is inversely proportional to the index of refraction for the medium - which means the speed of light inside a diamond is less than half of what it is in a vaccum.

This new experiment measures the elasped time for neutrinos to travel a known distance - and compares it to a calculated time for light to travel that same distance. Neutrinos are funny things, and there may be interactions at a level where the strong and weak nuclear forces have a greater effect than electro-magnetic forces. So I'm not saying that neutrinos can't travel faster than light in the particular conditions of this experiment.

However, when the difference is measured in nano-seconds, it is on the same order as the accuracy of the measurements - and those are always questionable. Frankly, I think the answer will turn out to be an error in their analysis of their setup, but that's what a proper scientific method is all about - make a prediction, check it experimentally, and scrub your answer until no other answer (like missed analysis of timing, or of distance, or of something else) can explain the observed results as well as your answer.

Oh, and as another poster responded, electrons don't really orbit atomic nuclei. That's not really relevant to this.

[LesbianThespianGymnasticMidget]

Electrons dont really orbit. They have probabilities of being in any particular place in their electron shell. It is hard to grasp. See this video http://www.youtube.com/watch?v=DfPeprQ7oGc

[DManA]

One of about 20 fundamental constants of the universe. No one has a clue why they are what they are. But we know if any one of them were even slightly different we wouldn’t be here.