why does light have a fixed speed?

Question

is not light slowed down by gravity? can its speed be increased?

Answer 1

The fixed speed of light is an observation, that has held in all circumstances in which it has actually been checked (which is not to say it will always be true). Numerous experiments where conducted about the speed of light in the late 19th century, and the result was a puzzling constancy in speed. This was a big problem in theoretical physics around 1900. In Einstein's Theory of Relativity, the fixed speed of light is taken as an axiom, or prerequisite, of the theory.

In all of 20th century physics, the idea of a fixed speed of light was so successful, both experimentally and theoretically, that the idea that it might not be absolutely fixed was neglected.

As an aside, it needs to be pointed out that the apparent decrease in the speed of light in a non-vacuum medium is not of real theoretical significance---it is an approximation (and a really good one) used in optics. The photons do not really slow down in the medium, they are systematically absorbed and re-emitted so that they act exactly as if they were slowed down, and for experimental and engineering purposes, it is as if they were slowed down.

All that being said, it is possible that light does not have a totally fixed speed in vacuum in all circumstances. In a deep theoretical sense, it is not known why the speed of light has the value that it does. The speed of light is a connection between time and space that is taken to be immutable in all particle field theories, including string theory. But quantum gravity hints that the universiality of this connection may be somewhat bogus, or at least accidental, and possibly variable in very distant parts of the Universe (way beyond our event horizon). In some interesting speculative theories, such as "Doubly Special Relativity", photons that are extremely high energy can go faster than the cannonical speed of light.

Light is not slowed by gravity, it is redshifted to lower frequency. The photons coming out of a gravitational field lose energy, but they don't change their velocity.

Answer 2

Lights speed depends on the medium it's traveling thru. It can speed up slow down and recently single photons have been made to actually stop. the previous record was 38 miles per hour. It can also be sped up to over 300 times normal briefly.

gravity can slow light but no matter what "speed" light travels at it's always the 'speed of light'

Answer 3

Actually, light aka photons, have been slowed in the lab. Gravity can 'bend' light around the gravity well of large objects. There is no way to accelerate light beyond it's constant velocity in the 'known' universe according to Einsteins physics. However, anything is possible, and quantum physics experiments have uncovered some mighty exotic properties of matter. With the new particle accelerator in Bern, even more strange things might be uncovered. If, as some are convinced, we may be living in only one of many universes, in one of many galaxies. Light may behave differently in another dimension.

Answer 4

The speed of light in vacuum is determined by the properties of space. James Clerk Maxwell was the first to calculate it.

Gravity does not slow light; it warps space.

Answer 5

no one knows WHY light has a fixed speed. But as far as we have experimented, it does.

of course that's light in a vacuum. When not in a vacuum you can play various tricks, and "slow it down" to much, much slower speeds.

gravity does not slow light down, but it will (1) make it follow a curved path (or rather, a straight path in curved space) and can eventually capture it, as happens in a black hole; and (2) gravity will increase the wavelength

Answer 6

light can't be slowed by gravity because light particle have just a little mass.gravity effects it but in a very slow amount.but it slows down in different medium.but the speed of light cannot be increased.

Answer 7

Light has a fixed speed in a vacuum. That is its maximum speed. It can be slowed by passing through media such as glass or water.