Is the speed of light really constant?

Question

If so what aspect of light does a black hole affect?

Answer 1

The speed of light *in a vacuum* is constant. Light does slow down as it passes through a transparent medium, like glass or air.

A black hole does not affect the speed of light. But the escape velocity of a black hole is greater than the speed of light, so once a photon enters a black hole's "event horizon," it will never come out.

Answer 2

The value of "c" is a universal constant - it never changes. It also happens to be how fast light travels in a vacuum, because, as Einstein demonstrated, it's the universal speed limit.

Light itself, however, is slowed by varying amounts by the materials it travels through. Common materials can cut the speed of light in half while it travels through them. Laboratory experiments have slowed light to the speed of crosstown traffic, and even brought it briefly to a complete halt.

A black hole does not change the speed of light; it warps space-time to the extent that light can't escape. Einstein showed that gravitational fields cause time to slow down. A black hole has such a powerful gravitational field that time actually stops. So light is still traveling at 186,00 miles per second, but that second never happens.

Answer 3

No, it travels at different speeds depending on the medium. The difference is small enough that it's considered constant. In addition, the only medium we generally discuss light traveling through is space--a vacuum--and since all of space is essentially uniform, the speed of light can be considered a constant for all intents and purposes.

Light is subject to gravity, but light isn't trying to escape from the black hole--it's just influenced to move toward it. Once the light is swallowed up by the black hole, we can only hypothesize what happens at that point. In any case, its speed would certainly change since, well, it's now in one of the most dense places imaginable in comparison to having nothing to impede its progress in a vacuum.

Answer 4

The speed of light changes as it enters/exits different media. For instance, the speed of light in water is less than the speed of light in a vacuum. It is, however, constant while it stays in water and constant as it stays in a vacuum.
A black hole affects or warps the space around it, so it will change the path light takes. Light still travels in a line, but the line is curved around the high gravitational field. The line is straight but space isn't, so to speak.

Answer 5

One consequence of the laws of electromagnetism, i.e. Maxwell's equations, is that the speed ''c'' of electromagnetic radiation does not depend on the velocity of the object emitting the radiation; thus for instance the light emitted from a rapidly moving light source would travel at the same speed as the light coming from a stationary light source. If one combines this observation with the principle of relativity, one concludes that all observers will measure the speed of light in vacuum as being the same, regardless of the reference frame of the observer or the velocity of the object emitting the light. Because of this, one can view ''c'' as a fundamental physical constant (1).

The person to discovered this tidbit was the Scottish physicist James Maxwell who in 1862 reasoned that light must consist of electromagnetic waves and that the speed of the wave in empty space would be exactly equal to the ratio of the electromagnetic and electrostatic units of electric charge (2).

Answer 6

Well, neither of the first two answers were really accurate.
Light can be bent, but still travels at the same speed. Black holes gravitational pull is similar to running a light beam past a super powerful magnet. It can disrupt or even absorp the signal, but cannot alter the speed at which it travels. It is a constant.

Answer 7

It is relatively constant but is affected by the medium in which it is traveling to some more or less degrees.
A black hole affects the visible light bands for sure. The radiation caused by the black holes energy is released though.

Answer 8

Yes to the first question. A black hole will affect the entire spectrum of light. That's one reason the abyss is called a black hole.

Answer 9

Light is not a constant. Don't know much about black holes, no one really does.

Answer 10

The speed of light is constant only to the very edge of decimal places over to the right (as in, to the 14th exponent)... it is rounded to our rounded measurements for time. It is used as a constant since with all tests, our current technological equipment cannot detect such a minuscule change.
With your follow-up question, are you referring to the "event horizon?" Well, that's where not even light waves escape...