Is the speed of light always the same?

Question

My father has the idea that maybe, just maybe after a beam of light has traveled through space for a few million light years, it might slow down a little. Any thoughts on this subject?

Answer 1

Never, the speed of light is always constant, unless what it goes through changes. For example if the light is going through water then WHILE ITS IN the water it will be going at a different speed but it still enters your eye at the same speed. Even if you're moving towards light or away from light the speed is the same.

Answer 2

Your father is not alone in his idea, but the speed of light will always measure the same, in any local condition it is measured in. It measures the same whether moving against the earth's rotation or with the earth's rotation. The clock's tick is not constant, but the speed of light is always constant to the clock's tick, so it will always measure the same in any locale.
Actually, because the clocks tick is moderated by motion, light should accelerate into the stillness of interstellar and intergalactic space. This is shown to be true with light echoes, where the light of a supernova is reflected off of surrounding space debris to show a growing light ball expanding much faster than what we should expect by Maxwell and Eintein.

Answer 3

Yes, the speed of light is always the same. It does not get "tired" as some uninformed folks speculate. Remember your high school physics text? It said it like this: The speed of light is 286,000 miles per second IN A VACUUM. Space being a vacuum, light ain't a'gonna slow down, yo.

Answer 4

The actual velocity of a light wave is determined by it's inertial reference frame.

It doesn't vary by much under most circumstances, but it can be slowed down.

In recent experiments involving cryonic lasers, solid lasers cooled to near absolute zero and exposed to electromagnetic fields, photons were proven to move very slowly indeed.

The researcher said they could introduce light into one end of a solid cylinder, go take a coffee break for twenty minutes, and when they got back, the light would just be reaching the other end of one meter long rod.

So yes, the realized velocity of light is variable. I say this is due to the denisty of all other quantum field energy in the environment (reference frame).

i.e., gravity fields, magnetic fields, electricfields, weak nuclear fields and strong nuclear fields.

However, in free space (best refered to as "Space-time") the speed of light is constant. (I think Space-time is a bit inconsistent, that light does vary in velocity a bit as it comes to us from distant sources, but this is because the reference frame changes a little. This is the same as light being blurred a little as it comes thru the atmosphere).

The interior of a laser rod, would be considered an "inertial reference frame" just as free space-time is a reference frame.

Now, if your reference frame emits light into free space-time, the speed of that light will not exceed "c" the speed of light.

In Einstein's gadanken experiment, two ox carts approach an intersection at 90 degree angles(crossroads). He proved that you cannot add to the maximum speed of light (for your reference frame).

If you were riding in a car, and shined a light to the front in the direction of your motion, the light may not be moving at free space maximum, but it would not have the speed of your car be added to the speed of the light. This would produce optical illusions in our daily lives that we know do not occur.

If you are riding in a car and you throw a baseball to the direction you are driving, the speed of the baseball is the speed of your throw, PLUS the speed of the car.

not so with light.

Answer 5

Speed of light, as far as I know, is constant. The speed of light, in my understanding, is an artifact of the overall limitation of a massive object to be in motion in space-time (e.g., moving forward through time at some % of full speed relative to others, and moving through the spatial dimentions at some % of C, but never 100% of either). This is not my idea, just how I understand how I read it.

Answer 6

"Even if you're moving towards light or away from light the speed is the same."

Unless of course you are moving away at the speed of light. If that were to happen you wouldn't see anything. That would be like trying to smell something up wind and the diffusion rate of the source is slower than the wind.

Answer 7

the speedof light is a constant that will not alter no matter where it travels. Light travels at a speed of 186,000 miles a second or 700 million miles an hour

Answer 8

As measured in a vacuum, yes, independent of any motion of the observer (Michelson-Morley experiment). In material objects, it is usually slower, by a ratio called the index of refraction. There are special cases where it appears to be faster, but these cases do not admit of transferring information at faster than the speed of light.

Answer 9

Well, that might explain the doppler effect. as an object that is moving away slows down, the light from it turns red which means slow, an object coming at you at high speed shows blue light which is fast light. so there you go.And don't forget gravity bends light, when it is bent it slows down

Answer 10

well the jury is still out on light. at first it was thought to be a wave form. like radio waves. then it was thought to be in pulses. but then it was proved that both are true. a prism is bending and slowing light to show colors. recently (in the 1990's) they proved that in certain substances they could speed up light in one experiment a light came out of the substance even before it went in!!!!