A question about light speed.

[Rota]

I accept the speed of light is approximately 300 million meters per second. I am willing to hear the argument that the speed of light is the "speed limit" of the universe. But, that's not what this thread is about. My question is...

Can light move slower than the speed of light?

Does a little electron of light-energy ALWAYS travel at the speed of light? Can a beam of light-energy travel at a paltry 100 million meters per second? If energy is moving slower than the speed of light, then is it no longer considered to be "light?" Is it now some other kind of radiated energy?

The speed of light is a constant (c) in many physics and math equations. But, is the speed of light constant? Or is (c) really just the maximum speed of light?

[TCWNME]

I know of a laboratory somewhere where they are able to slow light down somehow, but I can not remember how, or what it is called. I guess it is time to go looking.

[Fallbreeze]

I would think that there would be a way. It would be very hard to imagine light couldn't have a variable speed. Then again, I'm no physics major. :P

[Rota]

I know of a laboratory somewhere where they are able to slow light down somehow, but I can not remember how, or what it is called. I guess it is time to go looking.

I know light can be delayed by detouring it. As light passes stars and planets the gravity well bends it's path. This means it takes longer than the speed of light to get from one point to another (as the crow flies). But, the speed hasn't actually been slowed. The length of the path has just been increased between the two points.

On a map, two cities may be 100 miles apart. Traveling at 50 miles per hour will take 2 hours to get there. But if there is no direct road between the two cities. The route to travel between them uses 125 miles of road. It actually takes 2.5 hours to get there, even though you are traveling at the exact same speed of 50 miles per hour.

I'm curious if the experiment you discuss is truly slowing down light's speed, or simply delaying it's path.

[Super DurtSS10]

where do you come up with these questions btw rota lol

[Rota]

where do you come up with these questions btw rota lol

A dream last night. These are the kind of thoughts that keep me from getting a good night's sleep.

While restlessly trying to get to sleep one night, I figured out a device that could potentially create artificial gravity for a space station. My brain thinks of crap like that all the time.

[TrulySorry]

This is as you say"copy pasta" from this site http://www.school-for-champions.com/...lightspeed.htm

For those to lazy to look
Speed through matter

The speed of electromagnetic waves passing through transparent matter is slower than it is in a vacuum. Glass is transparent to visible light, radio waves will easily pass through non-metals, and x-rays pass through most materials except lead.

Most measurements of the speed of light are made in the atmosphere. Since the effect on the speed when passing through air is so very small, the speed of light in air is almost the same as it is in a vacuum. The difference is negligible.

The reason electromagnetic waves travel slower though transparent materials is the effect that the electrons have on the waves. They act somewhat like a "friction" on the waves.

Light through glass

The fact that light moves slower through matter can be seen when visible light passes through glass. If you shine a light at an angle through a piece of glass, the light beam will be bent or refracted.

(See Refraction of Light for more information.)

The ratio of the speed of light in vacuum divided by the speed of light in the material is called the index of refraction for the material. The index of refraction of glass or other material indicates how much slower the light travels through the material than in a vacuum.

Typically, the index of refraction of glass is from 1.2 to 1.5. That means the speed in a material of index 1.5 is 66% of the speed in vacuum.

Extreme slowing

Although the speed of an electromagnetic wave through matter is can be up to 50% less than the speed through a vacuum, scientists were able to greatly reduce the speed through matter in special situations. This was first done in 1999.

Danish physicists performed an experiment where they slowed light down to only 38 miles per hour or about 57 kilometers per hour. They did this by sending a beam through a material made of sodium atoms cooled to near absolute zero (-273?C or -460?F). They achieved this low temperature by using lasers to slow down the atoms, through a special method used in quantum mechanics called the Bose-Einstein condensate. (Explanation of this goes away beyond the scope of this course).

Speed is the maximum
The speed of light is supposed to be the maximum speed at which matter can travel.
I guess light is slowed through matter-TS

[Bree Fletcher]

edit: i would imagine that light getting sucking into a black hole probably loses some of its speed, but i have no idea how that works.

Well, as a little thought experiment...

Say you were, (doen't matter how, just go with it) just barely outside the event horizon, and were shining a beam of light directly away from the black hole. I think the gravity should be enough to reduce the light's speed, though it's still capable of moving away from the black hole. On the other hand, it's nagging at me that there's something ese that comes into play, some sort of strange relativistic thing, that would mess with time and force it to keep that speed, I'm not sure...

Anyone want to help there?

EDIT: Duh, Trulysorry, you're spot on. I forgot about refraction indexes and all that. That is precisely how to slow down light.

[Rota]

Good find, TrulySorry. So, light can be slowed down with simple friction. That's good to know.

+rep

[pialpha]

The speed of light is a constant (c) in many physics and math equations. But, is the speed of light constant? Or is (c) really just the maximum speed of light?

The constant 'C' is the speed of light in a vacuum, so it is constant. I'm not too sure about anything else though.

Also, @Truly

It goes slower through those materials because the photons hit particles on the way through, I think this question is asking about whether it still travels at the same speed as in a vacuum when it is bouncing around.