Are we postive light travels at the same speed everywhere in the universe.?

Answer 1

No, it isn't the same:

The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning "swiftness". It is the speed of all electromagnetic radiation in a vacuum, not just visible light.

In metric units, c is exactly 299,792,458 metres per second (1,079,252,848.8 km/h). Note that this speed is a definition, not a measurement, since the fundamental SI unit of length, the metre, has been defined since October 21, 1983 in terms of the speed of light: one metre is the distance light travels in a vacuum in 1/299,792,458 of a second. Converted to imperial units, the speed of light is approximately 186,282.397 miles per second, or 670,616,629.384 miles per hour, or almost one foot per nanosecond.

Through any transparent or translucent material medium, like glass or air, it has a LOWER SPEED than in a vacuum; the ratio of c to this slower speed is called the refractive index of the medium. Changes of gravity, however, warp the space the light has to travel through, making it appear to curve around massive objects. This gives rise to the phenomenon of gravitational lensing, in which large assemblies of matter can refract light from far away sources, so as to produce multiple images and similar optical distortions.

Answer 2

Yes we are.

Totally and completely positive.

Leaving out for the moment those reactions where gasses or other translucent materials are used to specifically slow down photons, Yes, it is an absolute.

There have been numerous experiments to prove Einsteins theory of special reltivity. It has been proven without a doubt to be the true theory.

Often times people will use the the logical fallacy of "Proof by Example" to say that because it was once thought that the Speed of Sound could not be broken that the Speed of Light will fall as well; this is absurd. C (or The Speed of Light in a vacuum) is an inertially independent absolute.

What do we really mean by this? Let's use the classic example of the Train - its an express, so it's not going to stop at the station where you are, it's going to whiz right through. On top of the train is El Bandito, and his trusty laser cannon. The train is going .9999999C - in other words a fraction of a gnats butt hair slower than lightspeed itself. When the Train, with El Bandito on top of it, is 100K away from you, El Bandito turns on his ultra-powerful laser, pointing it directly at you. How long does it take for the light to reach you. As a human, we intuitively add the velocities together. We do this because we evolved as co-operative hunters and we can do amazingly accurate throw/catch calculations in our head - which allows us to throw and catch. Back to El Bandito... He's 100K away when he switches on the Laser, how long to get to you? Well C is 299792458 M/ps and he was 100K away so it only took the light .000334 seconds, or so to get to you. Now, you say, why doesn't the great speed of the train have to be taken into account - well it does, but it comes out the side - just like when you bite down into a juicy cheesburger and half the insides squuirt out the side, the great speed of the train and El Bandito has to do something to the light being beamed from his laser to you, right?

It does. All that speed the train has changes the wavelength of the Laser. There is a long drawn-out way to explain the differences, but essentially since the train is rushing at you it compresses the wavelength (blue shifting) and once the Train passes you, if El Bandito were to shoot at you again, it would be red (uncompressing the wavelength, as the train rushes away from you).

That's how we know it's an absoulte everywhere. It has to be. We have observed this (red/blue shift) happening to a great deal of the universe. We know it's true.

Answer 3

Einstein answered that with his special theory of relativity. That the speed that light travels even in the vaccum of space is constant and no none cannot travel faster that the speed of light. They can travel colse to it, but not faster than light. And as for a black hole, The gravity is so extreme that it makes ligt bend before falling into it.

Answer 4

It doesn't travel at the same speed everywhere on Earth. Are you familiar with a material characteristic called 'refractive index'? If not, you should be.

But electromagnetic radiation travelling in a vacuum does appear to travel at the same velocity with respect ot any inertial reference frame (althouigh it's wavelength may change)


Doug

Answer 5

It doesn't. It slows down when passing through a medium of refractive index greater than 1.

Answer 6

People were once positive that the Earth was flat. Who knows?

Answer 7

Not precisely positive, but pretty sure. There is plenty of evidence that it is and none that it isn't.

Answer 8

i think it does. but thereis no way to be sure. we've never been anywhere else!

Answer 9

its gotta be