# Faster than Light data possible??

• November 9th, 2005, 05:22 AM
daveyjones
Faster Than Light Data Streams?
Hi,

I read that using Plasmas, the phase velocity of an em wave can be increased instead of decreased as in normal materials.

http://www.rmcybernetics.com/science..._materials.htm

Does this mean that you could send data faster than the speed of light? Or does this defy special relativity?

Cheers,
DaveyJones
• November 9th, 2005, 08:56 AM
silylene
You can't go faster than the speed of light in the medium.

But the speed of light does vary with the refractive index of the medium the light is traveling through.

n = c / v where n = ref index of the medium, c = speed of light in a vacuum, v = speed of light in that medium

In a vacuum, n=1. For air, n = 1.0004

It is possible to have materials with n <1 for certain wavelengths, through a phenomena known as anomalous dispersion. In this case, if n = 0.5 for certain wavelengths, then light of that wavelength travels through that material faster than it would in a vacuum. Unfortunately, materials with n<1 are not transparent, so the light doesn't travel very far!

Here are some good articles to read:
Theory of refraction: http://theory.uwinnipeg.ca/physics/light/node5.html

Theory of dispersion, with some discussion of 'apparent' possibility of superluminal communication: http://en.wikipedia.org/wiki/Dispersion_
(optics)

Discussion from PhysicsWorld of how nothing goes faster than light: http://physicsweb.org/articles/world/13/9/3

If you get real curious, google "negative refractive index". There are some very interesting developments in this concept in the last decade, with strange results.
• November 10th, 2005, 01:07 AM
wallaby
well if its over short distances wouldn't the message be recieved before it is sent.
• November 10th, 2005, 01:20 AM
mitchellmckain
Re: Faster than Light data possible??
Quote:

Originally Posted by daveyjones
Hi,

I read that using Plasmas, the phase velocity of an em wave can be increased instead of decreased as in normal materials.

http://www.rmcybernetics.com/science..._materials.htm

Does this mean that you could send data faster than the speed of light? Or does this defy special relativity?

Cheers,
DaveyJones

This is periodically challenged by new phenomena like this all the time. The possibility that it could be faster than light is discussed only because it creates a sensation in the media and gets people to pay attention. But when other scientists check up on this possibility they invariably find that the information travels less than the speed of light.

Here is an example which was discussed in a thread under "Astronomy and Cosmology".
www.npl.washington.edu/av/altfw75.html