Relativity and the Laser Beam: Is Faster-Than-Light Travel Possible?

In summary, according to this scientist, by shooting a laser beam through a high density gas, they were able to break the speed of light in that gas. This is because they were able to send a superposition (sum) of waves through the gas that moved faster than the speed of light in a vacuum.
  • #1
Cosmo16
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I saw this awhile ago, I don't remember where though.

Supposdly some scientists accelereted the beam of a laser faster then the speed of light, by shooting it through a high density gas. The opinion being that Relativity only states that nothing can go faster then the speed of light in a vaccum. is this a vaild conclusion? I don't know enough about relativity to know for myself, but it seems like a valid conclusion to me.
 
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  • #2
Cosmo16 said:
I saw this awhile ago, I don't remember where though.
Supposdly some scientists accelereted the beam of a laser faster then the speed of light, by shooting it through a high density gas. The opinion being that Relativity only states that nothing can go faster then the speed of light in a vaccum. is this a vaild conclusion? I don't know enough about relativity to know for myself, but it seems like a valid conclusion to me.
I'm just guessing, but I think what happened was that a particle, perhaps an electron, was accelerated in a gas to a velocity that was less than the speed of light in vacuum, but greater than the speed of light in that gas. Such speeds are achieved routinely and are the source of a phenomenon known as Chernenkov radiation.

However as you have worded it, it sounds like it was a laser beam and not a particle that was shot. I can't guess what is meant by light traveling faster than light.
 
  • #3
A superposition (sum) of waves was sent through a medium such that the group velocity (Yes, group velocity!) of the resulting wave packet moved faster than the speed of light in a vacuum. Greg Egan has a nice animation of this http://gregegan.customer.netspace.net.au/APPLETS/20/20.html" [Broken].

From Egan's webpage: "Nothing is actually traveling with these peaks, though; they're just an artifact of the way the different frequencies are slipping in and out of phase."

Don't hesitate to come back if you have questions.

Regards,
George
 
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  • #4
What does he mean by "the way the different frequencies are slipping in and out of phase"

P.S. Thanks for the link, the animation helped.
 
  • #5
Two waves are completely in phase if their crests line up or if their troughs line up, and completely out of phase if the crests in one wave line up with the troughs in the other. When waves are in phase, they tend to reinforce each other; when waves are out of phase, they tend to cancel each other.

In the animation, two effects have to be taken into account: 1) different colours have different wavelengths; 2) different colours move at different speeds.

The reason for 2) is as follows. The index of refraction of a medium is defined as the ratio of the speed of light in a vacuum to the (effective) speed of light in the medium, i.e., n = c/v. Thus, v = c/n. In what is called a dispersive medium, the index of refraction is slightly different for different colours of light. Since n depends on colour and c is constant, v depends on colour.

The combination of 1) and 2) above cause the different colours to slip in and out of phase.

Regards,
George
 

1. What is relativity and how does it relate to faster-than-light travel?

Relativity is a theory developed by Albert Einstein that explains the relationship between space and time. It states that the laws of physics are the same for all observers, regardless of their relative motion. This theory is important in understanding the possibility of faster-than-light travel because it sets the limit of the speed of light as the maximum speed at which any object can travel.

2. Can a laser beam be used to achieve faster-than-light travel?

No, a laser beam cannot be used for faster-than-light travel. While lasers are able to travel at incredibly high speeds, they are still limited by the speed of light. Additionally, the energy required to accelerate an object to the speed of light would be nearly infinite.

3. Are there any known examples of faster-than-light travel?

No, there are no known examples of objects or particles traveling faster than the speed of light. While some experiments have shown particles appearing to travel faster than light, these results have been attributed to experimental error and have not been replicated.

4. Is it possible to bend space and time to achieve faster-than-light travel?

The theory of relativity does allow for the possibility of bending space and time, also known as warping spacetime. However, this would require an immense amount of energy and technology that is currently beyond our capabilities. Additionally, it is still subject to the speed of light limit.

5. Could there be other ways to achieve faster-than-light travel?

While there are currently no known ways to travel faster than the speed of light, some scientists have proposed the concept of wormholes or shortcuts through spacetime that could potentially allow for faster travel. However, this is still purely theoretical and would require advanced technology and understanding of the laws of physics that we currently do not possess.

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