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To: Talisker

Okay, let’s get special relativity right: in the vacuum, massless particles (like light) travel at the speed of light; massive particles (or macroscopic objects made of such) cannot be accelerated to the speed of light due to the Lorentz shift in mass, which would mean an infinite amount of energy would be needed to accelerate them to the speed of light.

As to superluminal travel, in the sense of ordinary motion through space, it is forbidden by special relativity.

What is not forbidden by the theory are dodges like warp drives and stable wormholes. In fact there are solutions to Einstein’s equations (general relativity) which allow both—one solution is called “the Alcubier warp drive” because a body in one region of space-time in that solution looks like a warp-driven starship to the rest of the universe.

Unfortunately, all of these exotic solutions require there to be regions of space-time with negative mass-energy density. Negative energy densities have been observed, but only at the level of quantum fluctuations in the presence of equal nearby positive energy densities (if they tunneled out of the vacuum, or larger positive energy densities if some process was used to create a negative energy density).

There seems to be no way to collect lots of negative energy in one place to make either a warp drive or a stable wormhole. (Incidentally the amount of negative mass-energy
needed to make a wormhole big enough to walk through and keep it open is about minus the mass of Jupiter. I’m not sure the estimates on the Alcubier warp drive.)


28 posted on 09/29/2010 8:10:17 PM PDT by The_Reader_David (And when they behead your own people in the wars which are to come, then you will know. . .)
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To: The_Reader_David
Okay, let’s get special relativity right: in the vacuum, massless particles (like light) travel at the speed of light;
massive particles (or macroscopic objects made of such) cannot be accelerated to the speed of light due to the Lorentz shift in mass, which would mean an infinite amount of energy would be needed to accelerate them to the speed of light.

As to superluminal travel, in the sense of ordinary motion through space, it is forbidden by special relativity.
What is not forbidden by the theory are dodges like warp drives and stable wormholes.
In fact there are solutions to Einstein’s equations (general relativity) which allow both—one solution is called “the Alcubier warp drive” because a body in one region of space-time in that solution looks like a warp-driven starship to the rest of the universe.

Unfortunately, all of these exotic solutions require there to be regions of space-time with negative mass-energy density.
Negative energy densities have been observed, but only at the level of quantum fluctuations in the presence of equal nearby positive energy densities (if they tunneled out of the vacuum, or larger positive energy densities if some process was used to create a negative energy density).

There seems to be no way to collect lots of negative energy in one place to make either a warp drive or a stable wormhole.
(Incidentally the amount of negative mass-energy needed to make a wormhole big enough to walk through and keep it open is about minus the mass of Jupiter.
I’m not sure the estimates on the Alcubier warp drive.)
<--- YEA .. What He Said!
38 posted on 09/29/2010 8:19:42 PM PDT by plinyelder ("I've noticed that everybody that is for abortion has already been born." -- Ronald Reagan)
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