Faster-Than-Light Travel/Analysis: Difference between revisions

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In real space, even approaching lightspeed would require more energy per second than all of Earth's industries use per year. While this may be [[Hand Wave|explained]] by advances in technology, the general formulas for velocity and acceleration are such that as you approach the speed of light, the energy needed to accelerate anything with non-zero mass increases asymptotically. In other words, you need an ''infinite'' amount of energy (and an ''infinite'' amount of time) to accelerate to the speed of light.
In real space, even approaching lightspeed would require more energy per second than all of Earth's industries use per year. While this may be [[Hand Wave|explained]] by advances in technology, the general formulas for velocity and acceleration are such that as you approach the speed of light, the energy needed to accelerate anything with non-zero mass increases asymptotically. In other words, you need an ''infinite'' amount of energy (and an ''infinite'' amount of time) to accelerate to the speed of light.


Additionally, Albert Einstein's well-supported [[Useful Notes/Relativity|Special Relativity]] theory holds that FTL travel simply ''cannot'' work, by the fundamental laws of physics. Due to the space-time distortion at relativistic speeds, [[Ludicrous Speed|it would imply violations of causality itself!]] For example, a superluminal signal sent from A to B will appear, in another reference frame, [http://www.theculture.org/rich/sharpblue/archives/000089.html to be received ''before'' being sent]. This is the reason why some say that FTL travel implies time travel -- but that is sloppy language. What ''actually'' happens is that causality is thrown out of whack, and that different observers don't always agree whether effects precede their causes or not. In effect, this means that, in special relativity, going faster than light is impossible -- with or without time travel. In Einstein's much more comprehensive theory of ''General'' Relativity, however, matters are considerably more complex, and FTL travel ''is not known'' to necessarily imply causality violations (see [[Real Life]] examples below)... But, all in all, suffice it to say that having the protagonists' rocketship outrun a beam of light will always require some serious [[Hand Wave|hand waving]] by the author.<ref>It should be noted that in relativistic physics it ''is'' possible to get arbitrarily far within an arbitrarily short time ''from the perspective of the person doing the moving''. Time itself is relative, and stationary observers see the flow of time for the person traveling ''slow down'', so that in the time it takes the traveler to get to their destination, he or she experiences less time passing than the stationary observers do. The person making the journey sees the distance to their destination contracted along their direction of travel, so they have less distance to cover than they did when they were stationary. This makes it ''theoretically'' possible for an astronaut to cross great distances in a single life-time, but FTL travel is still required if you don't want the journey to take eons from the perspective of those the traveler left behind on Earth.</ref> See also [[Time Dilation]].
Additionally, Albert Einstein's well-supported [[Relativity|Special Relativity]] theory holds that FTL travel simply ''cannot'' work, by the fundamental laws of physics. Due to the space-time distortion at relativistic speeds, [[Ludicrous Speed|it would imply violations of causality itself!]] For example, a superluminal signal sent from A to B will appear, in another reference frame, [http://www.theculture.org/rich/sharpblue/archives/000089.html to be received ''before'' being sent]. This is the reason why some say that FTL travel implies time travel -- but that is sloppy language. What ''actually'' happens is that causality is thrown out of whack, and that different observers don't always agree whether effects precede their causes or not. In effect, this means that, in special relativity, going faster than light is impossible -- with or without time travel. In Einstein's much more comprehensive theory of ''General'' Relativity, however, matters are considerably more complex, and FTL travel ''is not known'' to necessarily imply causality violations (see [[Real Life]] examples below)... But, all in all, suffice it to say that having the protagonists' rocketship outrun a beam of light will always require some serious [[Hand Wave|hand waving]] by the author.<ref>It should be noted that in relativistic physics it ''is'' possible to get arbitrarily far within an arbitrarily short time ''from the perspective of the person doing the moving''. Time itself is relative, and stationary observers see the flow of time for the person traveling ''slow down'', so that in the time it takes the traveler to get to their destination, he or she experiences less time passing than the stationary observers do. The person making the journey sees the distance to their destination contracted along their direction of travel, so they have less distance to cover than they did when they were stationary. This makes it ''theoretically'' possible for an astronaut to cross great distances in a single life-time, but FTL travel is still required if you don't want the journey to take eons from the perspective of those the traveler left behind on Earth.</ref> See also [[Time Dilation]].


Even outside of Einstein's flavor of Relativity <ref>Not only because it got [[Real Life]] physics issues of its own. It's ''already'' thrown away if the 'verse in question has "gravitons" or "antigravity".</ref>, other theories tend to impose limitations just as strict. Note that once the gravity is not the same as spatial anomalies, it's likely to be affected by them -- which may be bad news for massive objects close to even-more-massive objects.
Even outside of Einstein's flavor of Relativity <ref>Not only because it got [[Real Life]] physics issues of its own. It's ''already'' thrown away if the 'verse in question has "gravitons" or "antigravity".</ref>, other theories tend to impose limitations just as strict. Note that once the gravity is not the same as spatial anomalies, it's likely to be affected by them -- which may be bad news for massive objects close to even-more-massive objects.
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