4 ms·

Warp speed travel is theoretically possible, says astrophysicist

6 points by chris-at 11y ago

zamalek 11y ago
Interestingly a short while back White's lab did notice a statistically relevant effect regarding one of their candidate warping devices. However, they aren't ready to make any conclusions about the effect that they saw - so far as I understand it's merely a very weak correlation right now. Something interesting, but nobody should get their hopes up. Either way I seriously recommend some thorough Googling about this subject as that article is unbelievably out of date. I play Elite: Dangerous once in a while and one thing that game really teaches you is that even 'c' is really slow in astronomical terms. You start to realize that for space colonization to become truly viable we'd have to hope for some real analog of "hyperspace," as "warp" simply won't cut it in the long run.
- w0000t 11y ago
  Well that is clearly not true. Thanks to relativity, colonization is very possible in a short time span.
  - zamalek 11y ago
    > relativity Good point. Let me rephrase that: a long time from the perspective of the people doing the colonization :)
    - w0000t 11y ago
      If by those you mean people who are actually traveling in the star-ships, then it is a short time. It is only a long time for people staying stationary relative to the travelers.
      - zamalek 11y ago
        Am I severely misunderstanding something? Doesn't the warp drive move the ship at e.g. 20c according to the ship's frame of reference? Given that, at 20c it would take the inhabitants of the ship 53 days to reach Alpha Centauri (4 light years). Multiply that by 18000 for the other side of the galaxy (72000 light years): 261 years. You most likely couldn't make that in "one hop" so you'd have some crazy multiplier depending on the maximum travel distance of your drive. Even if you didn't want to travel colonize the other size of the galaxy you'd have to search some 400 billion stars for a habitable planet. That's what I'm saying: once you move past the "local neighborhood" things become quite ridiculous.
        w0000t 11y ago
        I was referring to sub c speeds and what happens by using real confirmed physics. I didn't realize you were talking about warp drives in that case. As far as I understand from popular science, warp drive doesn't actually move the occupants of the vehicle, it moves the space around the ship so in that case there is no time dilation. It takes the same amount of time for people, in and outside, the ship. If your warp drive is limited to 20c then yes it is a problem, but I don't see why would it have to be limited in the first place. Make it go 10^10c and the problem is solved.
        zamalek 11y ago
        > I was referring to sub c speeds and what happens by using real confirmed physics. That much so much more sense. In addition to the velocity there would also be time spent completely outside of a gravity well. However, the article is really talking about warp. > Make it go 10^10c and the problem is solved. Too much energy. From what I understand it's exponential - i.e. more energy would be used getting to Alpha Centauri at 10^10c than at 20c. We don't know exactly how to get to 1c in the first place, but we do know that if we could then e.g. 100c would likely be something that would be out of reach. Keep in mind that before White optimized the Alcubierre metric, getting to Pluto (AFAIR) with a warp drive would have required the mass of Jupiter. Getting to Alpha Centauri would have required the mass of the observable universe (which is now down to something with "the mass of Voyager 1"). That's the amount of energy we are talking about even at a pitiful 20c.
rootbear 11y ago
The article is badly edited, speaking of both "negative density energy" and "negative energy density", when the latter is what was meant. Even though, as I understand it, General Relativity doesn't forbid FTL explicitly, it doesn't get you out of the causality problems of FTL. At least, I've never seen an explanation of a "warp" style FTL method that doesn't allow for causality violation. I'm all ears, if someone wants to convince me that warp drives can't violate causality.
- w0000t 11y ago
  You assume that warp drive actually moves you trough space, it doesn't. Problem solved. Here is a practical example: I decide to travel to Alpha Centauri, and I'm there. Time passed for everybody is the same. You cannot cause any problems. Note that you are not allowed to change reference frames, by doing this. This does sound illogical, since you move to some other location, but if you assume you didn't move, like we did, then it isn't. Actually the space moved, and that might cause some other problems we don't know about.
  - drdeca 11y ago
    I think the alcubierre drive still violates causality if you go ftl. Iirc, the ftl violates causality thing isn't from going faster than light, but rather because where you end up is outside of the future light cone of where you started. It's also, I think, outside of your past light cone, so a single ftl trip in a straight line might not have retrocausality, but because the region outside of both the past and future light comes can be considered to be either before or after the start timeplace, by choosing a different reference frame, if you have two ftl trips, that is enough for causing past events. I think this doesn't matter what happens during the trips, just the start and end timeplaces.
    - w0000t 11y ago
      The light cone only matters if you actually move. The accepted idioms from relativity don't apply here. I think we are just not talking about the same "warp" drive. The version that doesn't violate causality works like this. You are not allowed to accelerate( using normal rockets ) to near c velocity and then warp to a stop to some distant location. This would cause problems. Instead you will end up there with all of your accumulated velocity before the warp. Then you have to come to a stop the same way you accelerated. In other words, warp will change your location but not your velocity in spacetime.

6 points by chris-at 11y ago

Interestingly a short while back White's lab did notice a statistically relevant effect regarding one of their candidate warping devices. However, they aren't ready to make any conclusions about the effect that they saw - so far as I understand it's merely a very weak correlation right now. Something interesting, but nobody should get their hopes up. Either way I seriously recommend some thorough Googling about this subject as that article is unbelievably out of date. I play Elite: Dangerous once in a while and one thing that game really teaches you is that even 'c' is really slow in astronomical terms. You start to realize that for space colonization to become truly viable we'd have to hope for some real analog of "hyperspace," as "warp" simply won't cut it in the long run.

w0000t 11y ago
Well that is clearly not true. Thanks to relativity, colonization is very possible in a short time span.
- zamalek 11y ago
  > relativity Good point. Let me rephrase that: a long time from the perspective of the people doing the colonization :)
  - w0000t 11y ago
    If by those you mean people who are actually traveling in the star-ships, then it is a short time. It is only a long time for people staying stationary relative to the travelers.
    - zamalek 11y ago
      Am I severely misunderstanding something? Doesn't the warp drive move the ship at e.g. 20c according to the ship's frame of reference? Given that, at 20c it would take the inhabitants of the ship 53 days to reach Alpha Centauri (4 light years). Multiply that by 18000 for the other side of the galaxy (72000 light years): 261 years. You most likely couldn't make that in "one hop" so you'd have some crazy multiplier depending on the maximum travel distance of your drive. Even if you didn't want to travel colonize the other size of the galaxy you'd have to search some 400 billion stars for a habitable planet. That's what I'm saying: once you move past the "local neighborhood" things become quite ridiculous.
      - w0000t 11y ago
        I was referring to sub c speeds and what happens by using real confirmed physics. I didn't realize you were talking about warp drives in that case. As far as I understand from popular science, warp drive doesn't actually move the occupants of the vehicle, it moves the space around the ship so in that case there is no time dilation. It takes the same amount of time for people, in and outside, the ship. If your warp drive is limited to 20c then yes it is a problem, but I don't see why would it have to be limited in the first place. Make it go 10^10c and the problem is solved.
        zamalek 11y ago
        > I was referring to sub c speeds and what happens by using real confirmed physics. That much so much more sense. In addition to the velocity there would also be time spent completely outside of a gravity well. However, the article is really talking about warp. > Make it go 10^10c and the problem is solved. Too much energy. From what I understand it's exponential - i.e. more energy would be used getting to Alpha Centauri at 10^10c than at 20c. We don't know exactly how to get to 1c in the first place, but we do know that if we could then e.g. 100c would likely be something that would be out of reach. Keep in mind that before White optimized the Alcubierre metric, getting to Pluto (AFAIR) with a warp drive would have required the mass of Jupiter. Getting to Alpha Centauri would have required the mass of the observable universe (which is now down to something with "the mass of Voyager 1"). That's the amount of energy we are talking about even at a pitiful 20c.

rootbear 11y ago

The article is badly edited, speaking of both "negative density energy" and "negative energy density", when the latter is what was meant. Even though, as I understand it, General Relativity doesn't forbid FTL explicitly, it doesn't get you out of the causality problems of FTL. At least, I've never seen an explanation of a "warp" style FTL method that doesn't allow for causality violation. I'm all ears, if someone wants to convince me that warp drives can't violate causality.

w0000t 11y ago
You assume that warp drive actually moves you trough space, it doesn't. Problem solved. Here is a practical example: I decide to travel to Alpha Centauri, and I'm there. Time passed for everybody is the same. You cannot cause any problems. Note that you are not allowed to change reference frames, by doing this. This does sound illogical, since you move to some other location, but if you assume you didn't move, like we did, then it isn't. Actually the space moved, and that might cause some other problems we don't know about.
- drdeca 11y ago
  I think the alcubierre drive still violates causality if you go ftl. Iirc, the ftl violates causality thing isn't from going faster than light, but rather because where you end up is outside of the future light cone of where you started. It's also, I think, outside of your past light cone, so a single ftl trip in a straight line might not have retrocausality, but because the region outside of both the past and future light comes can be considered to be either before or after the start timeplace, by choosing a different reference frame, if you have two ftl trips, that is enough for causing past events. I think this doesn't matter what happens during the trips, just the start and end timeplaces.
  - w0000t 11y ago
    The light cone only matters if you actually move. The accepted idioms from relativity don't apply here. I think we are just not talking about the same "warp" drive. The version that doesn't violate causality works like this. You are not allowed to accelerate( using normal rockets ) to near c velocity and then warp to a stop to some distant location. This would cause problems. Instead you will end up there with all of your accumulated velocity before the warp. Then you have to come to a stop the same way you accelerated. In other words, warp will change your location but not your velocity in spacetime.