4 ms·

Some of your observations are good, for those I thank you, and revised the post accordingly. > I wish the article justified this statement Your wish has been

Some of your observations are good, for those I thank you, and revised the post accordingly. > I wish the article justified this statement Your wish has been granted. Also, it's in the referenced Wikipedia article: "galaxies that are farther than the Hubble radius, approximately 4.5 gigaparsecs or 14.7 billion light-years, away from us have a recession speed that is faster than the speed of light". > that's not the same thing as traveling faster than the speed of light. The mechanism seems different, so indeed not the same thing, but the result seems to be the same. > it doesn't explain why FTL would look like teleportation The proposed detection method is agnostic towards what happens during the trip, it focusses on detecting the initial and terminal event - a mass disappearing (rapidly) from one point and re-appearing (rapidly) at another. That probably wouldn't work if FTL travel produces significant gravitational distortions, in which case we're lucky because that would stick out as a signal. It also wouldn't work if the FTL drive involves long phases of acceleration and deceleration.

pavel_lishin 3y ago
> the result seems to be the same. I don't ... think that's true, but I'd have to think about this some more. The distance between two objects increasing at a speed greater than light is not the same thing as an object traveling - that is, traversing space - faster than the speed of light. To put it more specifically, the expansion of space doesn't help whatsoever get you from Point of Interest A to Point of Interest B faster than light can get there. (If you can compress space - the Alcubierre drive has been mentioned - then that may not be true, but that's not the same thing as the expansion of space, I don't think.) > it focusses on detecting the initial and terminal event - a mass disappearing (rapidly) from one point and re-appearing (rapidly) at another. I'm still not convinced that this is what FTL travel would look like to an external observer. I don't think you've done enough to justify this assertion.
- ggeorgovassilis 3y ago
  > I'm still not convinced that this is what FTL travel would look like to an external observer. I'm not either, I'm saying that if that's the case, there is an easy way to find out. > I don't think you've done enough to justify this assertion. Again, speculation, not assertion. The proposed detection mechanism works only in the described case.
- ithkuil 3y ago
  Yeah. Expanding space behind you may effectively allow you to recede from the origin point at arbitrary speeds but that doesn't imply you'll get any closer to your destination. Unless you're also able to compress the space ahead of you (which is what an alcubierre drive would do). You wouldn't be moving through space at all. Your destination would be closer. Arbitrarily closer. Eventually you'll then just reach the destination as if you moved. Now, I'm quite skeptical about the whole idea but I have to admit I didn't do the math. Wm
- torginus 3y ago
  This just made me think of something - would it be accurate to say that the speed of light is getting slower over time, when measured over insterstellar distances? Speed is distance over time, and distance is measured by a landmark in this case. In a hypothetical world where an observer has only a distant pointlike object as reference, and he measures that the time it takes for light to arrive from the object, would it not be equally valid for them to assume that the distance is increasing, or the speed of light is decreasing? Would it be possible to say that light suffers from 'drag' over large distances thereby further objects appearing to take even longer to get to than it would be proportional?

pavel_lishin 3y ago

> the result seems to be the same. I don't ... think that's true, but I'd have to think about this some more. The distance between two objects increasing at a speed greater than light is not the same thing as an object traveling - that is, traversing space - faster than the speed of light. To put it more specifically, the expansion of space doesn't help whatsoever get you from Point of Interest A to Point of Interest B faster than light can get there. (If you can compress space - the Alcubierre drive has been mentioned - then that may not be true, but that's not the same thing as the expansion of space, I don't think.) > it focusses on detecting the initial and terminal event - a mass disappearing (rapidly) from one point and re-appearing (rapidly) at another. I'm still not convinced that this is what FTL travel would look like to an external observer. I don't think you've done enough to justify this assertion.

ggeorgovassilis 3y ago
> I'm still not convinced that this is what FTL travel would look like to an external observer. I'm not either, I'm saying that if that's the case, there is an easy way to find out. > I don't think you've done enough to justify this assertion. Again, speculation, not assertion. The proposed detection mechanism works only in the described case.
ithkuil 3y ago
Yeah. Expanding space behind you may effectively allow you to recede from the origin point at arbitrary speeds but that doesn't imply you'll get any closer to your destination. Unless you're also able to compress the space ahead of you (which is what an alcubierre drive would do). You wouldn't be moving through space at all. Your destination would be closer. Arbitrarily closer. Eventually you'll then just reach the destination as if you moved. Now, I'm quite skeptical about the whole idea but I have to admit I didn't do the math. Wm
torginus 3y ago
This just made me think of something - would it be accurate to say that the speed of light is getting slower over time, when measured over insterstellar distances? Speed is distance over time, and distance is measured by a landmark in this case. In a hypothetical world where an observer has only a distant pointlike object as reference, and he measures that the time it takes for light to arrive from the object, would it not be equally valid for them to assume that the distance is increasing, or the speed of light is decreasing? Would it be possible to say that light suffers from 'drag' over large distances thereby further objects appearing to take even longer to get to than it would be proportional?