3 ms·

>Expansion means that two points in space can be moving apart at greater than the speed of light - but that's not the same thing as traveling faster than the sp

>Expansion means that two points in space can be moving apart at greater than the speed of light - but that's not the same thing as traveling faster than the speed of light. It actually is and that is exactly the mechanism behind the Alcubierre drive mentioned in the post. But that doesn't change the fact that compressing and expanding space on practical scales is an astronomically difficult problem and we don't even have the slightest clue what the gravitational wave signal of the technology would look like. It's also unlikely that we could even measure it for the scenario outlined where mass just disappears and appears, unless these ships have masses of several suns.

ggeorgovassilis 3y ago
> It's also unlikely that we could even measure it for the scenario outlined I understand the LIGO data is available. A skilled data analyst could look at it and tell if it's possible or not. If aliens FTL around our neighbourhood, maybe it does show up?
- sigmoid10 3y ago
  A skilled data analyst would never even attempt that before having a very strong theoretical model for the kind of signal they are looking for. Otherwise you could end up with countless "discoveries" that in reality are just statistical noise. LIGO's discoveries were only possible because of decades of theoretical research in General Relativity and simulations of black hole dynamics. They already knew precisely what the signal would look like before they ever saw it.
  - ggeorgovassilis 3y ago
    > A skilled data analyst would never even attempt that before having a very strong theoretical model I know for a fact this generalisation to be false
    - sigmoid10 3y ago
      Then I guess we disagree on the definition of "skilled." What I'm trying to say is you definitely won't find something like that published by the LIGO collaboration or other serious astronomers.
fnordpiglet 3y ago
Space seems to expand in the absence of anything, and mass and its agent gravity appear to counteract that natural expansion of distance. If this is in fact true, I don’t think it’s astronomically hard but impossible to directly manipulate space. Space isn’t actually a thing to be manipulated, it’s a description of the apparent distance between things of reference. The discussion of space warping around mass etc is a convenient metaphor for what we observe, the bowling ball on a blanket doesn’t mean there’s literally a blanket to be manipulated. It’s an effect we observe about relative distances being distorted in the metrics of distance and rate of information propagation. What medium these exist in, if any, is entirely unknown and is most likely non existent but is a description of observed effects, while space and time are simply descriptions of those effects.
- sigmoid10 3y ago
  This is wrong. General Relativity tells us exactly how mass (or rather energy) affects spacetime. This has nothing to do with relative distances. The issue with wormholes and warp drives in general relativity is that they require weird forms of energy that we know exist in quantum mechanics, but may not work on macroscopic scales.

ggeorgovassilis 3y ago

> It's also unlikely that we could even measure it for the scenario outlined I understand the LIGO data is available. A skilled data analyst could look at it and tell if it's possible or not. If aliens FTL around our neighbourhood, maybe it does show up?

sigmoid10 3y ago
A skilled data analyst would never even attempt that before having a very strong theoretical model for the kind of signal they are looking for. Otherwise you could end up with countless "discoveries" that in reality are just statistical noise. LIGO's discoveries were only possible because of decades of theoretical research in General Relativity and simulations of black hole dynamics. They already knew precisely what the signal would look like before they ever saw it.
- ggeorgovassilis 3y ago
  > A skilled data analyst would never even attempt that before having a very strong theoretical model I know for a fact this generalisation to be false
  - sigmoid10 3y ago
    Then I guess we disagree on the definition of "skilled." What I'm trying to say is you definitely won't find something like that published by the LIGO collaboration or other serious astronomers.

fnordpiglet 3y ago

Space seems to expand in the absence of anything, and mass and its agent gravity appear to counteract that natural expansion of distance. If this is in fact true, I don’t think it’s astronomically hard but impossible to directly manipulate space. Space isn’t actually a thing to be manipulated, it’s a description of the apparent distance between things of reference. The discussion of space warping around mass etc is a convenient metaphor for what we observe, the bowling ball on a blanket doesn’t mean there’s literally a blanket to be manipulated. It’s an effect we observe about relative distances being distorted in the metrics of distance and rate of information propagation. What medium these exist in, if any, is entirely unknown and is most likely non existent but is a description of observed effects, while space and time are simply descriptions of those effects.

sigmoid10 3y ago
This is wrong. General Relativity tells us exactly how mass (or rather energy) affects spacetime. This has nothing to do with relative distances. The issue with wormholes and warp drives in general relativity is that they require weird forms of energy that we know exist in quantum mechanics, but may not work on macroscopic scales.