3 ms·

What’s the argument for warp drive not violating causality? (She mentions she explains it in another video but I couldn’t find it.)

jleahy 6y ago
The argument is that they're impossible, because they require negative energy (which not only doesn't exist but doesn't make sense), so it's fine. In the presence of negative energy you can form closed time-like curves in general relativity, which would violate causality, but these are not valid solutions because negative energy is not a thing. It's just like saying you can travel faster than the speed of light in special relativity, you just need imaginary mass (ie. m^2<0), but mass is unfortunately a real quantity rather than a complex quantity so you can't.
- mrfusion 6y ago
  Isn’t this artical saying you don’t need negative energy?
  - jleahy 6y ago
    No, faster than light needs negative energies.
sgt101 6y ago
Causality violation is an observation of physics.. not a law !
- scarygliders 6y ago
  The way I think of it is this; If it's NOW in the Sol system, it's NOW in Alpha Centauri as well. (I guess it's difficult to think in these terms because we always only see a 4.367 years old "NOW" from Alpha Centauri.) There would be no violation of Causality if you had a ship which could instantly Jump between Sol and Alpha Centauri - you'd simply arrive there at NOW+<however long this Jump took> - whether it's seconds or picoseconds. If you sent a radio signal "Hi there!" from Sol to Alpha Centauri before this Jump, you'd be waiting for 4.367 years for it to arrive - which still isn't a violation of Causality, because it'd be NOW+4.367 years in Alpha Centauri and the same would be true in the Sol system. If your faster-than-light (faster-than-Causality) Drive wasn't an instantaneous Jump like above, Causality is still not violated, because you'd still be arriving at NOW + <however long it took> to travel between Sol & Alpha Centauri. Maybe you could only travel at twice the speed of light (twice the speed of Causality), in which case you'd arrive there in NOW + 2.1835 years
  - davrosthedalek 6y ago
    The problem with this is that there is now an unaccelerated, moving (with relation to here/Alpha Centauri) system in which you appear in AC before you leave here, i.e. break causality.
    - scarygliders 6y ago
      No, there really isn't, and my post explained precisely why.
    - mrfusion 6y ago
      But that system would see a strange thing but it wouldn’t be sending information backwards because they wouldn’t be able to act on that information on earth or AC. Maybe it’s the same as how I can move a beam of light across the moon faster than light but that’s ok since it can’t send information. Am I misunderstanding it?
  - lalaithion 6y ago
    This is not our current understanding of Physics.
    - scarygliders 6y ago
      Please elaborate.
  - Dylan16807 6y ago
    That's called having a privileged reference frame, and yes, if your FTL jumps all use the same reference frame then there's no way to violate causality.

jleahy 6y ago

The argument is that they're impossible, because they require negative energy (which not only doesn't exist but doesn't make sense), so it's fine. In the presence of negative energy you can form closed time-like curves in general relativity, which would violate causality, but these are not valid solutions because negative energy is not a thing. It's just like saying you can travel faster than the speed of light in special relativity, you just need imaginary mass (ie. m^2<0), but mass is unfortunately a real quantity rather than a complex quantity so you can't.

mrfusion 6y ago
Isn’t this artical saying you don’t need negative energy?
- jleahy 6y ago
  No, faster than light needs negative energies.

sgt101 6y ago

Causality violation is an observation of physics.. not a law !

scarygliders 6y ago
The way I think of it is this; If it's NOW in the Sol system, it's NOW in Alpha Centauri as well. (I guess it's difficult to think in these terms because we always only see a 4.367 years old "NOW" from Alpha Centauri.) There would be no violation of Causality if you had a ship which could instantly Jump between Sol and Alpha Centauri - you'd simply arrive there at NOW+<however long this Jump took> - whether it's seconds or picoseconds. If you sent a radio signal "Hi there!" from Sol to Alpha Centauri before this Jump, you'd be waiting for 4.367 years for it to arrive - which still isn't a violation of Causality, because it'd be NOW+4.367 years in Alpha Centauri and the same would be true in the Sol system. If your faster-than-light (faster-than-Causality) Drive wasn't an instantaneous Jump like above, Causality is still not violated, because you'd still be arriving at NOW + <however long it took> to travel between Sol & Alpha Centauri. Maybe you could only travel at twice the speed of light (twice the speed of Causality), in which case you'd arrive there in NOW + 2.1835 years
- davrosthedalek 6y ago
  The problem with this is that there is now an unaccelerated, moving (with relation to here/Alpha Centauri) system in which you appear in AC before you leave here, i.e. break causality.
  - scarygliders 6y ago
    No, there really isn't, and my post explained precisely why.
  - mrfusion 6y ago
    But that system would see a strange thing but it wouldn’t be sending information backwards because they wouldn’t be able to act on that information on earth or AC. Maybe it’s the same as how I can move a beam of light across the moon faster than light but that’s ok since it can’t send information. Am I misunderstanding it?
- lalaithion 6y ago
  This is not our current understanding of Physics.
  - scarygliders 6y ago
    Please elaborate.
- Dylan16807 6y ago
  That's called having a privileged reference frame, and yes, if your FTL jumps all use the same reference frame then there's no way to violate causality.