4 ms·
I've never managed to see how causality is a problem for FTL travel If we perceived the world through sonar then causality would be violated by anything supers
by circlefavshape 5y ago
I've never managed to see how causality is a problem for FTL travel
If we perceived the world through sonar then causality would be violated by anything supersonic. If you were shot then you'd feel the bullet first and then "see" it moving back into the gun.
AFAICS if information can travel at >c, then physical objects traveling at >c doesn't violate causality
- harpersealtako 5y agoHere's a good explanation of why FTL causes causality issues. http://www.physicsmatt.com/blog/2016/8/25/why-ftl-implies-time-travel http://www.physicsmatt.com/blog/2016/8/25/why-ftl-implies-ti... The sonar example works only if everything is traveling in roughly the same frame of reference. You're not accounting for relativity and its effects on space and time in your analogy.
- circlefavshape 5y agoI still don't get it. That analogy assumes that light is the only way causality information can be transferred - i.e. if I see the phone call being placed before its sent then it seems like causality is violated. But it I look at what's happening via the FTL phone then I can see that it's not
- sxp 5y agoComparing to sonar isn't valid since objects at subsonic and supersonic speeds still obey the rule that 1 + 1 = 2. For high velocities, this rule is no longer true and you need to resort to using a spacetime diagram to compute velocities. If you draw a tachyon on a spacetime diagram going faster than the speed of light, you can create situations where the tachyon travels back in time for certain observers. > AFAICS if information can travel at >c, then physical objects traveling at >c doesn't violate causality If information can travel faster than c, then you can create situations where it's also violating causality.