8 ms·
We aren't talking about time travel. So many people confuse the idea of FTL with time travel. General Relativity talks about frames of reference. Suppose you h
by geuis 14y ago
We aren't talking about time travel. So many people confuse the idea of FTL with time travel. General Relativity talks about frames of reference.
Suppose you had a base on Mars and sent a radio signal to it from Earth. It would take between 4.3 to 21 minutes to reach Mars, depending on its distance from Earth at the time.
If you simultaneously jumped in your 10x warp drive and set out, you would arrive at Mars in 25.8 seconds to 1min 26 seconds, again depending on distance.
In this scenario, there has been no violation of causality. You aren't arriving before you sent your radio signal. All that is happening is that you're arriving before your radio signal does. From the perspective of a telescope or radio antenna at the Mars base, you would view Earth in its state 4.3 to 21 minutes before, because it simply takes that long for the electromagnetic waves to get to you.
So yes, you can travel faster than the speed of light without violating causality. If you travel in a relativistic way, i.e. speed all the way up to 99.99999% of light speed, you will most certainly run into time slowing down in your local frame, while it continues at a normal frame back at your departure point.
But with a warp drive that works as described in the article, there is no changing of reference frames. Since you're warping space itself, the spacecraft isn't actually undergoing acceleration in the relativistic way of a rocket. For passengers on board, the clocks are going to run at the same rates as back home.
- politician 14y agoA pair of FTL communication devices (jargon: ansible) can be arranged in a configuration which would allow the future to speak to the past, violating causality.
- nessus42 14y agoYou are not correct. If anything with information travels faster than the speed of light, then there are frames of reference in which that information arrived at the destination before it left the origin. Furthermore, unless your FTL drive is limited in ways that would make it utterly useless, any FTL drive can be used to make "closed time-like loops", which would allow travelers to meet up with their own past selves.
- enraged_camel 14y ago>>You are not correct. If anything with information travels faster than the speed of light, then there are frames of reference in which that information arrived at the destination before it left the origin. No. If you send a radio signal to Mars, and then warp to Mars to find yourself there 0.1 seconds later, you are still 0.1 seconds after the moment on which you sent the signal from the point of origin. You are traveling faster than light, in the sense that you are traveling at [Earth-Mars Distance]/[0.1 sec] speed, but you are not actually traveling backwards in time to a point where you have not sent the signal yet.
- nessus42 14y agoNothing you just said contradicts my statement, which was, "there are frames of reference in which that information arrived at the destination before it left the origin." I suspect that you don't know anything at all about Special Relativity, in which case, there's not much more I can tell you except to go educate yourself.
- teamonkey 14y agoSpecial Relativity only applies to cases where there is uniform relative movement in two or more inertial frames of reference. That is not the case with this theory - the relative movement is clearly not uniform and although I've not read the paper I'm certain that the time warp provides a non-inertial frame. TL;DR - ignore Special Relativity completely, General Relativity is the only thing that applies here.
- nessus42 14y agoSpecial Relativity applies ANY TIME that you transmit information from one point A in an inertial frame to another point B in an inertial frame. If you can use your warp drive to transmit information from A to B, then Special Relativity applies. If you cannot use your warp drive to transmit information from A to B (e.g., from Earth to Mars), then what good is it? (I've mentioned several times in this thread that you might be able to come up with some sort of FTL drive that doesn't violate causality if you put enough constraints on it to make it useless.)