Like wars erupting over FTL rather than sharing it, because the country or a corporation who would be the first to have such technology stands to have the potential to colonize distant planets.
Like wars erupting over FTL rather than sharing it, because the country or a corporation who would be the first to have such technology stands to have the potential to colonize distant planets.
If FTL was ever invented, we’d have paradoxes where effects happen before their cause, so literally anything is possible.
You could jump forward and observe yourself, but you’re not actually there anymore. It’s kind of like shouting in to a long tube.
What kind of paradox would you see happening? (pun intended)
https://en.wikipedia.org/wiki/Tachyonic_antitelephone
Basically, an “instant” communication device can create paradoxes.
E.g.
Earth sends mars a instant message. Mars the relay’s it via normal radio to a passing ship/probe moving at 0.99C. That probe then sends an “Instant” message to Earth.
The final message will (depending on alignments etc) arrive before the original was sent. If the message the voids the reason for the original message to be sent then a paradox happens.
You can make similar things happen with any form of FTL communication. C isn’t technically the speed of light, it is the speed of information. It just happens that light has no other speed limiting, and so moves at maximum speed.
The reason why there will be paradoxes (where an observer can see a message and send a reply that arrives back to the sender before they sent the message) is explained basically everywhere FTL is discussed.
The explanation isn’t trivial enough for a comment field, so have a link:
https://www.youtube.com/watch?v=an0M-wcHw5A
Anytime you move at a different speed, the definition of what time matches your current time shifts throughout the universe by an interval proportional to the distance—even if you’re just driving down the street, the time that matches “now” in your reference frame in a distant galaxy could change by years relative to what it was when you were stationary. Of course, you can’t actually see that happening, so the difference is just theoretical… as long as you can’t teleport to that galaxy faster than light.
But as soon as you have any kind of FTL travel, it’s trivially easy to go back in time by warping back and forth between two moving endpoints.
That is not how speed works in relativity. Even moving with 10 times the speed of light, you still take “forward time” to move to your end point.
What will be happening though is that your point of reference will seem to travel backwards related to your starting point IF you travel away from your starting point.
So you move with FTL from A to B, then you will see A’s past light, which you overtook while traveling to B, arriving at B, thereby seeing your past “as happening now”, but only at point B. But the time will still be ticking forward. And while you travelled to B, you raced against the light coming from B, meaning you travelled faster into the future of B.
If you then travel back with same speed from B to A, you will still be in the future from when you started in the first place. But you will see yourself standing at B. And again, while travelling from B to A, you raced against the light coming from A, meaning you saw that future happening at FTL speed.
There’s no such thing as speeds faster than light—the worldlines of objects with such trajectories are called “spacelike” instead of “timelike” for a reason. “Forward” and “backward” time is only defined for events within your light-cone, and trajectories “faster than light” are outside it. Whether events outside your light-cone are in your future or your past are dependent on your current reference frame, which you can change at will by accelerating—so spacelike trajectories have no intrinsic direction with respect to time.
The thing about “moving with FTL from A to B” is that if B is far away, the event at B simultaneous with your departure from A will be highly dependent on A’s reference frame—a shift in A’s velocity will correspond to a shift in B’s timeline equal to (vx/c2)/√(1-v2/c2) (where v is the change in A’s velocity and x is the distance to B). And things are changing velocities with respect to each other all the time (e.g., for objects on earth due to the planet’s revolution and rotation around the sun), so the point in B’s timeline at which you’d arrive would be constantly swinging backward and forward in time.
And the same is true for the return trip: a minor change in B’s reference frame can put your arrival back in A’s timeline at a point before your original departure.