https://physics.stackexchange.com/questions/128075/how-would...
Better job, but less accessible: https://physics.stackexchange.com/questions/52249/how-does-f...
The classic version involving FTL ships: http://www.physicsmatt.com/blog/2016/8/25/why-ftl-implies-ti...
A little math, but useful because it applies to the ability to send signals FTL, regardless of means: https://www.quora.com/Why-would-traveling-faster-than-light-...
I like to think of time and space as two different directions you can go i.e. forward/backward (time) or left/right (space). A stationary observer travels only forward, i.e. through time. So they experience lots of time but very little or no space. As you get closer and closer to the speed of light you're moving less in time and more in space. Your vector gets closer and closer to pointing right (using this analogy). An observer traveling at light speed experiences only space, i.e. no time at all.
Then, once you exceed the speed of light your arrow starts pointing a little bit backwards. You're still traveling mostly in space, very little in time but now the time you do travel in is actually negative.
I forget where I read this vector explanation but it's one that makes the concept tractable in my mind :)
Yep. If a photon could talk, it might say "What is this 'time' thing you speak of?"
And since time has no meaning, neither does 'traveling'. A photon is always 'everywhere it's ever been or ever will be' so it might also say "What is this 'space' thing you speak of?"
If you managed to actually achieve the speed of light, the universe would be completely flat. Everything would be contained in a single plane perpendicular to your direction of travel.
So now, what would it mean if you went even faster? The universe would no longer be flat, but would be achieving a negative size. What that really means is not clear to me, but I suppose it's here where the traveling back in time starts to make sense mathematically.
My impression was that the wormhole was used as a "shortcut" between two distant places to avoid having to travel very fast. Imagine a race where everybody else runs the whole course but you take shortcut. You haven't physically travelled fast but your path has been shorter.
I'd guess that Big Banking is blocking the development of this, it'd be a nightmare for inter-galactic ATM machines.
We think of time being this thing that just moves forward around us, and we can't stop it, time just goes.
But in this interpretation, it's us who are falling through time, literally.
I find that fascinating because it changes entirely how I think about the universe. I used to think of the "big bang" as a big explosion of little balls of energy (quarks, electrons, whatever) that eventually coalesced into matter, when enough time had passed and there was enough room for things to cool down. The part that I never understood before this interpretation is how "enough time could pass", when time itself was also supposedly expanding.
But in fact with this interpretation, which I guess is probably more correct (?), space and time simply exploded and began expanding.. which is what we're told but it's hard to picture, exactly. But if you think about energy always moving at the speed of light, and initially all of it flying off in the same direction (time), then matter becomes those particles which were somehow slightly diverted onto the spatial axes -- momentum is conserved, just redirected. And if you think about particles being ripples in fields of non-zero constant energy, an interactions between the fields causing ripples to bump away from each other in non-time directions which we describe as space, this whole relativity thing, and the fact that electric field particles (photons) do not have mass and move at c, starts to make a bit of sense.
It's crazy to think that what we perceive as time passing, the very possibility of things happening, is actually an emergent property of simple geometry and interactions of pure energy.
The way I visualize it is: start two marbles rolling towards each other down an inclined slope. They bump, and bounce off in opposite directions on the X axis. Now imagine there is no table. Would the marbles "feel" anything in the vertical direction? Or would they only feel something in the horizontal direction? Time, for them, emerges from the fact that they can get closer, bump, and move off in the other direction. The other axis, which they are both moving very quickly in, they have entirely in common and they might agree with each other that it is simply a stationary frame which allowed the "bump" to happen. Same for us falling, unrelentingly and unstoppably, through time. (Maybe?)
Gluons are also massless like light, but don't exist on their own. If there's a particle that carries gravity, it would also be massless. You could say light travels at the speed of gravity.
Unfortunately, I am confused about implications of that.
https://www.amazon.co.uk/Why-Does-mc2-Should-Care/dp/0306819...
And it makes it obvious why FTL travel implies time travel
It’s chock-full of a-ha moments and is a pleasure to read
I've heard that many times now, but I'm not sure I fully understand it. So, could someone ELI5 how, given a starship equipped with a warp drive (or in range of a series of cleverly put stable wormholes), how can I give myself winning lottery numbers, and meet my great-great-grandfather?