Reverse Time Dilation for interstellar travel

[Solarspaceprobe]

Hey, in January I was writing for a project, when I realized all futuristic spaceships go long distances almost always the same way. They either warp the fabric of the universe, speed up a ton(in the looser sci-fi like Star Wars), or go through a wormhole of some sort. I wanted to be original. Well, I realized I remembered seeing something about a relationship between time and speed, like when you go close to light speed you appear to be moving "slow" to everyone else. I looked around for a while and found that both gravity and velocity strengthen the time dilation effects. And then it hit me! Why not use anti-gravity(assuming you DO have it, in sci-fi you normally do) and make time dilation reverse, shooting your spaceship through time? You'd have to freeze the crew members or something, as the trip would likely be LONGER for them, but Earth wouldn't have to wait a hundred thousand years for it's starships to send the "we made it and we're okay" message to prove it was worth it. Would it work?

[Z-Man]

It's your SciFi universe, so if you think it is cool, then yes, it can work.

In this universe, it's pretty much on the same reality level as the Warp Drive; you're doing pretty much the same thing with a slightly different result. For your antigravity, you need some kind of exotic matter we don't have yet in sufficient quantities. For the ship to move at apparent FTL from the point of view of outside observers, you need to be able to manipulate spacetime in front of the ship quickly enough. Those are the exact same unsolved problems the Alcubierre drive has.

[sojourner]

You might want to do some more background research into the subject in general. A good resource page for writers is Atomic Rocket.

[WestAir]

I have heard that gravitationally induced time dilation causes the person closer to the larger gravity well to see time slower, and unlike velocity induced time dilation, all observers agree that time is going slower for those closer to the center of gravity.

I imagine with exotic matter that creates negative gravity, the effect could go in reverse (all observers see the person near the exotic mass as having faster time) - but it's also possible that there is a hard limit. (I.E, you can't make time go faster than the natural global dilation of the cosmic microwave background observer, only slower). But I'm just guessing here.

[YNM]

I'd imagine it to be a sort of alcubierre drive in the end. Haven't read (or thought) well about gravitational time dilation but I think now that it's due to the curvature of spacetime, changing the distance a light pulse must travel.

[Technical Ben]

So if we add to what WestAir said, your drive would seem to accelerate the "time" within the bubble (or ship) and all would agree it's travelling FTL (still impossible, but handwavey/sci-fi enough for a plot). As you said, the crew would need to be frozen though, as awakening during transit would mean you live out decades or even more during transit, while on the outside it looked like a few hours/days to travel to your destination.

Though, you could theoretically have a bubble inside a bubble. If you can create a "faster time" bubble, why not a "slower time" one to? So if the ship is going really fast, the crew inside could be in a "safe" area in the bubble. It could also be used for shielding, slowing down incoming projectiles. It would also mean little to no communication while in flight (possible but hard) and dangerous transit if someone launched an escape pod during flight. Perhaps the escape pod only crosses the border of the bubble for a few seconds, but inside the pod days go by...

[Brethern]

The aliens franchise's FTL actually does this, time speeds up for everyone on the ship hence the reason why they need cryo.

[Bill Phil]

But why? Time dilation doesn't effect velocity externally, just the perception of time internally. So really you wouldn't want to at all counter act the relativistic effects, it's stasis that comes with speed.

Btw, a good time dilation balance to speed and normal time is .5c. The time dilation effect isn't huge, and you do get around quick. But for far distances you would want hibernation. Heck, just always use it. It'll take a decade nearly to get to the nearest star system, so it would be a good idea. Plus it takes a lot less energy to get to half light speed than 70%.

[LaytheAerospace]

Before you make up your mind, I suggest you read The Forever War. It's the best depiction of space travel I've ever seen in fiction. That's not to say it's a slave to real physics, there's a concept of a "collapsar jump" that allows traveling between black holes with nearly zero passage of time, but this doesn't help you actually get to the black hole to begin with, or slow you down on the other side when you pop out moving at .999c. That all involves traditional acceleration, and the time dilation that goes with it.

The results are...messy. As they should be.

[WestAir]

... Earth wouldn't have to wait a hundred thousand years for it's starships to send the "we made it and we're okay" message to prove it was worth it. Would it work?

Going back to this thread, I have to ask what you meant by this phrase.

Either we're using a warp drive and both the traveler and the people back home aren't under the influence of near-C time dilation, or, we're flying at 0.9999c and the crews time is slowed. Speeding or slowing their time does nothing for those on Earth: The trip will always take ~1 lightyear to go 1 lightyear. Unless you slow down the passage of time on Earth to match the velocity time dilation on the ship - which would be pretty epic.

[Rakaydos]

The aliens franchise's FTL actually does this, time speeds up for everyone on the ship hence the reason why they need cryo.

Is this ever actually said? I was under the impression that is was simply a matter of a sub-kilolight FTL drive (less than a thousand times the speed of light) still taking days or weeks per lightyear.

The 10c warp drive being theorized would take over a month per lightyear, or almost half a year to get to our nearest star. If the jumps in Aliens are in the 10-20 lightyear range, cryo might still be nessisary.