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Well, I'm going to give the party-pooper response, even though science fiction and pop-science love to fantasize differently:
The past and the future are theoretical concepts. They don't actually exist in the sense that you can 'send' something to them.
Obviously, you can write data to a hard drive and then read it out after a week has passed, but presumably that is not what you had in mind.
But that's also the essence of the time travel that the theory of general relativity allows. You can travel forwards more slowly along the time axis by travelling more quickly on the space axis (close to the speed of light), which means you might just need to spend 5 perceived years to end up in the year 2200.
Similarly, you could take a hard drive onto this journey and it wouldn't have fallen apart in that time.
Travelling back in time makes no sense in general relativity. You would need to reverse causality for that, which is on an entirely different level from merely slowing causality down.
General relativity would mathematically allow for the existence of wormholes, but that's pushing the theory to extremes where it might simply not be applicable to reality anymore. We certainly have no actual evidence for wormholes.
Even wormholes break causality. Doesn't matter the method, folding space, black holes, if you can arrive at a destination faster that light thru normal space can get there, you can know of things before they occurred.
Hmm, but why do you think these things haven't occurred yet?
As far as I can tell, the speed of causality means things can have occurred in a certain location in the universe, but it takes time until the effects have permeated into the rest of the universe.
So, it's like a shockwave from an explosion. The explosion happens, but it takes a few seconds until you feel the shockwave.
Well, with the difference that you can see an explosion before the shockwave. When we're at the speed of causality, literally no evidence will have arrived in your position until it does.
So, one could go meta-philosophical with basically "If a tree falls in a forest and no one has heard it yet, did it actually already happen?", but yeah, I don't think that's terribly useful here.
And well, if we treat it like a shockwave, let's say you detonate some TNT and step through a wormhole to somewhere 20 km away. You would know that the shockwave will arrive soon, but does that matter? The shockwave will still just continue pushing on.
And I guess, crucially, it did already happen, so you can't do the usual time travel paradox of preventing that it would happen.
If I understand you correct, it is not important that you know if it before it happened, because literally no evidence will have arrived until it does. Except that is not correct. Your knowledge is literally and entirely evidence so something did arrive. Effectively you are in a timeline that is behind the event's timeline.
But more to the point, you could take this knowledge, fold the universe again, and being that you are in a timeline prior to the event, you could arrive at the source event before it happened. And stop it. The paradox then. How did you know to do something that never happened?
And you wouldn't have to reverse causality to travel backwards in time. You would just have to travel faster than the speed of light.
If you can travel faster than the speed of light then you can arrive at a destination before you left.
Alternatively, you would need to generate some sort of negative energy and then enter into a wormhole with the negative energy. As you cross the perihelion of the wormhole there is a possibility that rather than being crushed and destroyed and by the unimaginable cosmic forces you are experiencing that the negative energy would cancel it out and you would be able to travel through the wormhole to any point between the moment that you entered it and the moment that it was created.
Both of these statements come with the caveat that these are based on theories and so my ability to explain them is limited not only by my understanding of the theory but also my ability to explain the information that I have, and there is the possibility that even though these are somewhat plausible scenarios once you overcome the massive gap between where we are and where we would have to be to implement them, there is a chance that a new better mathematical theory will replace this information and prove it to be completely and totally false.
Another term for the speed of light is the speed of causality as it is the rate with which causality propagates through the universe.
Traveling faster than the speed of light is, by definition, reversing causality.
I think you're looking at it from the wrong frame of reference.
Technically, time is still moving forward. Time has not moved backwards on a universal scale, you have just traveled in such a way that you arrived at a point in time where your temporal reference frame is different than the rest of the time you are currently occupying.
Your causality has remained uninterrupted by traveling faster than the speed of light.
Traveling faster than the speed of light means that you have exited the universe and re-entered it at a different point.
At the point that your causality reintegrates with the current temporal causality that you find yourself in then a new causality is created.
Once again, this does not alter causality.
You've just put a stitch in time.
I know practically nothing about all the wormhole theories, because I just don't consider them relevant, but from a logical standpoint, the above does not feel correct to me.
The thing is, you would arrive at your destination before the light would arrive there from where you started. So, you could take out your telescope and potentially watch your own launch.
But that doesn't actually put you into the past. It just looks like it when looking into the direction you came from. Light from the other direction will look like you've fast-forwarded through time, because you now get more recent imagery.
I don't have another explanation why someone might think, this might put you into the past...