Okay, different topic. I was having lunch with a girl I knew from school. (Cute, but she's married now.) Anyway, she's a scientific journalist, and is working on a story about the latest developments in theoretical cosmology. I always thought, as did almost everyone else, that Einstein had proven that time travel into the future may be possible due to the relativity of time at high speeds. According to him, if you spent a couple of days zipping around the nearest stars at the speed of light, when you returned home, everyone would be old and gray. You would have effectively traveled into the future.
Well the latest research is turning that on its head. It turns out that you can't jump to a future time because it hasn't been defined yet. It's only a probability. But travel into the past, despite all the fretting about paradoxes, may be possible. Look at it this way. 10 million years ago the Earth and the whole solar system was in a different spatial location. Not only is the Earth moving around the sun, but the solar system is drifting in the local star cluster, and the local group is drifting around the Milky Way spiral, etc.
Also, when we look out at the stars in the sky, we are not seeing them as they exist today, but as they were in the distant past. (due to the speed of light across vast distances.) Theoretically, there is a path through space where we could look to see our own planet in the distant past. This would of course require a good enough telescope, accurate calculations, and perfect knowledge of gravitational lensing and refraction; but it would be possible. We could actually look out and see our own world as it existed in the distant past. If the telescope were strong enough, we could look out into space and watch the dinosaurs grazing.
Okay so we can see the past, but that's not the same as traveling there. But... (there's always a but) if we could open a wormhole along that same line of sight, we could step across instantly into that past time frame. A wormhole is an instantaneous gateway through space-time.
The only thing in theory that would preclude this jump into the past is the nature of wormholes. Stepping through a wormhole would annihilate every particle of your body.