Time travel is almost scientifically proven possible.
But why don't we already have time travelers?
Think of a beam of light. The beam, obviously, moves at the speed of light. When you send it, it arrives microseconds after it was sent.
Imagine we could send a beam from point 1 faster than the speed of light.
We are now discovering this may be possible. The laws of nature and quantum physics say that as long as something is moving at/under the speed of light, all "time frames" will be the same. What happens at each exact second in the universe will coexist and happen at the same rate.
Now, we are realizing that point 1 (moving faster than the speed of light), may actually move so fast, they move at faster rates than the rest of the universe. We may then be able to observe it at point 2 before it was actually sent, because the signal's rate was moving faster than everything else's.
Think of how you see lightning before you hear thunder during a storm. Because light is faster than sound. Now its the other way around, this is faster than light. It happens faster than time (as light) can travel. Happening before it even actually happened.
Next, point 2 sends a signal back even faster. This signal should then arrive at point 1 before the original message was sent.
Know the equation "E = mc^2"? Do you know what it means? Energy = mass * speed of light * speed of light.
sqrt(E/M) = c
The more something weighs, the more energy it takes it get the the speed of light. By this theory, it will take something more and more and more energy to send something even a gram heavier.
So, one could ask... "If time travel is possible, why don't we see any time travelers?". There are now two answers to this question. One is, we can only send a signal (which is actually way more probable than sending anything that has mass. Anything with any sort of detectable mass would take literally infinite energy to accelerate to the speed of light.) so far back. We aren't anywhere near being able to do it, they literally can't reach us yet.
Two, is that there are time travelers. Coming back again to the weight idea, the future can only send things that weight several ounces. Maybe say... a newborn baby? The prodigies of the world may be from the future. That is why they don't fit in. The human race evolves to be more intelligent, and rich people send them back in time to wish them a good life with an undeniable advantage.
Or fuck I don't know, just thinking crazy shit.