Time travel could be achieved if a wormhole was found. First off, you can think of space and time as "fabric" (the fabric of space and time). As you probably know, fabric can be wrapped around and twisted in different shapes. Well, the larger this fabric is and the more it twists and turns, the more likely different parts of it are to touch. When two parts touch, this is a wormhole. Wormholes do in fact exist, and aren't a complete work of science fiction. The only reason we don't see wormholes, or travel through them is because it requires a massive amount of energy. In fact it would take the energy of a supernova to travel through one. Wormholes are actually all around us, and I'm sure if it was possible to harness that kind of energy we could find a way to manipulate this "wormhole technology" we could travel through space and time. Hope that helped.
Time travel to the future is arguably possible due to the phenomenon of time dilation. The possibility of backwards time travel is currently unknown, though it could occur by travelling faster than light or using black holes or wormholes.
Scientifically, I believe most anything can be possible. I highly doubt time traveling into the past is possible, otherwise we most likely would have heard about it by now. When going into space, you become very slightly younger then you would be if you stayed on earth. I forget why, and I forget where I read this. Sorry.
I theorize that the Bermuda triangle made the lost flight squadron travel backward in time since they originated from area 51. I believe that's why area 51 originally shut their gates to the outside populace without giving a reason: they uncovered the old flight crew. That and they need a place to store alien technology they discovered. I know for a fact they have sheets of metal they can't recreate that disperses heat instantaneously.