what is the present, but a way of describing the moment in time we are in?
And for that matter, the same can be said of the past and future...
In reality, we cannot travel to the future, because wherever and whenever we are, it is "the present"... However, I believe it is possible to travel through time to what I like to call a "relative future".
What I mean by that is, yes, technically, it is the present, but it is further on the time-line than where you left off.
If you believe Hawking's Model of Time, which depicts time as a funnel shape that, when it reaches the bottom, precedes to rise up again, continuing the spiral and repeating over and over again, yet never crossing, you will note that at some instances, time periods are extremely close to each other.
I believe that due to this proximity, latent energy is passed along between time, allowing physical manifestations of past figures (believed to be ghosts) and future figures (believed to be aliens) to interact with present figures (us).
And, if that is true, we can conjecture that, if we find a way to transfer our energy over that link in time, we can, in fact, transfer our own physical beings into another time period.
[my rebuttal, sir!]