This world - this Universe - is a very strange place made even stranger by the verifiable theories of Quantum Mechanics and other things that deal with the very small. Especially when one considers that same Universe in light of the three dimensional world in which we live. Well, four dimensional if you add Time. But strange, nonetheless.
One of those strange things?
There are many physicists who subscribe to the principle that there are as many as eleven actual dimensions to our Universe - and some of these extra dimensions are curled up into things called "Strings" - as in "String Theory". Part of the supporting argument for multiple dimensions is that Gravity, which is inexplicably weak in our three dimensional Universe, has to spread itself into all the other dimensions - thereby weakening it in any one dimension.
But what if there was a dimension that wasn't all wrapped up in strings, but was unimaginably large? What if there were to be another physical dimension to our Universe, a fourth physical dimension, one so large we cannot perceive it, just as the beings of Flatland (It's a book about life in a 2 dimensional universe) had no concept of or ability to see our three dimensions. And what if there was matter that existed in that fourth dimension - matter whose only effect on OUR three dimensions would be the gravitational effect of that fourth dimensional matter.
What if we could find a way to traverse that fourth dimension in order to move from one place to another in our three dimensions? Would we be out of the flow of time in our three dimensions? Would this be how we populate the Galaxy? Multiple Galaxies?
If we, our species, don't find a way to disperse ourselves beyond this world, out into the Galaxy, we who are the Universe come to know and admire itself will not survive. We live on a time bomb - a cosmological target - and someday there will be an extinction event. An asteroid or comet of size, that we cannot deflect or avoid, will strike the Earth and Mankind will be gone.
Fourth Dimensional travel could be the answer.
Provided, of course, the Fourth Physical Dimension exists.