Maybe this is how we can travel to other galaxies in our lifetime?
Madhavi Gavini posed this great question here: What is the probability of man exploring other galaxies in our lifetime? (http://www.ted.com/conversations/14450/what_is_the_probability_of_man.html?c=552358). I responded with a discussion of how much energy it would take us to travel there and that therefor this would be impossible for quite some time. Then I read a blog posting about why haven't we seen aliens yet? And I started thinking...
The problem is that it takes too much energy to accelerate our massive human bodies to near light speed, where we could take advantage of time dilation effects to travel many light years within the life time of a person on such a trip. So what if...
What if alien civilizations, millions of years more advanced than us, have folded the space time continuum in such a way as to create hills that are always running downhill or uphill, fed by gravity. One side or the other would always be running "up hill" or "down hill" which would send you one way or the other in the universe, and the two sides would perfectly balance each other out. A bit like one of Escher's infinite staircases.
Such superhighways could be shielded with gravitational lensing so as to be undetectable to us here on earth, and there would be on-ramps to allow you to control your own acceleration. Not knowing where one is located, the odds of us finding one by chance would be pretty much impossible.
But if someone shows us where it's located, or sends out a beacon - then we could use normal rocket power to maneuver close to one of these gravity superhighways, jump on the downhill side and just "coast downhill" up to just under the speed of light, reach the halfway point of your trip, and flip around to the other side of the highway to slow down (going uphill effectively).
So this is a shout out to any aliens listening out there, to please show us where you've folded space time so we can explore the universe too.
Does this idea have any merit?