This is kind of cool. Theoretical physicists now figure that wormholes, if they exist, would be pretty much useless for space travel...
Traversable Wormholes Useless for Space Travel
Science fiction and space fantasy seldom address the biggest pitfall of traveling through wormholes or diving into black holes... Einstein's "Time-Dilation" effect.
Due to the enormous gravitational forces necessary to bend Space/Time and create a wormhole, you'd probably get sucked right through the thing at near-lightspeed, which sounds pretty fast, right?
It might SEEM like a shortcut to the passengers of a spacecraft going to the other side of the galaxy, but... As it approaches, say, 99.99% the speed of light passing through the wormhole, the spacecraft and its passengers attain infinite mass, and Time SLOWS DOWN for the wormhole-travelers relative to normal Space/Time.
So, BOOP, we just went through a wormhole in what seemed like a few seconds or minutes; but what we may not realize is that the civilization we left behind is now extinct, because perhaps a million years have passed in normal Space/Time. We turn around, go back through the wormhole and, BOOP, now we're TWO million years in the future and there's absolutely nobody there to welcome us home.
So, kind of goes without saying that a trip through a wormhole (if it is ever possible) is going to be a one-way migration into the distant future.
-- Zesko Whirligan