Long a standard in science fiction, wormholes are used to move the action across immense distances.  Distances that would take several generations to cross at light speed.  Several millennia, actually.  We see them as super-highways across the cosmos.  Want to get to Andromeda?  No problem, just jump into a wormhole and you’ll be there in hours.

Honestly?  That’s pretty close.  A wormhole, basically, is a hypothetical shortcut through spacetime.  If you think of “spacetime” in two dimensions, like a piece of paper, it’s easy to visualize.  Just fold your piece of paper over, and you can see how a wormhole can “bridge” two sections of spacetime to create a shortcut.  Look at this:

Spacetime in 2D - image by en:Benji641 all rights reserved

The 2D image helps you to get a fix on the concept, but it’s really more complex than that.  A wormhole is an unvisualizable structure existing in four or more dimensions.  It’s a tunnel between you and anywhere.  Imagine you want to go to Paris, France, for dinner.  Let’s say you live quite a distance from Paris… like on the other side of the Earth.  You could open a wormhole “bridge” between you and your favorite Paris restaurant and step right over to it.  This image shows that type of bridge between the Physics Building of Tubigen University in Germany and the sand dunes of Boulogne Sur Mer in North of France:

wormhole imagery - Philippe E. Hurbain all rights reserved

That’s fairly easy to imagine, right?  How about a wormhole not between two different locations in the universe, but a wormhole between two different universes?  Imagine two points of gravity (black holes) in two different universes attracting each other.  As they approach, the fabric of spacetime distorts, stretches, and then touches.  The points of contact, two white holes now, meet to form a tunnel.  Look at this:

Merging - image by University of Colorado

That sounds great, doesn’t it?  Well, it does until you get to reading more about it.  For one thing, wormholes are unstable.  Very unstable.  Also, think a moment about those two points of gravity meeting.  You enter at one point, and immediately become stuck in the center.  See, the other point, the “way out”, is drawing matter in towards the center, too.  You can’t turn around and go out the way you came in, because that’s a point of gravity drawing matter in towards the center.  Now you’re stuck in a Schwarzschild Bubble.  You cannot exit either way, because in both ways you’re moving against the force of a black hole.

Okay, how about a wormhole created by a black hole spitting matter out, as in a white hole?  If that possibility exists, you sill have the unpleasant reality of meeting the singularity before your component parts get spat out.  Notice I said “your component parts”, not “you”.  You can forget about “you” at this point.  I guess the labeling of the parts of the wormhole should provide clues to its nature; the mouth, the throat… doesn’t sound promising.

Cover art of "Portal" video game - Valve Corportation, Microsoft Studios - Game uses wormholes to traverse areas of play

Still… if only.  It would be great to pop into a wormhole and exit on the other side of the galaxy. I know there are more types of wormholes than I covered here, and some of them sound promising.  What’s your favorite?  Do you think a human could ever survive a trip down a wormhole?  Could we get back home?