Time travel? Maybe

This all might seem like good news, but the fine print on wormholes is pretty daunting when you get into it. For one thing, we’ve never discovered anything like the exotic matter needed to prop wormholes open, and for another, we’re not sure how we — or even a supercivilization — could punch a hole through the universe to create one in the first place. Furthermore, the idea of time travel is so anathema to many respectable physicists that some, including Stephen Hawking, have proposed a “chronology protection conjecture,” basically insisting that physics must somehow outlaw time machines in order to keep “the universe safe for historians.”

Theoretical physicists have the luxury of being able to invent things that don’t, or perhaps can’t, exist. In the three-quarters of a century since Einstein thought up wormholes, we haven’t come close to observing one, though we’ve gotten some fantastic science fiction in the bargain. It may be that in science fact, if we want to explore the galaxy, it would be much easier to do so without trying to rip up the fabric of space-time in the process.