The physical possibility of time traveL is something of a catch-22. Any object that’s surrounded by the twisted space-time that time travel requires must by its very nature be fantastically perilous, a maelstrom that would inevitably tear apart the foolhardy traveler. So physicists have labored to create a theoretically acceptable time machine that’s free from nasty side effects like certain death. Their starting point: black holes.

Black holes are famous for sucking in everything around them—including light—and never letting go. But black holes have other characteristics, namely the way they bend nearby space-time. A black hole is infinitely dense, which means that it pulls the fabric of space-time to the breaking point—creating a deep pockmark, complete with a tiny rip at the bottom. More here.