Can Black Holes Be Used as Cosmic Gateways?

So far, stellar and galactic black holes have been considered in light of how their major properties extreme gravity, accretion disks, quasars, and so forth affect matter, space, and time in the universe surrounding them. Very little has been said about what happens inside a black hole other than that matter is either crushed or falls down the hole’s gravity well forever. This is partly because the inner workings of these cosmic oddities remain largely mysterious. Obviously, there is no known way to see into or directly measure the inside of a black hole.

But that has certainly not stopped people from trying to visualize what lies beyond the enigmatic event horizon. Ever since serious consideration of black holes began in the 1960s, various theories and mathematical equations have predicted that certain things are likely to exist or occur inside black holes. And when the theories have seemed inadequate, investigators have freely used their imaginations. They have wondered, for example, whether bodies outside the hole would be visible from the inside since they know that matter inside a black hole is not visible from the outside. Also, matter that enters a black hole disappears from the regular universe. Does this matter cease to exist, or does it somehow survive and reemerge somewhere else, either in this universe or another one? Moreover, if the matter can survive intact, might it be possible for people, too, to survive a trip into a black hole?

Not surprisingly, science fiction writers have frequently and colorfully exploited these and other bizarre possible qualities of the inner environments of black holes. Most often, they portray these superdense objects disturbing the fabric of space and finally tearing it, thereby creating a small opening. Such an opening and the invisible spatial tunnel it leads to are together commonly referred to as a wormhole. As of yet, wormholes are technically theoretical, although physicists believe they are likely to exist.

Science fiction stories and films usually describe piloted spacecraft traveling through wormholes and emerging either in distant regions of the galaxy or in the past or future. In the popular television series Babylon 5, for example, an interstellar space station floats near wormholes leading to various distant star systems. And in the final episode of the television series Star Trek: Voyager, Captain Janeway uses a wormhole to travel through both space and time in an effort to alter the past. Incredibly, in recent years physicists have shown that these kinds of journeys, though certainly not feasible using existing human technology, are theoretically possible.

Wormholes as Time Machines

Some of the mathematical formulas associated with the theory of wormholes suggest that if one end of a hole is fixed and the other end is moving, each will end in a different time frame. In this excerpt from The Physics of Star Trek, physicist Lawrence M. Krauss tells how writers for Star Trek: Voyager correctly depicted this phenomenon.

Wormholes, as glorious as they would be for tunneling through vast distances in space, have an even more remarkable potential, glimpsed most recently in the Voyager episode “Eye of the Needle.” In this episode, the Voyager crew discovered a small wormhole leading back to their own “alpha quadrant” of the galaxy. After communicating through it, they found to their horror that it led not to the alpha quadrant they knew and loved but to the alpha quadrant of a generation earlier. The two ends of the wormhole connected space at two different times! Well, this is another one of those instances in which the Voyager writers got it right. If wormholes exist, they can well be time machines! This startling realization has grown over the last decade, as various theorists . . . began to investigate the physics of wormholes a little more seriously.