Wormholes and Space Travel

Space travel through wormholes sounds like quite an interesting idea. Who wouldnt like to have the technology to hop in a ship, find the nearest wormhole and travel to distant places in a short time? It would make space travel so easy!   Of course, the idea pops up in science-fiction movies and books all the time. These tunnels in space-time supposedly allow characters to move through space and time in a heartbeat, and the characters dont have to worry about physics. Are wormholes real?   Or are they only literary devices to keep science-fiction plots moving along. If they do exist, whats the scientific explanation behind them? The answer could be a little of each. However, they are a direct consequence of general relativity, the theory first developed by Albert Einstein early in the 20th century. However, that doesnt necessarily mean that they exist or that people can travel through them in spaceships. To understand why theyre even an idea for space travel, its important to know a little about the science that might explain them. What are Wormholes? A wormhole is supposed to be a way to transit through space-time that connects two distant points in space. Some examples from popular fiction and movies include the movie Interstellar, where the characters used wormholes as portals to distant parts of the galaxy. However, there is no observational evidence that they exist and theres no empirical proof that they arent out there somewhere.   The trick is to find them and then figure out how they work.   One way for a stable wormhole to exist is for it to be created and supported by some kind of exotic material. Easily said, but whats exotic material? What special property does it need to have to make wormholes? Theoretically speaking, such wormhole stuff   has to have negative mass. Thats just what it sounds like: matter that has a negative value, rather than regular matter, which has a positive value. Its also something scientists have never seen. Now, it is possible for wormholes to spontaneously pop into existence using this exotic matter. But, theres another problem. There would be nothing to support them, so they would instantaneously collapse back in on themselves. Not so great for any ship that happens to be passing through at the time.   Black Holes and Wormholes So, if spontaneous wormholes arent workable, is there another way to create them? Theoretically yes, and we have black holes to thank for that. They are involved in a phenomenon known as an Einstein-Rosen bridge. Its essentially a wormhole created due to the immense warping of space-time by the effects of a black hole. Specifically, it has to be a Schwarzschild black hole, one that has a static (unchanging) amount of mass, doesnt rotate, and has no electrical charge. So, how would that work? Essentially as light falls into the black hole, it would pass through a wormhole and escape out the other side, through an object known as a white hole. A white hole is similar to a black hole but instead of sucking material in, it repels material away. Light would be accelerated away from a white holes   exit portal at, well, the  speed of light, making it a bright object, hence the term white hole.   Of course, reality bites here: it would be impractical to even attempt to pass through the wormhole to begin with. Thats because the passage would require falling into a black hole, which is a remarkably lethal experience. Anything passing the event horizon would be stretched and crushed, which includes living beings. To put it simply, there is no way to survive such a trip. The Kerr Singularity and Traversable Wormholes There is yet another situation in which a wormhole might arise, from something called a Kerr black hole. It would look quite different than a normal point singularity that is what astronomers think make up black holes. A Kerr black hole would orient itself in a ring formation, effectively balancing the immense gravitational force with the rotational inertia of the singularity. Since the black hole is empty in the middle it could be possible to pass through that point. The warping of space-time in the middle of the ring could act as a wormhole, allowing travelers to pass through to another point in space. Perhaps on the far side of the universe, or in a different universe all together. Kerr singularities have a distinct advantage over other proposed wormholes as they dont require the existence and use of exotic negative mass in order to keep them stable. However, they havent yet been observed, only theorized.   Could We Someday Use Wormholes? Putting aside the technical aspects of wormhole mechanics, there are also some hard physical truths about these objects. Even if they do exist, it is difficult to say if people could ever learn to manipulate them. Plus, humanity really doesnt even have starships yet, so figuring out ways to use wormholes to travel is really putting the cart before the horse.   There is also the obvious question of safety. At this point,  no one knows exactly what to expect inside a wormhole. Nor do we know exactly WHERE a wormhole could send a ship. It could be in our own galaxy, or perhaps somewhere else in the very distant universe. Also, heres something to chew on.   If a wormhole took a ship from our galaxy to another one billions of light-years away, theres a whole question of time to consider. Does the wormhole transport instantaneously? If so, WHEN do we arrive in the distant shore? Does the trip ignore the expansion of space-time?   So while it may certainly be possible for wormholes to exist and function as portals across the universe, it is considerably less likely that people will ever be able to find a way to use them. The physics just dont work out. Yet.   Edited and updated by Carolyn Collins Petersen