By Irina Slav
Wormholes: the modern-day equivalent of the Philosopher’s stone, a concept that has captured the imagination of millions of sci-fi fans and has appeared in multiple films and novels. Alas, all of them are fictional. Yet, wormholes remain theoretically possible, and if they exist, we now have a way of locating them. Sort of.
Last month, a researcher from the University at Buffalo made headlines with a paper that detailed a way of detecting a wormhole in our very own Milky Way galaxy. In it, physics professor Dejan Stojkovic explains that since a wormhole is essentially a tunnel between two points in space-time, and there are presumably stars in proximity to these two points, the gravitational pull of the stars at one end of a wormhole will affect the orbits of nearby stars on the other end.
Here’s how professor Stojkovic explains it: “If you have two stars, one on each side of the wormhole, the star on our side should feel the gravitational influence of the star that’s on the other side. The gravitational flux will go through the wormhole.” It will then affect the orbit of the nearest star on the other end of the wormhole.
But how do you even begin looking for a wormhole to test the hypothesis? It’s not like wormholes are an everyday occurrence – scientists have yet to find proof they even exist, let alone start searching for them.
The one big reason for this is that these theoretical space-time tunnels, which by the way have a more official name, which you likely have heard if you’ve watched Thor. It is called an Einstein-Rosen bridge, and they are incredibly unstable. So unstable that, astrophysicist Paul M. Sutter wrote in a recent article for Forbes, “If you were to find a wormhole and send a single bit of light – a single photon – down the tunnel, the reaction of that photon’s energy to the space-time around it would be enough to completely destroy the wormhole faster than the speed of light.”
One inference a layperson can make from this information is that even if they exist, wormholes would be extremely tough to find because of this tendency to collapse into non-existence as soon as they open. That’s unless they can be stabilized – a task that would necessitate adding something with a negative mass, which is one of the things that we have yet to find in the universe. Until we do, it is as non-existent as (probably) wormholes.
The “probably” part comes from the domain of quantum physics. While classical physics does not allow for the existence of Einstein-Rosen bridges, they are theoretically possible, and quantum physics has space for them, in string theory, in case you still have space for quirky scientific ideas.
String theory replaces the dot-like elementary particles of particle physics with, well, strings: tiny, one-dimensional strings that are the minimum constituent parts of all matter and, notably, all forces, including gravity. These strings vibrate at different frequencies and depending on the frequency, they can gain properties of other particles – photons, quarks, etc. Remember the gravity part.
According to one researcher from the University of California, string theory can explain wormholes in a way that increases the chances of their existence, kind of.
Diandian Wang, a graduate student at the UC at Santa Barbara, says wormholes can form when a string breaks: “It contains energy, and when it breaks, that energy becomes two black holes at each end of the string.”
Wang and his colleagues have also found a way around the instability of wormholes. As Chelsea White writes for New Scientist, the researchers calculated that the curvature of space-time in the wormhole could counteract the mutual push between the two black holes at the ends of the tunnel that would otherwise eventually snap the tunnel shut. Once stabilized, a wormhole could stay open forever, Wang argues.
Back to Professor Stojkovic and wormhole detection. If there is a wormhole in our galaxy and it is essentially a tunnel between two black holes, where is it most likely to be? According to Stojkovic, that would be Sagittarius A* – an object that scientists believe could be a supermassive black hole smack in the middle of the Milky Way.
Supermassive black holes have an extreme gravitational pull, and this makes them the best location for a wormhole: opening up a hole in space-time also needs an extreme gravitational pull.
Problem solved, then?
Not everyone agrees. One physicist, from Russia’s Central Astronomical Observatory, for instance, commented that any alternation in a star’s orbit resulting from the gravitational influence of another star across a wormhole is “unobservable”, Live Science reports. The reason: the only acceleration of a star around its orbit that science can measure is the absolute one. There is no way to distinguish between the “normal” acceleration and the additional one caused by the gravity of a star at the other end of a wormhole.\
Stojkovic has an answer to that. “What we calculate in our paper are variations in acceleration due to the elliptic orbit of a star,” he told Live Science. A star’s acceleration around a black hole tends to be constant, so any variation in it would indicate “there is an additional source of gravitational force.” Presumably, this additional source can only come from a star at the other end of a wormhole.
So, we have the where and the how of wormhole spotting. We might even have a way of making one from scratch (just snap a string, that’s all). It might come as a crushing disappointment, then, that even if they turn out to exist, wormholes will be very different from the ones we see in movies and read about in books.
“Even if a wormhole is traversable, people and spaceships most likely aren’t going to be passing through,” Stojkovic says. “Realistically, you would need a source of negative energy to keep the wormhole open, and we don’t know how to do that. To create a huge wormhole that’s stable, you need some magic.”
We’d certainly need magic because wormholes, as Sutter says, violate several laws of physics. And this is just as well because: “I can’t tell you what would happen if you were to try to travel down a wormhole. My best guess is that parts of you would end up distributed throughout the known universe, which means you technically achieved interstellar travel, but probably not in the way that you had hoped.”