How to spot a Wormhole

Wormholes may be purely theoretical, but that hasn’t stopped researchers from developing a method to locate them.

Wormholes — tunnels in spacetime that allow almost instantaneous passage from one location in the Universe to another — have long been an element of science fiction tales and thus, are a mainstay of pop-culture. But, these passages through spacetime have their origins in the formulation of Einstien’s theory of General Relativity.

More formally known as Einstein-Rosen bridges, wormholes emerge from a particular solution of the Einstein field equations that form the foundations of general relativity.

And though wormholes remain strictly theoretical with no solid evidence of their existence, that hasn’t stopped researchers Dejan Stojkovi, PhD, cosmologist and professor of physics in the University at Buffalo College of Arts and Sciences and De-Chang Dai, PhD, of Yangzhou University in China and Case Western Reserve University from describing a method to spot them. Their findings are published in the journal Physical Review D.

A popular depiction of a wormhole connecting two points in curved spacetime. The light beam travels the spacetime curve the long way around whilst the Einstein-Rosen bridge offers a quick route from one side to the other. (Shuttershock)

The two physicists built the model of detection around the supermassive black hole believed to lurk at the centre of the Milky Way — Sagittarius A*. Of course, there’s no actual evidence no a wormhole exiting by Sagittarius A* — or anywhere else. But, as these spacetime events would require extreme gravitational conditions to exist, looking for them around supermassive black holes is a decent start.

The method the scientists developed suggests that were a wormhole to exist around Sagittarius A* nearby stars should be influenced by the stars at the opposite end of the passage. That means that the presence of a wormhole could be inferred by small deviations in orbits of stars near the Milky Way’s central black hole.

Stojkovic explains: “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.

“So if you map the expected orbit of a star around Sagittarius A*, you should see deviations from that orbit if there is a wormhole there with a star on the other side.”

Unfortunately, if wormholes do exist, Stojkovic notes that a trip through one as seen in science fiction tales may be implausible at best.

“Even if a wormhole is traversable, people and spaceships most likely aren’t going to be passing through,” he 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.”

The pair of scientists suggest that astronomers could search for a wormhole in the vicinity of Sagittarius A* by focusing on the star S2 — which orbits the black hole — and looking for perturbations in its orbit. The catch is that current methods of observing S2 are not sensitive to spot such disturbances to its path around the centre of the Milky Way.

To combat this, Stojkovic says that researchers could collect data on S2 over a longer period of time whilst simultaneously developing methods to track its orbit with greater precision. He adds that these developments may not be so far away, within reach within the next few decades even.

A simulation of the orbit of the star S2 around galactic centre. The technology does not exist yet in order to accurately measure the perturbations in the star’s orbit that could infer the presence of a wormhole. (ESO)

Despite the potential for technology to catch up to this theory in a relatively short period of time, there remains another problem. Simply detecting a perturbance in the orbit of S2 won’t conclusively show it is a result of a wormhole. This is only an inference.

“When we reach the precision needed in our observations, we may be able to say that a wormhole is the most likely explanation if we detect perturbations in the orbit of S2,” Stojkovic says. “But we cannot say that, ‘Yes, this is definitely a wormhole.’ There could be some other explanation, something else on our side perturbing the motion of this star.”

Whether traversable or not, the curvature of spacetime should be observable on both sides of the Einstein-Rosen bridge. This makes wormholes fascinating source of theoretical study and discussion, and as Stojkovic points out “ a legitimate solution to Einstein’s equations."

As such wormholes are much more than just the stuff of sci-fi screen and page — in theory at least.