But their precise shape has been unknown.
Now, however, a physicist in Russia has devised a method to measure the shape of symmetric wormholes — even though they have not been proven to exist — based on the way the objects may affect light and gravity. [8 Ways You Can See Einstein's Theory of Relativity in Real Life]
In theory, traversable wormholes, or four-dimensional portals through space-time, might work something like this: At one end, the irresistible pull of a black hole would suck matter into a tunnel connected at the other end to a "white hole," which would spit matter out at a location far away from the material's point of origin in space and time, according to Live Science's sister site, Space.com. Though scientists have observed evidence of black holes in the universe, white holes have never been found.
However, even though wormholes may or may not exist, scientists do know a lot about the behavior of light and gravitational waves. The latter are the ripples in space-time that swirl around massive objects such as black holes.
One wormhole property that could be observed, albeit indirectly, is a redshift in the light near the object, the new study said. (Redshifting is a decrease in the frequency of light wavelengths as they travel away from an object, resulting in a shift to the red part of the spectrum.)
If you know how light around a potential wormhole is redshifted, you can then use the frequencies of gravitational waves, or how often they oscillate, to predict the symmetrical wormhole's shape, said study author Roman Konoplya. He is an associate professor with the Institute of Gravitation and Cosmology at the Peoples' Friendship University of Russia (RUDN).
Typically, researchers work the other way around, looking at the geometry of known shapes to calculate how light and gravity behave, Konoplya told Live Science in an email.
There would be a couple of methods for checking the redshift near a potential wormhole, Konoplya said. One would use gravitational lensing, or the bending of light rays as they pass by massive objects — like, possibly, wormholes. This lensing would be measured in its effects on faint light coming from distant stars (or on brighter light from a nearby star "if we are very, very lucky," Konoplya said). Another method would measure the electromagnetic radiation near the wormhole as it attracts more matter, he explained.
Think of the equation this way: If you strike a drum, the behavior of sound waves produced by the vibration of the taut skin can reveal the drum's shape, Jolyon Bloomfield, a lecturer in the physics department at the Massachusetts Institute of Technology, told Live Science.
"All the different frequencies — that tells you the different vibrational modes of that taut skin," Bloomfield said. Meanwhile, the peaks and valleys of those vibrations gradually decay in time, which shows how the modes are "damped." Those two pieces of information together can help you define the shape of the drum, Bloomfield said.
"What this paper is doing is kind of the same thing for a wormhole. If we are actually able to 'listen' to decaying frequencies of oscillation of a wormhole with enough precision, we can infer the shape of the wormhole by the spectrum of the frequencies and how fast they decay," he explained.
In his equation, Konoplya took a wormhole's redshift values and then incorporated quantum mechanics, or the physics of tiny subatomic particles, to estimate how gravitational ripples in space-time would affect the wormhole's electromagnetic waves. From there, he constructed an equation to calculate a wormhole's geometric shape and mass, he reported in the study.
The technology for measuring gravitational waves has been around only since 2015, with the introduction of the Laser Interferometer Gravitational-Wave Observatory (LIGO). Now, researchers seek to fine-tune LIGO measurements, as better data could help scientists finally determine if there is exotic matter in the universe — matter made of building blocks unlike normal atomic particles. That material could support objects like wormholes, Bloomfield told Live Science.
For now, at least, wormholes are only theoretical, so Konoplya's equation doesn't represent any actual real-world measurements, he wrote in the email. And detectors like LIGOmeasure only one frequency of gravitational waves, while you would need several frequencies to predict a wormhole's shape, Konoplya said.
"From such poor data, it is impossible to extract enough information for such a complex thing as a geometry of a compact object," Konoplya wrote in the email.
Future studies could provide an even more detailed view of a wormhole's shape and properties, Konoplya said.
"Our results may be applied to rotating wormholes as well, provided they are symmetrical enough," he added.
The findings were published online Sept. 10 in the journal Physics Letters B.
Originally published on Live Science.