– What if our Universe is just one of many universes co-existing next to each other? The “multiverse” theory has been treated by physicists as intriguing, but so far it has remained in the realm of theory without any experimental tests that could support it.
Finding evidence of parallel universes is very challenging. Scientists have hoped that the Large Hadron Collider (LHC) might reveal evidence of their existence, but so far definitive proof has not been discovered with the LHC.
Physicists have studied gravitational waves, ripples in space-time caused by the motion of massive objects and now they suggest these waves might allow for a single, coherent theory of the universe. Basically, this means that signs of extra dimensions may reveal themselves in the way they impact gravitational waves.
“If there are extra dimensions in the universe, then gravitational waves can walk along any dimension, even the extra dimensions,” says Gustavo Lucena Gómez at the Max Planck Institute for Gravitational Physics in Potsdam, Germany.
Together with his colleague David Andriot, Gómez have tried to calculate how potential extra dimensions would affect the gravitational waves that we are able to observe. They found two peculiar effects: extra waves at high frequencies, and a modification of how gravitational waves stretch space.
Why gravity is so weak compared with the other fundamental forces has long been a subject of debate. Researchers suggest that some of the gravity is leaking away into extra dimensions beyond the three spatial dimensions we experience.
As gravitational waves propagate through a tiny extra dimension, the team found, they should generate a “tower” of extra gravitational waves with high frequencies following a regular distribution. Currently, we are unable to observe frequencies at that range, but we have technology to study the so-called breathing mode. Like your lungs as you breathe, space expands and contracts as gravitational waves pass through, in addition to stretching and squishing.
“With more detectors we will be able to see whether this breathing mode is happening,” says Lucena Gómez.
“Extra dimensions have been discussed for a long time from different points of view,” says Emilian Dudas at the École Polytechnique in France. “Gravitational waves could be a new twist on looking for extra dimensions.”
“It’s probably not a unique signature,” says Dudas. “But it would be a very exciting thing.”
Conclusive proof of extra hidden dimensions and evidence of parallel universe would undoubtedly be a major breakthrough in physics and cosmology. It could mean that faster-than-light travel might possible and our existing laws of the universe had to re-written.