The existence of parallel universes has long been one of the biggest mysteries of the universe.
Now, scientists believe they have found a way to some day detect hidden dimensions.
Physicists think that unknown dimensions could cause ripples through reality by modifying gravitational waves – changes in the space-time fabric.
And since gravity is likely to occupy all dimensions that exist, its waves are a promising way to detect unknown dimensions.
While we are aware of the three dimensions that surround us on a daily basis – length, width and depth – physicists have long believed that there may be more.
In the hopes of understanding whether another dimension does exist, researchers from the Max Planck Institute for Gravitational Physics in Potsdam are looking at gravitational waves – ripples in space-time, caused by the motion of massive objects.
Gravity is weaker than other fundamental forces, and experts have long wondered whether this is because some of it is escaping into an extra dimension.
Speaking to New Scientist, Gustavo Lucena Gomez, who is leading the study, said: ‘If there are extra dimensions in the universe, then gravitational waves can walk along any dimension, even the extra dimensions.’
The researchers set out to calculate how an extra dimension would affect gravitational waves, and found two strange effects – extra waves at high frequencies, and a change in how gravitational waves stretch space.
As gravitational waves move through an extra dimension, the researchers found that they should generate a ‘tower’ of extra gravitational waves with higher frequencies.
But observatories are currently unable to detect frequencies that high, and instead focus on lower frequency gravitational waves.
This could make spotting the gravitational wave towers a challenge.
But detecting the change in how gravitational waves stretch space could be easier, according to the researchers.
Dr Lucena Gomez said: ‘If extra dimensions are in our universe, this would stretch or shrink space-time in a different way that standard gravitational waves would never do.’
Gravitational waves stretch space as they ripple through the universe a bit like a rubber band – the ellipse gets longer in one direction and shorter in the other, before returning to its original shape.
But an extra dimension could add another way for gravitational waves to stretch space, called a breathing mode.
In the same way that lungs expand as you breathe, gravitational waves cause space to expand and contract, in addition to stretching.
Dr Lucena Gomez said: ‘With more detectors we will be able to see whether this breathing mode is happening.’
Dr Emilian Dudas, from the Ecole Polytechnique in France told New Scientist: ‘Extra dimensions have been discussed for a long time from different points of view.
‘Gravitational waves could be a new twist on looking for extra dimensions.’