Extra dimensions are a favorite plot device within the science-fiction genre, but they might not have a basis in reality, at least according to a new analysis of the breakthrough gravitational wave data recently collected from the LIGO experiments, reports Phys.org.
Gravitational waves are disturbances in the fabric of spacetime, and they are so subtle that it takes massive, cataclysmic events to make waves large enough for us to detect. In fact, until recently, gravitational waves were, like extra dimensions, entirely theoretical. That all changed when LIGO (Laser Interferometer Gravitational-Wave Observatory) first detected them back in 2015. Analyzing the data from these detections has led to new insights into the nature of the universe that scientists are only just beginning to unravel.
One such insight? There's no evidence that any extra dimensions exist within our universe, besides the four that we know of: three spatial dimensions and the fourth dimension of time. That might mean theorists will need to go back to the drawing board when it comes to explaining some of the bigger mysteries that still abound about the cosmos.
A dark energy theory, blown
For instance, one such mystery is that of "dark energy," the strange force that's making the universe expand faster and faster. One popular theory to explain dark energy relies on the existence of extra dimensions, wherein some of the gravity that we observe in the universe "leaks." If these extra gravity-draining dimensions did exist, that might cause gravity to get weaker over large distances, and this might explain why the universe is expanding faster the further we look.
But so far, it doesn't appear that this theory will hold up. All of the gravitational waves that we've detected so far match our expectations about the strength of gravity, even gravity that's been stretched over hundreds of millions of light-years. If extra dimensions do exist, they aren't stealing any of the gravity from our garden-variety four known dimensions.
That's a bit of a bummer for our science-fiction fantasies, but it's how science moves forward. Even if there are no extra dimensions, there are still mysterious phenomenon, like dark energy, that need explaining. And who knows what other fantastical ideas might turn out to be true in our search for answers.