The cosmic force of gravity has been a hot topic the last few years thanks to a few big Hollywood movies. Two recent studies, though, may have delivered a blow to the theories surrounding extra dimensions that we can’t see, but that gravity may penetrate. The film Interstellar explores one such concept: that the gravitational forces behind a black hole which would potentially reveal some key insight into the theory of gravity. Large scale experiments are done through observation of cosmic phenomena, but we do have the ability to test some of these theories about gravity by shrinking things down to the smallest of scales.
Chinese researchers used a torsion pendulum to detect possible variations in gravitational forces. Using the torsion pendulum with an opposite attractor, the idea was to use the attractor to act upon the pendulum through its gravitational force. Any change in the oscillating rate needed to swing the pendulum would indicate potential loss of gravitational energy to extra dimensions. However, once they engaged the attractor opposite of the pendulum, they found no change in the gravitational signal, indicating that there were no extra dimensions with gravitational significance acting on the model. But what about at the atomic level you say?
Enter stage left, the Large Hadron Collider (LHC).
Using the LHC, physicists hope to discover proof of the string theory, among others, by colliding atomic particles and visualizing the building blocks of the universe. There are several ways they hope to glimpse the possibility of these extra dimensions. One way could be an unbalanced loss of energy during a collision that could signify the transfer of the theoretical graviton particle into an extra dimension. Another way would be the detection of microscopic black holes. Several theorists are using the theory of gravity’s rainbow to explain why the LHC has been unable to produce the events at the levels previously thought that they would appear. So, perhaps in the near future we will still see a change to the inverse-square gravity relation and the four dimensions we perceive.
Large scale observations of cosmic phenomena seem to be confirming the reign of the four dimensions as well. A recent event witnessed by astrophysicists, where two neutron stars collided, allowed them to observe light and gravity over large spatial dimensions. Astrophysicists were able to detect the event using the light waves it emitted. Following the gravitational waves, they then measured for any loss of gravitational energy, but found that the wave strength held steady in relation to its distance from Earth. If gravity did interact and bleed through to large extra dimensions then there would have been a weakening of the observed gravitational waves. Chalk one up to Einstein and General Relativity as gravity does not seem to be playing a role with large extra dimensions.