HEAPOW: Leaking Gravity? (2018 Feb 05)
Why is gravity such a weak force, the weakest by far of the four fundamental forces? One possible explanation is that gravity may have access to other physical dimensions beyond the three spatial dimensions we know and love, and that gravity can leak into these other dimensions, weakening the residual force we observe in our three-dimensional world. If true, this might indicate that gravity works differently over very long and relatively short distances. Astronomers can actually put limits on this leakage by looking at the behavior of gravitational waves produced by sources at known distances. Nature has kindly provided one such source (so far), the now-famous merger of two neutron stars which was observed on August 17, 2017. This event (shown in the illustration above) is important because it both generated gravitational radiation and also produced an electromagnetic signature in Gamma-rays (and ultraviolet, optical and X-ray radiation) which allowed astronomers to pinpoint its location and determine its distance from us. Based on the how the gravitational waves generated by this neutron star merger spread out with distance, astronomers have found no evidence of any leakage of gravity into extra dimensions. This re-assuring result shows that the number of spatial dimensions on length scales of kilometers is limited to the familiar three.
Science News: Gravity doesn’t leak into large, hidden dimensions
Limits on the number of spacetime dimensions from GW170817 - Kris Pardo et al
- arXiv.org > gr-qc > arXiv:1801.08160 > 24 Jan 2018
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