This is on the heels of the first ever verification of GR at the galactic scale. This time it is a test of GR's strong equivalence principle involving a neutron star and two white dwarfs (no, not the kind from that Snow White movie).[1]
Archibald and colleagues’ study breaks new ground because the gravitational energy inside a neutron star can account for as much as 20% of the body’s mass. The authors’ results therefore imply that the accelerations of gravitational energy and matter differ by no more than a few parts per 105 — a tenfold improvement over the bound from lunar laser ranging.
More importantly, the authors have provided what is known as a strong-field test of general relativity. Unlike the Solar System, for which Einstein’s theory predicts only small deviations from Newton’s theory of gravity, the motion of a neutron star in a gravitational field invokes full general relativity in all its complex glory. Einstein’s theory passes this strong-field test with flying colours.
The more they test it, the more convincing it becomes.
Zz.
[1] A.M. Archibald et al., Nature, 559, p73 (2018).
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