The Breakdown of Classical Gravity?
(17 votes over all institutions)
Assuming Newton’s gravity and GR to be valid at all scales, leads to the dark matter hypothesis as a forced requirement demanded by the observed dynamics and measured baryonic content at galactic and extra galactic scales. Alternatively, one can propose a contrasting scenario where gravity exhibits a change of regime at acceleration scales $a<a_{0}$, and obtain just as good a fit to observations across astrophysical scales. A critical experiment in this debate is offered by wide orbit binary stars. Since for $1 M_{\odot}$ systems the acceleration drops below $a_{0}$ at scales of around 7000 AU, an statistical survey of relative velocities and binary separations reaching beyond $10^{4}$ AU should yield a conclusive answer to the above debate. By performing such a study we show Kepler's third law to fail precisely beyond $a \approx a_{0}$ scales, precisely as predicted by modified gravity theories designed not to require any dark matter at galactic scales and beyond.
