Testing the black hole area law with Event Horizon Telescope

Abstract: Hawking's black hole area theorem can be tested by monitoring the evolution of a single black hole over time. Using current imaging observations of two supermassive black holes M87* and Sgr A* from the Event Horizon Telescope (EHT), we find their horizon area variation fractions are consistent with the prediction of the black hole area law at the $1\,\sigma$ confidence level. We point out that whether the black hole area law is valid or not could be determined by future high precision EHT observations of Sgr A*.