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Gravitational waves have opened up new ways to test the properties of black holes — and Einstein’s theory of gravity along with them.
The theoretical physicist Joe Polchinski, who died Feb. 2, left a tremendous professional and personal legacy, says a friend and collaborator.
Simple math shows how widespread vaccination can disrupt the exponential spread of disease and prevent epidemics.
For decades, physicists have struggled to create a quantum theory of gravity. Now an approach that dates to the 1970s is attracting newfound attention.