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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 renowned British physicist, who died at 76, left behind a riddle that could eventually lead his successors to the theory of quantum gravity.
The amount of energy infusing empty space seems too small to explain without a multiverse. But physicists have at least one alternative left to explore.
A recently proposed experiment would confirm that gravity is a quantum force.
The theoretical physicist Joe Polchinski, who died Feb. 2, left a tremendous professional and personal legacy, says a friend and collaborator.
Cosmologists have shown that it’s theoretically possible for a contracting universe to bounce and expand. The new work resuscitates an old idea that directly challenges the Big Bang theory of cosmic origins.
For decades, physicists have struggled to create a quantum theory of gravity. Now an approach that dates to the 1970s is attracting newfound attention.
A complete classification could lead to a wealth of new materials and technologies. But some exotic phases continue to resist understanding.
The mother of all string theories passes a litmus test that, so far, no other candidate theory of quantum gravity has been able to match.