The no-hair theorem, which says that black holes only have three defining properties, has been tested in a new analysis of the first-ever gravitational waves to be detected.
Maximiliano Isi at the Massachusetts Institute and colleagues in New York and California looked at the “ringdown” signal from the GW150914 merger of two black holes and have shown that it is consistent with the theorem.
The no-hair theorem is the statement that a black hole is characterized by only three observable properties – its mass, angular momentum and electrical charge. “No hair” refers to the resemblance of a black hole to a bald head with few defining features. While the theorem has no rigorous mathematical proof, it is in line with general relativity and therefore widely accepted.
The theorem is also at the centre of an important paradox of modern physics regarding whether information is destroyed when something is sucked into a black hole. The no-hair theorem suggests that information must be destroyed, whereas quantum theory says otherwise. As a result, understanding whether the no-hair theorem is correct has important implications beyond black holes.
This latest test of the theorem uses data from September 2015, when the LIGO gravitational-wave ...