What Black Holes Are“This is the clearest view yet of the nature of black holes,” says Isi, who is also an assistant professor at Columbia University. “We’ve found some of the strongest evidence yet that astrophysical black holes are the black holes predicted from Albert Einstein’s theory of general relativity.”Black holes are the final stage of stellar evolution, when a star’s mass collapses in on itself to create a density so powerful that even light cannot escape. These new, more precise readings, combined with the innovative method, allowed the team to isolate the merger from the final black hole as never before. “Ten milliseconds sounds really short, but our instruments are so much better now that this is enough time for us to really analyze the ringing of the final black hole,” Isi says. “It’s really profound that the size of a black hole’s event horizon behaves like entropy,” Isi says.