http://www.space.com/33176-gravitational-waves-from-second-black-hole-collision.html
LIGO scientists waited until now to announce the second detection because they had to make sure that it was real, and that it was caused by a black hole collision, team members said.
Scientists wanted to make certain that the second gravitational wave was caused by colliding black holes.
What else could have caused a gravitational wave the scientists aren't telling us about?
LIGO scientists waited until now to announce the second detection because they had to make sure that it was real, and that it was caused by a black hole collision, team members said.
Scientists wanted to make certain that the second gravitational wave was caused by colliding black holes.
What else could have caused a gravitational wave the scientists aren't telling us about?
