Avi Loeb

So they are sort of the signatures of a birth of a black hole that we see out of the collapse of a massive star.

So we do see a birth.

the births of black holes out of the collapse of massive stars.

And we know, for example, in the Milky Way galaxy, there are about 10 million such black holes, stellar mass black holes.

We also see them in gravitational waves when you have two such black holes in a pair, and they are close enough together so that they create ripples of space-time that we can detect from a distance.

According to Einstein's gravity, when you have a single object, it curves spacetime.

But when you have two objects moving around, they create ripples.

These are called gravitational waves.

And they propagate outwards.

It's as if you move a stick on the surface of a pond and it creates those waves propagating out.

So in the same way, we could potentially detect the gravitational waves from an emerging pair of black holes.

We did detect that in 2008.

That was exactly a century after Einstein came up with his theory of gravity.

Einstein would have been delighted to see.

He thought at some point that gravitational waves do not exist, but now we detected them and the Nobel Prize was given for that detection of two black holes coming together, stellar mass black holes coming together

And they were detected not by light, but by gravitational waves.

Completely new method in astronomy.

And there is another probe.

I mean, this was done by laser interferometers on Earth.

The discovery was done by the LIGO experiment that was funded by the National Science Foundation in the U.S.,