Andrew Strominger

is described just by its mass and spin.

They can also rotate, as was later shown by Kerr.

And this is very much unlike a star, right?

Every star of the same...

mass is different in a multitude of different ways.

Different chemical compositions, different motions of the individual molecules.

Every star in the universe, even of the same mass, is different in many, many different ways.

Black holes are all the same.

And that means when you throw something in Einstein's description of them, which we think must be corrected.

And if you throw something into a black hole, it gets sucked in.

And if you throw in a red book or a blue book, the black hole gets a little bigger, but there's no way within Einstein's theory of telling how they're different.

And that was one of the assumptions that Hawking made in his 1974, 75 papers in which he concluded that black holes destroy information.

You can throw encyclopedias, thesis defenses, the Library of Congress.

Yeah.

So what Hawking and I showed, and also Malcolm Perry, is that one has to be very careful about what happens at the boundary of the black hole.

And this gets back to something I mentioned earlier about when two things which are related by a coordinate transformation are and are not equivalent.

And what we showed is that there are very subtle imprints when you throw something into a black hole.

There are very subtle imprints left on the horizon of the black hole, which you can read off at least partially what went in.

And so this invalidates Stephen's original argument that the information is destroyed.

That's the soft hair, right.