# Physics Colloquium

*,*UC Berkeley

*,*

Limited attendance open to first 100 attendees. Valid Caltech ID required for in person attendance in Feynman Lecture Hall, 201 E. Bridge. Join via Zoom

https://caltech.zoom.us/j/89237465190

Meeting ID: 892 3746 5190.

In the 1970s, Hawking showed that black holes are finite-temperature objects that radiate energy and eventually evaporate away entirely. However, his calculations suggested something very weird: that, unlike any other physical system, this radiation contained no information about the initial state of the black hole. Information that fell into the black hole appeared to be lost forever. This contradiction between Hawking's calculations and the ordinary rules of quantum mechanics has been a driving force behind much of the research in quantum gravity over the ensuing decades. Finally, in the last couple of years, we have begun to understand where Hawking's calculation went wrong, and to derive precise predictions, consistent with unitary quantum mechanics, for the information content of Hawking radiation. However, the new calculations, which involve weird spacetime topologies called 'spacetime wormholes', lead to as many new questions as answers...