115 | Netta Engelhardt on Black Hole Information, Wormholes, and Quantum Gravity

Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas

Sean Carroll | Wondery

Society & Culture, Physics, Philosophy, Science, Ideas, Society

4.8 • 4.4K Ratings

🗓️ 21 September 2020

⏱️ 87 minutes

🔗️ Recording | iTunes | RSS

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Summary

Stephen Hawking made a number of memorable contributions to physics, but perhaps his greatest was a puzzle: what happens to information that falls into a black hole? The question sits squarely at the overlap of quantum mechanics and gravitation, an area in which direct experimental input is hard to come by, so a great number of leading theoretical physicists have been thinking about it for decades. Now there is a possibility that physicists might have made some progress, by showing how subtle effects relate the radiation leaving a black hole to what’s going on inside. Netta Engelhardt is one of the contributors to these recent advances, and together we go through the black hole information puzzle, why wormholes might be important to the story, and what it all might teach us about quantum gravity.

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Netta Engelhardt received her Ph.D. in physics from the University of California, Santa Barbara. She is currently on the faculty in the physics department at MIT. She recently shared the New Horizons in Physics Prize with Ahmed Almheiri, Henry Maxfield, and Geoff Penington, “for calculating the quantum information content of a black hole and its radiation.”

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Transcript

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0:00.0	Hello everyone, welcome to the Winescape Podcast. I'm your host Sean Carroll. For those of you who are physics fans out there
0:06.4	You will know that one of the very long-standing big picture puzzles in physics is quantum gravity
0:14.0	reconciling Einstein's general theory of relativity
0:16.8	Which is a theory of gravity with the fundamental principles of quantum mechanics and a problem with this puzzle is that we don't have a lot of
0:24.9	experimental guidance in fact the only experimental guidance we have is that classical
0:30.2	General relativity seems to work very well and quantum mechanics seems to work very well
0:34.5	So there's somehow going to be reconciled someday something we do have though our thought experiments
0:40.9	Which can help guide us in thinking about well if we do eventually
0:45.6	Managed to quantize gravity what will it look like what shape will it have what will it teach us what will be the
0:52.8	Fundamental ingredients and the most important thought experiment we have is the black hole
0:58.0	Information loss puzzle. This is something that was given to us by Stephen Hawking who in the 1970s showed that black holes
1:04.5	Aren't completely black when you include quantum mechanics they radiate and eventually they'll evaporate completely away
1:10.9	into
1:11.9	essentially information-free
1:14.6	thermal radiation
1:16.2	The puzzle is that most of physics doesn't work like that most of physics
1:21.4	Conserves information even if you throw a book into a bonfire
1:25.5	The information in the book is somehow we think encoded in all the heat and light that is made in the process of burning the book
1:33.5	Whereas if Hawking were right then black holes are different they destroy the information that gets thrown into them
1:40.1	A lot of us don't believe that's actually the right answer
1:42.9	We believe that the calculation that Hawking did has been incomplete
1:47.3	But it's very very hard as it turns out to figure out mechanisms that can somehow get the information out
	...

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