Stephen Hawking showed a black hole constantly emits radiation that contains almost no information about its interior, causing the black hole to slowly evaporate. This suggests some information is irretrievably lost when the black hole dies. Theorists ever since have struggled to resolve the Hawking Information Paradox, which states information can neither be emitted from a black hole nor preserved inside it forever.
Based on Hawking’s calculations, the radiation and black hole are quantum mechanically linked, and this entanglement keeps rising until the black hole evaporates with quantum information. But theorists later determined the entanglement peaks when the black hole is massive and then drops to zero—so information can escape.
As part of this work, Berkeley Physics Assistant Professor Geoff Penington co-discovered “entanglement islands” sticking out of black holes, created when particles deep inside a black hole are reassigned to the radiation. Why this rearrangement occurs is a mystery, but entanglement islands may be the key to identifying how information escapes.
“Complementarity” theory hypothesizes information is stored in the black hole’s surface while also passing inside, creating two copies of information representing different viewpoints that can’t be simultaneously observed. “Firewall” theory hypothesizes everything falling into a black hole is incinerated by a physical firewall of energy surrounding an empty black hole, contradicting general relativity.
New research by Berkeley Physics Professor Raphael Bousso and Penington suggests entanglement islands protrude further than initially thought—as much as an atom beyond a black hole’s surface.
“Getting a scientific instrument within an atom’s width of a black hole horizon requires far more advanced technology than our current spaceships,” says Bousso. “But in principle we can tell which theory is correct by experimentally probing a black hole from the outside. This was a huge surprise.”
This is a reposting of my magazine research highlight, courtesy of UC Berkeley’s 2024 Berkeley Physics Magazine.
Image: Science Lab/Alamy
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