Science › Black holes & quantum gravity
The Page curve and "islands": information escapes
2019· Theory
SpeculativeA serious idea with no experimental proof yet.
The predicted rise-then-fall of a black hole's hidden information, recently reproduced in calculations using inside regions called "islands".
See it on the Science map →How it works
In 1993 Don Page showed that if information escapes, the radiation's entanglement with the black hole must grow, then peak around the halfway point of evaporation, then fall to zero. Hawking's original calculation only grows. In 2019 several groups found that by counting a region inside the black hole, an "island", as part of the radiation, ordinary gravity calculations reproduce Page's falling curve.
Why it matters
It is the first gravity calculation showing information can come out, strongly suggesting Hawking's 1976 conclusion was wrong.
How we know
Mathematical results by Penington; Almheiri, Engelhardt, Marolf and Maxfield (2019), and "replica wormhole" papers (2019–2020). Done mostly in simplified model universes. No experiment.
Still a mystery
It shows that information comes out, not how. Whether it holds for real black holes in our universe is unclear.
Connections (2)
▸The black-hole information paradox has recent progress in The Page curve and "islands": information escapesSpeculative
The relationship
If information escapes, the radiation's entanglement with the black hole must follow the Page curve: rising early, then falling back to zero as evaporation completes. Hawking's method gave only a rising line. Newer calculations count a region inside the black hole, the "island," as part of the radiation and recover the falling curve, showing information can leave.
How the link was found
Don Page predicted the curve in 1993. In 2019 Geoff Penington, and separately Almheiri, Engelhardt, Marolf and Maxfield, reproduced it; "replica wormhole" papers (2019–2020) explained why.
Is it proven?
These are mathematical results, mostly in simplified model universes, using well-understood gravity. They are strong evidence that information survives, but not experimental proof.
Open questions and mysteries
The calculation shows the bookkeeping balances but not the physical mechanism that carries information out.
▸The Page curve and "islands": information escapes relies on The holographic principleSpeculative
The relationship
The Page curve tracks how much information leaks out of an evaporating black hole over time. The 2019 calculations that finally reproduced it used holographic tools: rules relating entanglement to surface areas, first worked out within AdS/CFT. They found hidden "islands" inside the black hole that count as part of the outside radiation.
How the link was found
Don Page described the curve in 1993. In 2019 Geoff Penington, and separately Almheiri, Engelhardt, Marolf and Maxfield, derived it using holographic entanglement methods.
Is it proven?
The calculations are consistent and were confirmed by several groups, but in simplified model universes, often lower-dimensional or anti-de Sitter. No observation tests them.
Open questions and mysteries
Whether the method works for realistic black holes in our universe, and what islands physically mean, are open.