Science › Black holes & quantum gravity
Jacob Bekenstein
1972· Person
ProvenTested many times; part of working physics.
Mexican-born Israeli-American physicist (1947–2015), Hebrew University, who first argued black holes have entropy.
See it on the Science map →How it works
As a Princeton graduate student under John Wheeler in 1972, Bekenstein asked what happens to the disorder (entropy) of hot material thrown into a black hole. If it simply vanished, the second law of thermodynamics would fail. He proposed that the black hole itself carries entropy, proportional to its horizon area. Leading experts, including Hawking, initially thought this was wrong because it implied black holes have a temperature.
Why it matters
His idea opened the field linking gravity, information and thermodynamics, and led directly to Hawking radiation and the holographic principle.
How the work held up
Hawking's 1974 calculation confirmed his proposal and fixed the exact number. String theory reproduced it in 1996 for special black holes. He received the Wolf Prize in 2012.
Still a mystery
His "Bekenstein bound" on how much information any region can hold is widely accepted but not fully proven in general.
Connections (2)
▸Jacob Bekenstein proposed Black-hole entropy: information on the surfaceWell supported
The relationship
John Wheeler posed a puzzle: drop a cup of hot tea into a black hole and its entropy seems to vanish, breaking the second law of thermodynamics. Bekenstein proposed that the black hole gains entropy as it grows, proportional to its horizon area. Then total entropy, ordinary plus black hole, never decreases. He called this the generalized second law.
How the link was found
Jacob Bekenstein, Princeton PhD student of Wheeler, in 1972, with a fuller paper in 1973. Hawking and others initially rejected it.
Is it proven?
Hawking's 1974 discovery that black holes have a temperature made the idea consistent. String theory's 1996 count of black-hole states matched it for special cases.
Open questions and mysteries
Whether the generalized second law holds in all situations, including quantum ones, is mostly but not completely proven.
▸Jacob Bekenstein tied black holes to Information is physicalWell supported
The relationship
Bekenstein argued that a black hole must have entropy, proportional to its horizon area, or else throwing hot gas into one would destroy entropy and break thermodynamics. Entropy here means hidden information. So information has a physical home and a maximum density, a concrete case of information being physical.
How the link was found
Jacob Bekenstein, as John Wheeler's graduate student at Princeton, in 1972-73. He later proposed the Bekenstein bound (1981) on information in any region.
Is it proven?
Stephen Hawking, initially skeptical, confirmed it in 1974 by showing black holes radiate with a temperature. Hawking radiation has not been observed directly.
Open questions and mysteries
What microscopic states make up black-hole entropy in our universe is unknown, though string theory counted them for special cases in 1996.