Israeli academic inspired one of Stephen Hawking’s biggest discoveries
Scientist Jacob Bekenstein, who later taught at Hebrew University for 25 years, sparred with preeminent theoretical physicist before they cooperated on black holes In the early 1970s, when the British-born Hawking had already done essential work on the cosmic gravitational fields known as black holes, he got into a disagreement with Jacob Bekenstein, then a doctoral student at Princeton. Bekenstein, the son of Polish-Jewish parents in Mexico, had Israeli citizenship and went on to teach at the Hebrew University in Jerusalem for 25 years.
In his doctoral thesis, which made waves in 1972, Bekenstein theorized that black holes had entropy, or disorder in their system, and subsequently, according to the laws of physics, a temperature. Hawking disagreed, maintaining that black holes could not radiate anything and therefore had no temperature. At a conference in France that year, Hawking gathered a few colleagues and angrily confronted Bekenstein. “These three were senior people. I was just out of my Ph.D. You worry whether you are just stupid and these guys know the truth,” Bekenstein said about the event.
But in 1974, Hawking proved Bekenstein’s idea through a complicated quantum theory calculation. At first he kept the calculation secret, afraid to admit his mistake. He eventually made his discovery public — today it is considered one of his most important achievements. Today, the entropy of a black hole is called Bekenstein-Hawking entropy, but the radiation emitted from a black hole is called Hawking-Bekenstein radiation, or often just Hawking radiation. That might seem unfair, but it’s a necessary distinction, as Bekenstein said himself. “The entropy of a black hole is called Bekenstein-Hawking entropy, which I think is fine. I wrote it down first, Hawking found the numerical value of the constant, so together we found the formula as it is today,” he said. “The radiation was really Hawking’s work. I had no idea how a black hole could radiate. Hawking brought that out very clearly. So that should be called Hawking radiation.”
Some believed Bekenstein, who wore a kippah and won Israel’s prestigious Wolf Prize in 2012, should have won the Nobel Prize for his contributions to science (the prize is not awarded posthumously). But his work and connections to Hawking live on: Hawking said he wanted the Bekenstein-Hawking entropy equation engraved on his tombstone.