A top Israeli professor has paid tribute to Stephen Hawking following his death, as he recalled how a debate with between the British academic and a Jerusalem physicist led to a breakthrough theory on the thermodynamics of black holes.

Barak Kol, who heads Hebrew University (HU)’s Racah Institute of Physics, spoke about Hawking’s debate with Jacob Bekenstein, a HU physicist, which led to the groundbreaking change in thought.

Paying tribute to the scientist, Kol said: “We in Israel, like all over the world, were saddened by the news.

“Hawking was one of the leading scientists of our time, and also a great human being. Struggling with his illness in a way that let him lead a meaningful life, that’s what made him a celebrity and someone who was known in every household.”

Prof. Barak Kol

Kol met Hawking several times, adding that the time it took for him to reply meant communication was usually one-way, either by listening to a pre-prepared lecture of his, or by him listening in to the scientific conversation of others.

“Hawking was known for his contributions on Einstein’s theory of gravity, black holes and cosmology, to the very beginning of the universe, and quantum mechanics, but his single most important contribution was on the radiation of black holes,” said Kol.

When he met Bekenstein in the 1970s, Kol said, the two debated. “Before then, we thought nothing could escape from a black hole, not even light,” said Kol. “But Bekenstein showed that black holes had what I’ll call ‘heat,’ in other words that they were cold but not freezing, as you might expect.”

Picture of Jacob D. Bekenstein in his office at the Hebrew University in Jerusalem

Hawking initially opposed Bekenstein’s idea on the grounds that a black hole could not radiate energy and therefore could not have entropy, but in 1974, the British don recalculated and aw that particles could in fact emit from black holes.

Hawking, who visited Israel four times, was known for his support for the Palestinians and in 2013, drew Israeli anger for his decision to join the academic boycott of Israel.

The physicist cancelled his participation in a Jerusalem conference sponsored by then-president Shimon Peres, according to Times of Israel.

“I accepted the invitation to the Presidential Conference with the intention that this would not only allow me to express my opinion on the prospects for a peace settlement but also because it would allow me to lecture on the West Bank,” Hawking wrote in a letter at the time.

Hawking also encouraged support for investment in Palestinian science in 2017.