Of the celebrity cast, Hawking was the only one who diverted the social media titan's attention to science, asking him:
"I would like to know a unified theory of gravity and the other forces. Which of the big questions in science would you like to know the answer to and why?"
Zuckerberg responded with a few predictable topics including how to cure all diseases and how the brain works.
However, at the top of his list was a Peter Pan-esque question that science has yet to answer: "what will enable us to live forever?"
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Keen to keep the world of social at the fore front of his answers, he also added:
"I'm also curious about whether there is a fundamental mathematical law underlying human social relationships that governs the balance of who and what we all care about. I bet there is."
Obviously if science ever calculated this, things would be smooth sailing for Facebook.
The Q&A also touched on the company's unerring expedition into the world of artificial intelligence.
Zuckerberg frankly stated: "our goal is to build AI systems that are better than humans at our primary senses: vision, listening, etc."
Facebook are in fact well on their way to delivering this. In June, the company's artificial intelligence lab unveiled an algorithm that is able to recognise people in photos using only the back of their heads.
The whole thread of questions was based on the assumption that Facebook will live forever -- a point highlighted by community member Aakash Chaudhary, who asked: "how will you react if you woke up next morning and there is no Facebook?"
Zuckerberg's answer is surprisingly simple: