Professor Stephen Hawking moved an audience to tears on Sunday, after he spoke at an event to mark his 75th birthday.
The physicist and cosmologist gave a talk reflecting on his life and scientific work during a public symposium at Cambridge University.
Prof Hawking, who turned 75 in January, joked: “Actually, for those keeping count, I’m closer to 75-and-a-half. But that shouldn’t get in the way of a good celebration.”
In his talk, titled My Life In Physics, he spoke about his early realisation of his medical problems when he went skating with his mother, according to Cambridge News .
“I fell over and had great difficulty getting up,” he said.
Prof Hawking was later diagnosed with amyotrophic lateral sclerosis (ALS), at the age of 21.
“At first I became depressed,” he said. “I seemed to be getting worse really rapidly.
“There didn’t seem any point working on my PhD because I didn’t know I would live long enough to finish it.
“But then the condition developed more slowly and I began to make progress in my work.
“After my expectations had been reduced to zero, every new day became a bonus and I began to appreciate everything I did have. While there’s life there’s hope.”
After flying through his world-shattering achievements in physics and beyond with a humbling modesty, Prof Hawking finished on a very human note.
He said: “Our picture of the universe has changed a lot in the last 50 years and I am happy if I have made a small contribution.
“Remember to look up at the stars and not down at your feet. Be curious and however difficult life may seem, there is always something you can do and succeed at.”
His speech followed an afternoon of lectures about gravity and black holes from other distinguished scientists, including Professor Brian Cox.
The Cambridge-based rock star physicist was the first to address the audience, with a whistle-stop tour of the history of the universe, along with our developing understanding of it.
Although Professor Cox credited Mr Hawking with inspiring him to study physics, he said it was Hawking’s engagement with the public that was his greatest achievement.
“I think one of the reasons we are celebrating Stephen’s birthday this way is not only because of his great contribution to physics but due to his great contribution to the public understanding of science,” he said.
The event concluded with the full auditorium singing Happy Birthday to Prof Hawking.