LONDON — Physicist Stephen Hawking says he would consider ending his life if he felt he had nothing more to contribute or had become a burden to those around him.

The 73-year-old Cambridge professor, who has a form of motor neurone disease, made the comments in an interview with Dara Ó Briain for a forthcoming BBC One documentary.

"I would consider assisted suicide only if I were in great pain or felt I had nothing more to contribute but was just a burden to those around me," Hawking said, according to the Daily Telegraph. However, he added: "I am damned if I'm going to die before I have unravelled more of the universe.”

Hawking said that to keep someone alive against their wishes is the ultimate indignity.

Dara O Briain meets Stephen Hawking Image: BBC Dara O Briain meets Stephen Hawking

The physicist and cosmologist changed his stance on assisted suicide in 2013 in an interview with the BBC when he said people with a terminal illness who are in great pain should have the right to choose to end their lives. He had said some years earlier that assisted suicide was a "great mistake" and "while there's life, there is hope."

Assisted suicide is illegal in England and, depending on the circumstances, can be punishable by up to 14 years in prison. Earlier this week Lord Falconer, who has sponsored a private member's bill aimed at giving terminally ill patients the right to die, urged the government to make time available to discuss it. Last week, the Scottish assembly defeated an assisted dying bill by 82 votes to 36.

In the wide-ranging interview with Hawking, which will be broadcast on June 15, he also talked about being lonely.

“At times I get very lonely because people are afraid to talk to me or don't wait for me to write a response,” he said. “I'm shy and tired at times. I find it difficult to talk to people I don't know."