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5 live listener Matthew once wrote to Stephen Hawking in 1990, looking for an answer to a question he and his friend had.

He received a response from the physicist, who cleared up the debate with a letter.

Matthew still has the letter to this day and read it out during 5 live's 'Your Call', after the news that Hawking died peacefully at home aged 76.

This clip is originally from 5 live's Your Call, 14 March 2018.