Dara O Briain fell in love with the night sky in decidedly unglamorous circumstances. He became besotted with stargazing the moment he was ordered to put the bins out one evening as a teenager in Ireland.
"As soon as I stepped out of the front door that night, I looked up, saw the Plough for the first time and thought, 'Wow! That's incredible!' Then when I saw it again on holiday, I thought, 'There it is again!' I realised the Plough was everpresent. I got this astonishing sense of its eternity. I was immediately hooked."
O Briain, 39, who studied mathematics and theoretical physics at University College Dublin, rekindles his passion over three nights this week with fellow astro-head Brian Cox for BBC2's Stargazing Live. Stretching out his long limbs on a sofa in a west London photographic studio and sipping from a bottle of Diet Coke, the comedian explains why he is so smitten by the stars.
"Astronomy sparks the imagination," he says. "One of the great universal sources of wonder is just to tilt your head back and gawp at this incredible show unfolding above you.
"It also gives you an amazing sense of perspective. Looking up at the stars makes us realise that we are nothing. And there is nothing wrong with the odd injection of perspective in our lives."
This innate sense of wonder helps explain why Stargazing Live attracted almost four million viewers when it was first shown last year, he says. The other reason behind its popularity is, of course, O Briain's stratospherically popular co-host.
"The Brian Cox Effect is massive. People may witter on about Brian's hair and his dreamy eyes - and he does, of course, have them - but the viewers who are simply swooning over him tend to miss the fact that his programmes are fantastic. Brian has found an audience hungry for something that has substance to it. His programmes have tremendous heft."
O Briain jokes that he has been able to offer Cox some solid career advice. "We were in a bar in Soho one night, and I told Brian the first rule of showbiz: What would David Attenborough do?
"Nothing with the word 'celebrity' in the title, nothing involving eating kangaroo parts in the jungle, and no hosting light-hearted quiz shows. Of course, I don't have to live by those rules myself! I'm still living by: What would Dave Allen do? But Brian's stuff has proper weight."
This time round, Stargazing Live again comes from Jodrell Bank and will train its telescope on several different aspects of the universe. It will, for example, explore the malign influence of light pollution on astronomy by blacking out a whole village in Devon. The Milky Way, alien life and the search for a new planet outside our solar system are also on the agenda.
"We will also be looking at the fact that we are in a constant struggle with the Moon. It's locked into a permanent position so we never see the dark side of the Moon. Hey, that's a great phrase - it could have legs!"
The comedian traces his love of science back to an inspirational teacher, saing: "When I was 14, my science teacher told me about the theory of relativity for the first time. He dangled a few of the most enticing results in front of me, and I started to devour books such as In Search of Schrödinger's Cat and A Brief History of Time. I ended up doing a degree in science."
Now O'Briain is a terrific popular advocate for science - "even though I studied it and then ran away to join the circus! Science is a tough old degree, and I didn't think I could work in that field. But I have underlying admiration for people who do. Working a science degree up into a career is a thankless task. You could never describe my career as thankless - I get thanked every 15 seconds!"
The contagious passion of people such as Cox and O Briain has helped stimulate the general public's interest in science.
"This is a moment of huge enthusiasm for science. In comedy, there is a big push towards people arguing on behalf of rational thought and a great reaction against things that have no basis in reason.
"Alongside art, science is one of the two great castles of human knowledge, and a lot of people who have a hunger for it were being underserved. But why should we be scared of smartness? People get a genuine rush from learning something they didn't know before. Give people credit for having curiosity - one of the basic human virtues - and they'll thank you for it."
So what does he hope that viewers will take away from this series?
"If they discover one thing that nestles in their head, that would be brilliant. People assume that a lot of things on TV are faked these days. But what made the last series for me was that everything was absolutely genuine. In the opening moments of the show, I said to the astronomer at Jodrell Bank, 'What have we got?' and he replied, 'We've got Jupiter.'
"There was a beat, and as I looked through his telescope, I thought, 'Jeez, we really have got Jupiter. That's amazing!' That was a genuine 'Wow!' moment. The planet was actually there, clearly visible through the telescope. It was not filmed in a zoo in Holland!"
His proselytising for science does not end with Stargazing Live. He has just filmed another programme that he hopes will broaden the appeal of science. "I've done a maths show with Marcus du Sautoy. It's called Dara O Briain's School of Hard Sums. Marcus sets a problem, and I have to stand at a blackboard and find an elegant mathematical solution to it.
"I did think, 'How televisual is it to watch me scribbling furiously on a blackboard?' But when I got it right, it was the most genuinely exciting moment of my TV career. It was much more exciting that the fake happiness of, 'Oh, we did better than David Mitchell's team this week.'
"You may think, 'Ruddy hell, what's that about?' It could be really good, or the strangest, most career-ending gamble ever. 'Whatever happened to Dara O Briain? The last I saw of him, he was doing maths for cash!'"
The final part of Stargazing Live airs tonight, 8pm, BBC2/BBC HD.