TV's sexiest scientist and his Uncaged Monkeys co-star on whether hardened rationalists should really celebrate the birth of Jesus, and the pressie-distribution powers of Santa

Brian Cox may be best known as the anorak-wearer who trots the globe at the BBC's expense gawping at stars, but for the next month he's teaming up with stand-up comic Robin Ince for a run of live shows celebrating the wonder of science.

The idea for their Uncaged Monkeys shows originally came from Ince. "I wanted for a long time to do spectacular shows about science. I believed there was an audience that wanted to come to a show and then leave with a reading list," he says.

For Cox, playing theatres is very different to filming one of his TV spectaculars, "but Robin does it in a very glamorous way, insisting on us having the finest hotels, so it's actually far more luxurious than working for the BBC."

The pair will be accompanied by professor Simon Singh and the Guardian's own Dr Ben Goldacre, whom Cox describes as "more extreme with his behaviour than any rock star. He makes Jimmy Page look like a pussycat."

Following the short tour, the pair will be holing up at London's Bloomsbury Theatre for the seemingly annual Nine Lessons And Carols For Godless People, a Christmas celebration for rationalists that in the past has featured contributions from Jarvis Cocker, Ricky Gervais and professor Richard Dawkins. "The show's not really about attacking fundamentalism," says Ince. "It's mostly whizz-bang science, songs and people larking about. It's about celebrating life." To get us in the mood, Ince and Cox allowed the Guardian to quiz them about how it's possible to square a belief in rationalism with a desire to enjoy the season of goodwill.

Can you use a belief in rationalism as an excuse for not sending Christmas cards?

Robin I think going, "Oh, I'm so scatty because I was thinking about the universe" is a much better excuse. "I got distracted because I thought I saw the Higgs-Boson particle. It was Christmas and we were drinking, you know, ginger wine, and we chucked two glasses together at such speed that the particle appeared … so I just didn't get round to it."

Brian I don't want them, I don't send them. It's just good taste, it's not rationalism. Don't send the damn things. It's ridiculous.

Is it all right to enjoy Christmas carols?

Brian If you're asking me personally, I like them. It comes down to this question: can you build a society that's entirely rational? Can you give away all the emotional connections you've got, growing up in Britain, the excitement of Christmas, presents and carols and snow and all that? I like all that stuff. I don't think you should necessarily be aiming to live an entirely rational life. Rationalism's about embracing logic and a scientific worldview, but you can also embrace your culture and heritage and the things you enjoy. You can enjoy silly things.

Robin I love Christmas carols too, but if they ended a carol going "and now we're going to explain why all gays are going to hell", that's the cut-off point for me.

What would be behind the doors of a rationalist Advent calendar?

Brian You could have DNA.

Robin Yeah – 23 pairs of chromosomes, that's 23 windows. You'd have one extra one.

Brian Or Einstein's general theory of relativity. I'd have the great equations of physics.

Robin You could have an empty window; it's meant to have a neutrino in but you've just missed it.

Who should we celebrate, instead of Jesus?

Robin Richard Dawkins mentioned the idea of calling it Newtonmas, because Isaac Newton was also born – I say also, I mean Newton actually was – born on the 25th of December.

Brian The problem is that many of the people I could name, like Carl Sagan or Richard Feynman, they all shared this dislike of being on a pedestal. I'd completely remove the personification in terms of the celebration. Celebrate the ideas rather than the people.

Robin I was going to say we can celebrate the fact that, thanks to scientific advances, we got through our own births. And are still alive. We forget it's only 60 years ago that the graph on child mortality totally changed.

If three spirits appeared before you on Christmas eve, what would they have to show you to change your beliefs?

Robin Them just being there is enough. You look at them and go, "Yes, there they are, the talking dead." They don't have to say anything. And they go, "Oh, we will take you on a journey." No. It's fine. You've done it.

Brian It's my view that the existence of ghosts would contravene the second law of thermodynamics. The principle of the conservation of energy, and the fact that entropy always increases; you'd be hard put to throw that away. You'd have to rip the book up; that's what it would imply if you saw a ghost. I would say, "I could not be any more surprised than I am by the fact that thermodynamics appears to be shit."

How does Father Christmas manage to send all those presents?

Brian I think that just by travelling close to the speed of light he'd be fine.

Robin Does the many worlds interpretation in any way help? Is there any possibility if we look at Deepak Chopra's interpretation of the many worlds theory ...

Brian No.

Robin [Ignoring him] … The many worlds interpretation of Father Christmas would be that there is one Father Christmas who makes the decision on a present for every child in the world, but because he makes every permutation of that decision, what happens is that every child gets a present in all of these different worlds. What we don't know is how he collapses the many worlds, how he collapses the waveform so that every child ends up with a present in their stocking. We don't know how Father Christmas does that.

As rationalists, should one also reject the Queen's Christmas message

Robin It definitely exists.

Brian I like it.

Robin Do you? That's only 'cos you think she might mention you. You think you might be in it.

Brian I liked growing up with Christmas. I liked watching Morecambe & Wise, I liked the Queen's speech because it was on and everyone listened to it. It's a specifically 70s Christmas that I like. I like Christmas Top Of The Pops with Shakin' Stevens on it [Stick to the facts. He didn't appear on it till 1981 – Ed]

Shouldn't we be calling Christmas 'winterval'?

Brian The point about scepticism or rationalism or whatever you want to call it is that it's a very relaxed view of the world. Why would you get offended about calling something Christmas? It's nothing to do with anything. It's got nothing to do with a scientific worldview. Christmas is fine.

Robin What about XXmas, or XYmas, in which we celebrate the dawn of genetics? I like the idea of XXmas, where we celebrate Crick and Watson.

Are there any rationalist jokes that would be suitable for a Christmas cracker?

Robin My favourite science joke? There's a car speeding down the road with Heisenberg in it. And the policeman pulls him over and says, "Do you know how fast you were going?" And he says, "No, but I know exactly where I am."

Who would be your nightmare Christmas guest?

Robin There's such a list …

Brian Deepak Chopra. Although I quite like controversial people. I like people I can argue with.

Robin Yeah, you like fighting with people and going, "Look at those idiots", don't you?

Brian I do. I like being angry. So people who make me angry would be my ideal guests.

What would happen if it really were Christmas every day?

Brian I think we'd be totally fucked. No shops would be open. So we'd very quickly starve. Having said that, the curry house near me in Oldham is open on Christmas Day.

Robin What you're really saying is that it'd have a lot of ramifications for Oldham. It'd be like Cormac McCarthy's The Road, but in Oldham. People would be walking along going, "There's this place called Oldham, and we can eat there. We're going to make it!"

Uncaged Monkeys is at the Plymouth Pavilions, 10 Dec, HMV Apollo, W6, 13 & 14 Dec, and Brighton Concert Hall, 15 Dec. Nine Lessons And Carols For Godless People is at Bloomsbury Theatre, WC2, 18-23 Dec