"This is where that Possil meteorite fell, intit?" he says, as we're passing Lambhill Cemetery.
"Yeah over there, near the loch."
"What's so great about meteorites?" he says. "They're just lumps of stone."
"Or iron. But some are unchanged since the dawn of the solar system. They're the carbonaceous chondrites and they tell you loads about the sun and planets, as they coalesced from a cloud of interstellar gas."
"I thought god made them all," he says.
"In six days then took Sunday off," I say. "You're right. Hasn't got back to the job since, as far as I can see."
"Hopped a plane to Tenerife and is drinking beer and chatting up scantily-clad women as we speak," he says.
At the narrow bridge over the Kelvin, a bus crosses the centre line, forcing me to give way. "When I was at uni I shared a flat with a bunch of guys," I say, letting the clutch in and moving off again. "We used to sit around the kitchen, chatting and interacting."
"Like on Facebook?" he says.
"Yeah, except you could touch each other. Not that we wanted to. One of the flatmates had these stock phrases he used all the time. A favourite was 'bone-idle bastard'."
"Are you working round to saying god is a bone-idle bastard?" he says.
"You got a problem with that?"
"Could you wait till I'm out the car?" he says. "I don't want meteors raining down on my head. What did you want to ask me about art?"
"It's these horses' heads," I say.
"You been finding them in your bed, again?" he says.
"No, I mean the huge sculptures by Andy Scott out Falkirk way."
"The Kelpies?" he says.
"That's them," I say. "Spectacular. Kinda gorgeous. One of these London art critics has been writing that they're 'a pile of horse poo'."
"It's a fair point," he says. "They're corporate art. They are what they are. Criticising them for not being something else is obvious and pointless. But he's paid for writing, so that's what he does."
"But this guy's got no art qualifications," I say. "He's a journalist who says things like, 'bad reviews can be bloody good fun to read'. He gets his kicks by being destructive about creative people. Doesn't that bother you?"
"A little," he says. "What bothers me more is that there's a lot of ill-informed opinion about art. People say it's inaccessible - which it is if you don't care enough to access it. We've just had the Glasgow International with dozens of free exhibitions by first-class artists. How many of these people went to see them?"
"Forty-two," I tell him.
"I doubt it," he says. "They talk about how shit Tracey Emin and Yoko Ono are. They're not. They are good artists. They're also well known and well paid. For each one of them there are thousands of artists doing loads of interesting stuff. If you want to mouth off about art, learn something about it first."
"I will," I say.
"You science chaps have it easy," he says. "Nobody tells Higgs his boson is inaccessible, do they?
"No they don't," I say.
"Nobody goes 'Your carbonaceous chondrites are a pile of poo', do they?" he says.
"No they don't," I say.
"Art is a process, same as science," he says. "You look at a meteor and think about what happened in the early solar system. I see a lump of stone. I look at an art work and think about materials, methods and motivation. They see a pile of poo."
"Nice analogy," I say.
"What they should do, right?" he says. "What they should do, before they start pontificating about art, is make the effort to find out about it first.
"But will they?" he says.
"No, they won't," I say.
"Why not?" he says.
"Because they're bone-idle bastards," I say.
"Correct," he tells me.