Why is 42 "the answer to the universe"?

Chris put this question to maths communicator James Grime from Numberphile...

James - 42 is a significant number because it was used by Douglas Adams as the answer to life, the universe, and everything, in a  Hitchhiker’s Guide. Now, I can give you Douglas Adams’s answer first which is, it was a joke. And he had to pick a number and it had to be small to be funny. It had to be small. It had to be not significant. So you can't have a round number. That’s not funny and 42 will do. And I think it’s the sound as well. It has a sort of ‘ooh’ sounds, forty-two in English. So, it’s a funny number. It’s been used before as a funny number. Monty Python have used it. Lewis Carroll also used it in the same sort of way. I know someone who used to go through the phone book and find ways of making them phone numbers into 42.

Beverley - He or she? Were they a mathematician?

James - I don’t think they were. I don’t think they were. I think if you do something like that, the number 42 should really appear one out a hundred times. So, each – all things being equal, each two-digit number should be appearing, one in a hundred times. Though I have interesting things about 42. If you fold a piece of paper 42 times, it will reach from here to the moon.

Chris - I don’t think you could fold a piece of paper 42 times.

James - Yeah, I don’t think. So if you double it. Just imagine doubling a piece of paper. The width would reach from here to the moon. Someone who suggested that an efficient way of traveling around the world would be to take your two points on the globe, to drill a hole from one point to the other, have a nice frictionless tube going through the earth, and it would take 42 minutes just by force of gravity alone, just to drift from one point, and it will always take 42 minutes no matter where you're traveling to.

Chris - The only problem with that is of course that the pressure that the air would be under in that tube. Because obviously, as you descend further towards the centre of mass of earth, gravity means that you're making the gas more and more dense. The density of the gas in the middle of that tube, I think I'm right on that, aren’t I Jess, it would be something like running into a brick wall.

Jess - Yeah.

Chris - So, it wold probably take you a lot longer than your 42 minutes.

James - It’s clearly not 42.

Chris - Beverley?

Beverley - There's another answer. I've seen various calculations on how many kingdoms of life there are. It’s very hard to decide how many kingdoms. Everyone is taught five at school – plants animals, fungi, and so on. But most of the kingdoms of life out there are microbial. They all look the same to us. They differ in their chemistry. And so with the analysis of how many kingdoms there are in biology come up with 42, as an answer.

James - I am not surprised. I think it’s an example of a kind of confirmation bias. If you go looking for it, you will find it.

Chris - So, we blame Monty Python and Douglas Adams, but beyond that, it’s just because it sounds nice to say.

James - I would think so.

Chris - Did the Chinese people who speak quite differently, did they like the number as well or do they have their own magic ‘nice to say’ number?

James - So, I know that the science communicator, Alex Bellos has looked at world’s favourite numbers and there are cultural variations around the world. In the western world, you’ve asked for a favourite number, you'll get the number 7. But in China, you'll get the number 4, I believe.

Beverley - Is it about the number of syllables in the number? I've heard that Chinese people are much more mathematically-minded because there are far fewer syllables in their numbers especially – so going from 1 to 10, they can learn those much, much quicker than we can?

James - I can't speak to that. I know they have different systems of learning things though..