The Canadian astronaut Chris Hadfield spent five months in 2012 and 2013 twirling around the Earth in command of the International Space Station. Hadfield guesses he made several thousand orbits of the planet during that time, and though he was never exactly bored, he certainly found some novel hobbies – tweeting astonishing pictures (he took 45,000) and at one point posting a video cover version of David Bowie’s Space Oddity that went viral back on Earth. Arguably the first astronaut to properly intrigue the masses since the 1960s, Hadfield, 56, has published two books since he landed. His Major Tom has been viewed more than 27m times.

The American artist Randall Munroe knows something, too, about capturing an audience in the age of the fast and fickle online share. Munroe’s webcomics, produced under the banner of xkcd and promising “romance, sarcasm, math and language”, have for years been a part of the social media fabric.

Formerly a Nasa physicist, the 31-year-old has a deceptively lo-fi style, his stick drawings and wobbly-lined infographics tackling complex issues. He can be tart, and the work is funniest when exploring what happens when science and technology clash with reactionary thinking. He is a longstanding admirer of Hadfield, and asked Weekend to get in touch with the astronaut. When a conversation between them took place earlier this month, Munroe was happy to discover that Hadfield read and liked his cartoons. Quickly they began to discuss space movies, Munroe curious, in particular, about the 2013 film Gravity…

Randall Munroe I spent the whole of that movie trying to recognise the Earth’s terrain in the background of scenes. I’ve always been a geography enthusiast and I kept wanting to identify where they were in their orbit. I’m curious whether, when you looked out the window on the International Space Station, did you always know where you were from a glance? What’s the longest you have to go thinking, “Well, that looks like Jamaica…”?

Chris Hadfield North is never up, which is disorienting when you grew up with maps. You have to break that bias, and be able to recognise Madagascar upside down. If you ever see a coastline, you can immediately work out where you are. And you’re often in sight of some island; the Canaries might help you. The Sahara is obvious – it’s the Sahara. You always know the Outback, the Mongolian desert. Europe is harder, the borders are hazy – you’re looking for the big rivers, mountain ranges. After a while, after a thousand times around the Earth, you get to know the world pretty well. It becomes intuitive, and you can just glance: “Oh, there’s Vesuvius.”

RM That’s so cool!

CH Of course, 70% of the time you’re over water. But actually, after a while, you can work out what part of the world’s water you’re over, because of the cloud patterns. You know what the north Pacific looks like, what the south Atlantic looks like; they’re instantly recognisable. You feel like you’re over the Pacific forever, even [in a space station] moving at five miles a second. You know, I’ve been asked astronaut questions for 23 years, Randall, and nobody has ever asked me this. It bodes well.

RM I feel like, when you have an astronaut and a cartoonist talking, only one of those people is professionally required to be good at doing things under pressure. That takes the onus off me here. Did you ever watch Gravity? If so, did you find the background as distracting as I did?

CH About halfway through the movie I stopped worrying. There were so many lapses of fact – similar but not right.

RM There was one point when they passed over what looked like central Scandinavia. Which would have been too far north [for their orbit], right?

CH It looked very much to me that, for a whole bunch of the movie, the Earth was turning the wrong way.

RM A lot of the time, when I find myself critiquing scientific accuracy in movies, I have to remind myself that it had to get close enough to getting it right to get things wrong. It’s rare that you get a movie that makes people want to talk to real astronauts and ask them about it, you know? If a movie isn’t trying to get the physics right at all, no one bothers to ask physicists about it. So I try to rein in my instinct to say, “This is wrong, this is wrong, this is wrong.”

Facebook Twitter Pinterest Chris Hadfield: ‘I’ve been asked astronaut questions

for 23 years, Randall, and nobody has ever asked me this.’ Photograph: David Levene/The Guardian

CH When the original moon landings happened, Nasa and the United States decided to make it part of pop culture. They directly transmitted whatever happened, during Neil and Buzz’s descent – the original reality television! They took a huge chance and said, “We think this is too important to keep to ourselves, we’re going to let everyone see it.” It had an enormous impact on millions of people – because they put something factual and cultural out there, something right on the edge of reality, not just a scientific fact but a human event. By the way, Randall, I stole something from one of your cartoons. I used it just today in conversation.

RM Which one?

CH The one about how fast a space station flies across New York.

RM I thought to myself, I can write down five miles a second, or whatever it is. But I didn’t know what that meant. I know I can only run at 15 miles an hour; what does five miles a second mean in a way I can picture? And one of the devices I came up with to explain it was, if you were listening to music while moving at that speed through New York, every beat of the song you’d be at this landmark, this landmark, this landmark.

CH You chose the song 500 Miles by the Proclaimers. I liked that.

RM There’s a common piece of advice you’re given, if you’re going to speak in public: open with a joke. Because it does so much. It tells the audience, right away, that the speaker looks at the world in a fun, normal-person way. Some of the first infographics I did started off as notes to myself: trying to plot out, for instance, how IP addresses are allocated. After a while I thought, “This is a neat thing I can share with people, and they can follow me along in that process of understanding.”

CH The news that just came back from Pluto today was interesting. They discovered these ice volcanoes, but when you looked at the actual data it was really complex. So they took the topographic pictures and they coloured them for altitude: brown for high, blue for medium, green for low. And suddenly, just by simplifying through colour, you could intuitively understand something complex. It was presented in a culturally friendly way, and I think if you’re trying to explain something complex – whether by teaching them a rhyme, or drawing a stick figure – it keeps people engaged.

A joke does so much. It says that you look at the world in a fun, normal-person way

RM When you’re orbiting, do you go far enough north to spot the crater in central Quebec? It’s one of my favourite geological features on satellite photographs.

CH Oh, Lac Manicouagan? We went right smack down over Lac Manicouagan! I used to be a fighter pilot and I flew F18s down inside Manicouagan. So it was beautiful to see it from space. It’s an asteroid crater they flooded as part of a hydroelectric project. That crater’s a couple of hundred million years old.

RM Yeah! I was really surprised to learn it was that old. I would have assumed it couldn’t be that old because the cycles of glaciation would have wiped it out, but I guess it’s just so big.

CH So big. We think the Earth was hit by a few [such asteroids] at the same time. It’s something that really seeps into you, orbiting up there – you get a sense of the age of the world. Everyone gets so concerned about their particular 80 years on Earth, as if somehow the entire universe was a gigantic pyramid assembling to this little point, right now, which is my lifespan – the only worthwhile end product of 13.5bn years of existence. What started seeping into me on, I don’t know, my second-thousandth time around the world, seeing all the ancient scars, was the incredible temporal patience of the world.

RM I’ve read a couple of books by geologists, making the argument that one of the most important things to come out of Earth science in general is the concept of deep time. The concept of things being that old.

Facebook Twitter Pinterest Randall Monroe: ‘When you looked down at Earth, did you always know where you were?’ Photograph: Josh Andrus/The Guardian

CH We talk about UFOs, about discovering life on other planets. But nobody intuitively understands what a billion means. If you talk to the average person and say, “What’s the difference between three billion and four billion?” your gut answer is, “One.” When we start talking about the Earth being four and a half billion years old, and the universe being around for nine billion years before the Earth was even formed – how do you start to put that into the context of the search for other forms of life? For the unfathomably huge distances we’d be talking?

RM It’s not just that we’ve been bad about educating people about numbers. This is a hard idea! There’s an inherent difficulty in connecting it all up. Maybe it takes going into space, flying around and staring at the world, before you can begin.

CH We are potentially right on the cusp of discovering if we’re alone in the universe or not. The discoveries we’ve made in the last couple of years, of other places where liquid water exists – on Mars, on [Jupiter’s moon] Europa, on [Saturn’s moon] Enceladus – where there’s enough heat to keep the water liquid. Anywhere on Earth you have heat and water, you have life. So we may [soon] be able to see if we’re alone in the universe or not. That’s exciting to me.

RM And on top of the exploration of our own solar system, the explosion in [the discovery of] exoplanets has just thrilled me. Even if we’re a little way away from some of the really good answers, it’s like, no matter what we do, we’re going to be making cool discoveries with it. What else excites you about the future?

We are right on the cusp of discovering if we’re alone in the universe or not

CH Our ability to communicate thought – the democratisation of thought. The printing press sort of started it. The telephone took it to the next level. But the internet? Social media? It expands it to a level that’s unprecedented. There’s a chance now, especially with the level of literacy that we’ve achieved in the last 25 years, and the decrease in infant mortality – we’re at the point now where we are not wasting very much human potential. The brightest minds in the world are at the point, now, where almost all of them can access the sum knowledge of the world. That’s pretty exciting, the self-accelerating nature of giving knowledge to people who have the ability to crack it and turn it into new inventions and ideas.

RM Yeah. I’m always a little wary of assuming that technology is going to make things better, though.

CH Right.

RM I feel like a lot of people who are in my world look at climate change, for example, and say, “This is just a technical problem. We need to solve it.” When I think, at the moment, it’s a political problem first and foremost. People in my world can be disdainful of political and social problems and solutions. But we’re never going to stop needing those.

CH I think part of what motivates me and, I think, you, is that if you want to have an effective discussion of technical issues they have to be fact-based. And how do you get voters and politicians to make the issues fact-based? If the only way that you present [arguments] is to other nerd royalty, then you’re not going to make a convincing case. What’s important to me about the way you express complex ideas in your cartoons is that it allows people access to a complex idea, and maybe helps them make an informed decision. For me, it’s like: “I think my thinking on this issue is clear.” And then I look at some of your descriptions and I realise I only had a bunch of nebulous thoughts. I love it when someone else has taken a thought deeper than I have.

RM But if you read all of my hundreds of incoherent thoughts leading up to the final cartoon… I get to just draw the last thought, and that makes it easy.

CH I sometimes think that the brain is normally like this flat little Jiffy bag. But if you can put it over the right heat source, suddenly it pops to a size you hadn’t anticipated. If you’re trying to explain to someone how fast five miles a second is, that’s hard. But offer them a visualisation of a space station flying over New York and suddenly it means something.

RM It’s like reading a fantasy novel where you don’t realise there’s a map in the front of the book. You get to the end of the story and then notice the map – and suddenly all of the things that happened fit together.

CH I hope we chat again, Randall. Wherever there’s good conversation, I always wish there was more time.

RM We’ll speak again.

CH I imagine we will. It’s a small world!

RM Small. But very old.

• Introduction by Tom Lamont. This conversation has been edited for length. Thing Explainer: Complicated Stuff In Simple Words by Randall Munroe is published by John Murray this week, at £16.99. To order a copy for £12.99, go to bookshop.theguardian.com or call 0330 333 6846.