My Conversation with Andy Weir

Andy was great, here is the text and audio, here is the introductory summary:

Before writing a single word of his new book Artemis, Andy Weir worked out the economics of a lunar colony. Without the economics, how could the story hew to the hard sci-fi style Weir cornered the market on with The Martian? And, more importantly, how else can Tyler find out much a Cantonese meal would run him on the moon?

In addition to these important questions of lunar economics, Andy and Tyler talk about the technophobic trend in science fiction, private space efforts, seasteading, cryptocurrencies, the value of a human life, the outdated Outer Space Treaty, stories based on rebellion vs. cooperation, Heinlein, Asimov, Weir’s favorite episode of Star Trek, and the formula for finding someone else when stranded on a lonely planet.

My favorite part was this, which Andy answered with no hesitation:

COWEN: What if there were two immortal people, let’s say it’s the two of us, placed on opposite sides of the Earth, an Earth-like planet, and we can wander freely with no constraints but just foot speed. How long does it take us to find each other?

WEIR: Can we collude in advance in any way?

COWEN: No, we cannot.


COWEN: But we know we’re trying to find each other.

WEIR: We know we’re trying to find each other. Well, we should both — but can we have a — are we both rational actors and we —

COWEN: We’re as rational as you and I are; take that as you wish.

WEIR: So, no?



WEIR: I think the best thing to do would be for both of us to pick an arbitrary great circle to walk, around the planet, and leave markings along the way denoting what direction you’re walking. So I would arbitrarily pick a direction to go and I would just go that direction with the intention of circumnavigating the entire globe, and I would walk at maybe half what is a comfortable speed for me. And you would do the same thing. Now, somewhere, our two — in fact, in two points — our great circles will intersect.

COWEN: Right.

WEIR: And when one of us reaches the other one’s, then they start following the markers at full speed, and then you get the guy. Right?

COWEN: And what’s your best guess as to how long that would take?

WEIR: Well, if you pick two points, I’m guessing one of us would have to walk probably about a quarter of the way around the planet before we found the other one’s great circle. And then you’d have to walk again. So in terms of circumnavigation times, it would take you 2x to get all the way around the planet, because my initial plan was you’d walk half-speed. So I’m guessing it would be a quarter of that, so one-half x to get to your great circle, and then a quarter x to find you along your great circle, on average, I’m guessing. So one-half plus a quarter, so .75x. So three-quarters of the time that it would take to circumnavigate the planet.

COWEN: OK, great answer.

WEIR: That’s my guess.

Do read/listen to the whole thing


Water is the big problem with that idea.

we will fashion cairns from kelp

Even as a stand-alone comment, this is hilarious. But I suspect it's a reference to something. Can you help?

It's an interesting Rorschach test of popular culture. It is a hilarious comment, but my supposition was that Jeff Holmes thought it up purely in response do dan1111's comment.

But one can imagine that the "cairns from kelp" image is indeed inspired by a scene or image from elsewhere: Finding Nemo, Waterworld, The Little Mermaid, 20,000 Leagues Under the Sea, etc.. I've only seen the Finding Nemo/Dory movies, and fragments of Waterworld and 20K Leagues, so maybe there is a scene or image from one of the other movies about oceanic trail-marking.

In Finding Dory, the parents left a trail of pebbles on the ocean floor to mark the way back home. If the two immortal beings are literally drown-proof, then water is not an obstacle and they can keep marking their trails underwater.

The kelp bit was thanks to this scene:

I suppose the idea of an improbable ocean hypothetical helped bring it to mind.

And I've always loved the word "cairn". Presto!

Ever been to the town of Cairns in Queensland, Aus?

I've not had the honor.

So Kenya was picked because it was on the equator, had an ocean to the East and has smart people with business friendly policies.

Brazil also is on the equator and has an ocean to the East...

Actually, it could be two. According to Brazilian writer Medeiros e Albuquerque, in the late 19th Century, Brazil was in talks to absorb Ecuador and Colombia.

Step 1. Go to San Diego because it has the nicest weather on the planet.

Step 2. Enjoy yourself and wait for the other dummy to stop messing around in parts of the planet with lousy weather.

Actually, "Mendes possess the fourth Better Weather on the Planet, according to UNESCO." If an otherwise unremarkable Brazilian city has the fourth best weather in the world, it is clear where the first three better weathers are. Actually, many foreigners, after visiting Brazil, leave their homes, jobs, families and narions behing and never leave Brazil.

If you both have compasses, surely the obvious Schelling point is the magnetic north pole. Should only take max(uniform(0,0.5),uniform(0,0.5)) = 0.33x on average.

I would probably circle the earth several times hoping that this was not the other person's plan before going there.

I would try the other pole next, crossing your great circle!

I would have found you, buddy. But maybe we are atypical.

In any case the flaw with these approaches is the terrain. In the one Andy Weir mentions it is not necessarily having land that circumnavigates the globe. in the magnetic north pole, you're assuming the planet has a magnetic north pole, that it's located in a habitable clime and that there's land under it.

A better approach is just to follow a river till it empties in the ocean (or major sea), create a marker that indicates the general direction of travel and a note that finding a major river will be followed by the same behavior. That being said, it's highly unlikely that two people walking on a planet on their own would ever find each other. Planets are big.

Agreed. I thought the Northern Pole, magnetic or geographic was an obvious choice. They're not far apart so it wouldn't matter which.

Alternative Schelling would be Continental Pole of solitude; the centre of the "land".

"The magnetic north pole."
Beat me to it.

Note: A very similar was asked and answered in "What If?: Serious Scientific Answers to Absurd Hypothetical Questions" (specifically, the "Two Immortals" question, which is available on the Google preview). See also,

Won't you both intersect each other's path and switch to it and then miss each other? The smarter thing to do might be to find where they intersect and then wait.

But then wouldn't you both find an intersection and wait (potentially)?

Once every day I would leave a written statement of my travel plans, a suggestion of what to do if you find my path, and also what date I was at that point.

Yes, good point. Addendum: don't bother to leave a trail at all, so the other guy will just keep walking. That way you don't have to do near as much work.

Or try to hunt and kill the other guy. Movie logic says you'll locate him/her within a short period of time. Then you can decide not to kill him.

Hmmm...the answer is they never find each other, because they both hide, fortify their location, and work on homemade weapons?

What are random walks like on a surface of a sphere? Its a sub-set of a 2D plane, right?

Yup. So when you intersect the others circle, you know which way to go.

How do you know you've intersected his circle? You can't draw a chalk line around a planet.

Not sure about lunar economics. No air, water, or plate tectonics which suggests no minerals to mine.

"No air, water, or plate tectonics which suggests no minerals to mine."

Air & water don't effect minerals at all. And plate tectonics don't directly effect them either. Volcanism brings heavy minerals to the surface, but that's not a direct result of plate tectonics.

Lunar mining will probably be less economical than asteroid mining. And ion thrusters (and possibly the EM Drive ?) will make slow travel back and forth to the asteroid belt economically affordable. I imagine that lunar mining will tend to be restricted to minerals that can be easily mined and used locally on the moon.

Sorry I didn't mean to imply air or water affect minerals just that they make expenses increase exponentially. Lack of plate tectonics is more than no volcanoes. It is how mineral deposits are formed.

I am curious as to the solution mr Weir imagines.

"Lack of plate tectonics is more than no volcanoes. It is how mineral deposits are formed."

+1, I didn't know that.

"minerals" and "mineral deposits" used interchangeably?
In the Golden Books of my youth (Herbert Zim) they were more careful.

What is the sound of two gas giants orbiting each other?

Sad the Weir didn't consider Cowen's questions because they subvert the premise of the book even though they are good questions.

First, I would assume they were in San Diego and go there. If they don't turn up, I would assume they did turn up. Nothing more is needed, is it?

Surely you would assume they were in New York / LA, and if they didn't turn up, they probably weren't important anyway.

It would be pretty hard to leave enough markers that somewhere who crossed your trail at any point along it would be likely to see one. Especially markers that can last long enough for the other person to find them. And making so many easily visible, durable markers would certainly greatly increase travel time.

For the rest of the interview: I found it bizarre that Andy Weir claimed there are currently no other writers of hard science fiction. Has he heard of Greg Egan--probably the greatest writer of hard science fiction of all time? What about Peter Watts?

Yeah, quantity of markets is a major issue.

So we start with one fantasy condition (immortality on Earth), but other questions are not answered (at least, not in the excerpt):

* Do we have to deal with the Earth's terrain as is?
* What about all the other (mortal) people on the Earth, and man-made structures?
* Can we traverse oceans? Nasty mountains and deserts?
* How important is speed of locating the other person versus being comfortable (i.e. hanging out in San Diego or whatever)?

So, I'll posit a few more specifics.
* There are no other people on earth
* The Earth's geography is as in real life (oceans, etc)
* Man made structures exist, but decay over time
* We can't use long range communications devices
* We must use boats for oceans - this is difficult, but not impossible
* Finding each other is a priority, but not TOO big a priority

OK, so, the circles with markers approach seems pretty weak too me (too many markers, too impermanent, and oceans, polar regions, and the like make it impractical)

My approach would be to travel the world in somewhat leisurely fashion, focusing on logical major points of interest - NYC, San Fran, Tokyo, Hong Kong, Jerusalem, Rome, London, Paris, etc, and leave instructions at the major landmarks within these cities. Yes, the landmarks would be decaying, but the better built ones should hold up a few centuries. The instructions would indicate my general plans, locations I'd plan to revisit at certain intervals (to meet the other person, or at least read whatever instructions THAT person had left). Focus would probably be cities and landmarks, but not all would have to be man-made.

Quantity of *markers* not markets...

Switching to the other persons Great Circle would be a problem if he also did the same.

If you can't coordinate your actions, then how would you know to walk a Great Circle? His solution is an equilibrium but there's no reason to believe that's how people will play.

The worst possible thing is for both players is to stay put, but one staying put with a huge signal is probably best.

If there was a tallest mountain peak, that would be the best coordination mechanism for staying put, and traveling along waterways would be the best coordination for meeting while moving.

"The worst possible thing is for both players is to stay put, but one staying put with a huge signal is probably best."

This idea connects with Tyler's fascination with the Fermi Paradox and with extra-solar objects flying through our solar system. How should two advanced civilizations find each other in the galaxy? Stay put and send probes.

Personally though I don't think the so-called Paradox is a paradox at all (there's probably intelligent life in the universe, maybe on billions of planets, but they're in other galaxies and thus too far away to ever communicate with each other). And Oumuamua is a very interesting object, but to estimate non-trivial probabilities that it's constructed rather than natural is I think ... over-enthusiastic.

I look forward to reading the interview though. Is Weir's latest book worth reading? I've only seen a couple of reviews, which were positive.

This was a nice interview. I can see why this is the perfect guy to do hard science fiction (in a technological and economic sense, at the same time!).

I am disappointed that social media was not more of a hook, but maybe that is someone else's book.

I am also an optimist, and would choose +400 years, but I think we have a real "human brains on networks" problem to resolve in the next 50.

We are in the Boaty McBoatface century, and have political outcomes to prove it.

Two modern humans dropped on opposite sides of the earth would not survive for more than a couple of weeks (unless those spots just happened to be among the most hospitable on the planet...and they stayed put).

They were immortal according to the problem definition, though.

Ah yes, missed that. In that case, I guess they don't need to eat, drink, sleep or breathe and can just walk across oceans leaving markers on the sea bed. In that case, the problem boils down to two people on opposite sides of a giant, earth-sized marble.

Great interview Tyler!

I love his mention of Tunnel in the Sky . That's my second favorite Heinlein novel. It also illustrates by comparison the problems with many post-apocalyptic stories like The Walking Dead. In Tunnel in the Sky the main problems are the environment and intra-group politics, not other groups. It's also an interesting exploration of what sort of personality traits make for a good leader and what sort of social norms support cooperation and survival in a hostile environment. Unlike the Walking Dead, the aggressively anti-social tend to get killed off quickly, because they can't survive in the environment without the support of a social group.

"I love his mention of Tunnel in the Sky "

+1, a great Robinson Crusoe story

"Unlike the Walking Dead, the aggressively anti-social tend to get killed off quickly, because they can’t survive in the environment without the support of a social group."

The Walking Dead lost me around the third season when they went Mad Max. The whole idea was kind of silly. They're fighting through a world of zombies and yet the survivors are fighting each other. Why? If 99% of the population is now zombies then that means there is a plentiful supply of almost any non-perishable commodity. There's almost no reason to fight over anything. If the local mayor was crazy, people would just leave.

Season 3 should have been about the rebuilding of society and then perhaps a reveal that the Zombie plaque was actually an attack by an outside group.

They’re fighting through a world of zombies and yet the survivors are fighting each other. Why?

Exactly. People like Neegan would be dead by now. How could he have any loyal followers? As soon as his back was turned there would be a knife in it.

Also worth noting that the teleportation in Tunnel in the Sky is very expensive. So the dystopian scenario you discussed is maybe not realistic. Probably only a limited number of people could afford to use it and the power needed to supply it could be controlled.

His answer about parallels to flying seems weak. It skirts the issue that society is maybe 10x or 100x more skittish about loss of life than the West was in 1920s or 30s. Even the early failures of the Apollo project would get things scrapped today. Soldiers flying for reconnaisance in WWI had relatively high crash rates even before they started shooting at each other.

Given a massive increase in risk aversion, how would the US or Europe tolerate tourism that resulted in crashes far worse than the recent Washington state train derailment -- at least at the beginning? Any such crashes would lead politicians to conclude that things were too dangerous to permit. So the barrier for minimum fatalities would be stricter and costs would increase exponentially.

This is a good question. I think there are three answers:

(1) General risk aversion has increased, however that doesn't mean there aren't risk tolerant (or even hungry) individuals. A world that seems to have no shortage of free climbers, free divers, spelunkers etc. probably won't have difficulty recruiting people for potentially lethal space adventures. Virgin Galactic had no problem getting sign ups and deposits for its proposed (and obviously somewhat risky) sub-orbital flights. Note also that Virgin Galactic is still moving forward despite a fatal accident.

(2) Engineering has improved enormously since the early 1900s. The pioneers of aviation were basically fumbling around in the dark. We have the benefit of enormous amounts of accumulated knowledge. Overall I'd say the comparison to the early 1900s isn't particularly valid. A better comparison is probably to the early days of jet aviation in the late 1940s/early 1950s. We know a great deal about how to build rockets, but haven't yet worked out how drive failure rates down to the point where the technology can move from risk tolerant applications into more general use.

(3) Our society actually seems to get over large scale failures better than we might think. For example, the Malaysia Airlines Flight 370 disaster, which involved the completely unexplained loss of a modern airliner with massive loss of life doesn't seem to have dented our appetite for air travel even a little.

a big speaks sometimes, u just don't know it, goes by you just like data/flak

is ok, lil' papinos, we r here 4u

mega minds r here 4u, working 4u, and things are getting better & better each and everyday, in everyway

the other choice is we just disappear, and i happen to think too much been too special 4that2happen

What happen to the conversation with Ross Douthat? I had been looking forward to that one.


I suppose I will have to learn to exercise the virtue of patience then.

nice ladies always around, otherwise, why?

If our walking speeds are similar, and I switch onto your great circle in the same direction as you are walking, I may never catch you (and you have probably gone ~ 1/4 way around before I found your circle). For that reason I prefer to walk in the direction opposite you.

What a dumb answer. I would use my immortality to become the local crime boss, then a regional lord. I'd keep expanding my empire, and word would get around that Mark The Immortal was ruler of my vast kingdom. The other immortal would find me. Now, if we both pursued that strategy on opposite sides of the world, it might be a problem. But if I knew there was another immortal, I'd use a significant share of national GDP to set up an intelligence agency to look for the other one.

And when you find the other Immortal you have to behead him, because in the end there can be only one. So says Highlander:

Unless it's a she. Maybe we could get together and produce a race of immortals. Worth trying.

For anyone interested, the field of search games is devoted to solving problems of this type, many of which are easy to state but have proven very difficult to solve. Some context to the problem of rendesvous on a sphere is provided here by Steve Alpern:

One of Vernor Vinge’s brilliant stories - Marooned in Real-time - has a character alone on earth many millions of years in the future. Not only does she start walking but - if memory serves - she manipulates local apes into a state of hyper evolution.

Was Artemis written for Teens? I read it but wouldn’t recommend it to anyone over 16z

Surely if each person starts at opposite poles and immediately begins a great circle, their great circles would only intersect at the poles? Each person would need to walk an arbitrary distance, then make a turn to begin a different great circle with intersections at more likely points. 3/4 of a circumnavigation seems incredibly optimistic as it's just as likely that the intersection will occur on the "far" side of the planet with a subsequent possibility of an equally lengthy catch-up process.

As an economist is Tyler choosing to minimize for time or effort? If minimizing effort, then walking should be limited to finding a way to meet at a starting pole. If one person decided not to walk, then other person would only have to walk 1/2 the circumference... assuming they knew which one was doing the walking. If neither walked, then after an appropriate amount of time one or both would walk to the other pole. The question then is what to do if they both walked and what instruction to leave so that the choice of who makes the return is unambiguous. The minimum walk for both parties in this case is 0.5 the circumference and a max of 1.5.

It's an interesting logic puzzle of what instructions to leave so that both parties know which person should make the return trip. Would it need to be based on a physical phenomenon that both could see at the same time and thus make the same decision? But the instructions must allow for choice at that time - if each left (say) instructions that they would walk back if the moon (assuming there is one) is full or waning and the other returns if it is new or waxing at a specific time then there is no way to resolve the conflict.

Andy Weir pretends he knows lots of things. "Nation states solidified by 600 a.d. in western Europe"... um. No.

What sophomoric and pretentious poseur. Weak answers and weaker arguments almost for every question. Nothing worse than a guy who things he knows about everything. And to think he has tons of people hooked up...

If you want to read a story about colonizing the moon you are far better off with Ian McDonald's series. He certainly is a far smarter guy.

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