Let's Disassemble Mercury

How a lifeless rock could hold a trillion humans.

It’s hard for people to grasp how big humanity can become.

My favorite way to explain this is to talk about disassembling Mercury. Yes, taking the whole thing apart.

Mercury is the smallest planet, it is about 1/3 the size of Earth.

It is literally a rock, floating around the sun. No life. There are probably some Mercury enthusiasts, but it can’t be many.

So let’s take it apart. I mean, when we talk about taking it apart, we will create Mercury preservationists, campaigning to keep the pristine rock beauty intact for nobody to see.

It’s a rock that has a mass of about 3.285 × 10^23 kg, or about 300 billion gigatons. That is a lot of stuff! We could live on top of the rock, but that is pretty inefficient. If you gave me a giant pile of lumber, my first instinct wouldn’t be to make a wooden mountain and live on it. What if we make it into rotating space stations instead?

There is a type of space station called an “O’Neil Cylinder”, which is basically a large rotating tube. These stations are designed to be about 8km in diameter, and up to 32km long, so about 900sq km. This area is a bit smaller than the US state of Rhode Island and about the size of Los Angeles. So living in one would be…pretty normal for most people? Most people I know in LA don’t leave that often, it’s not a major restriction. Rotating the habitat generates centripetal force as a form of artificial gravity. This way, when you stand on the inside of it, it feels like Earth gravity…or mars or the moon, whatever you like. Lower gravity seems like it could plausibly create less stress on the body, and it’s one way to lose weight. So I suspect something like 80% of Earth’s gravity is optimal for humans, but who knows, we haven’t tried.

Image from Blue Origin

The best estimates for the mass of these things are 4-6 gigatons, mostly made of dirt, metal, and water.

But let’s assume that’s wrong, and it’s actually about 10 gigatons. Let’s also assume, and only about 1/3 of Mercury is usable then we can make about 10 billion stations.

This creates a living space of about 9 trillion sq kilometers. Earth is only 317 million square kilometers. This means we can make the landmass of over 28,000 earths, just out of Mercury, using very conservative assumptions.

If each of these calendars had 1/3 the population of Los Angeles, then you could fit 10 Quadrillion people in them. For most people, a “much more spread out Los Angeles” doesn’t sound like hell, but hey we don’t need to go for 10 Quadrillion people. We could go for like 1 Quadrillion people? I picked the subheader of the blog targeting 1 trillion people because I thought that was the largest number that people could sort of understand. At 1 trillion people, everyone basically has their own city’s worth of space. So this is far from hell, this is paradise.

It’s also rare to have visions of the future where you can be off by a factor of like 10,000 and still be right.

How we do it

Given that we CAN easily get a trillion people in space, HOW do we actually do it?

There are not really big unknowns from a physics perspective. There are 2 main things that we do need to start figuring out, and these will take a while:

1. How does the human body withstand long periods under artificial gravity?

2. How do we actually build something this big?

I’m not too worried about each of them, but I think getting a great start would be trying to build a rotating space habitat that is large enough to run tests, maybe 1-4 years long, to see how people do. SpaceX’s starship makes this kind of thing much more viable. Each of them is significantly bigger than the ISS. Tie two of them together and give them a spin, and you have a good experiment of the medical effects. ISS astronauts live in much smaller spaces for a year, and some people don’t leave their neighborhoods for a year. So this doesn’t seem that hard to test.

I’m interested to see tests on low-G (like the moon or Mars gravity). Based on what tests we have seen in zero gravity, there are negative health effects of zero-G. But it isn’t THAT bad. When we first sent astronauts up, we didn’t know if they would all die after 1 year in zero-G. So that’s a win! It’s pretty reasonable to think that zero-G is bad (our bodies were designed for gravity) but again low-G is maybe good?

Building something this large also doesn’t seem “that hard”, it’s just a matter of scale and time. If I asked a warehouse building company to build a warehouse 10x the size of the largest one, they could do it. It’s a lot of engineering and work, but it is something that can be done. Each individual O’Neil calendar seems easier than the Large Hadron Collider, for example. It doesn’t have to have the really hard things that are here on earth like “dealing with politicians” and “coordinating between countries” and “finding suppliers in good districts.”

We have a lot of work to do before actually trying to disassemble Mercury. And maybe it won’t work. But you probably haven’t thought about disassembling Mercury before, and it is my favorite example of how big we can make humanity without even leaving our cosmic backyard.