8 October 2021

Project Hail Mary – Andy Weir

Of all the things I teach my students, numerical bases are the hardest to make them truly understand. There’s nothing special about the number 10. We have ten unique digits because we have ten fingers. Simple as that.

During the conversation, I learned the Blip-A has no radiation protection at all. And I know why Eridians never discovered radiation. It took a while to assemble all of this information, but here is what I know: Erid is extremely close to its star—about one-fifth as far as Earth is from our sun. Their “year” is a little over forty-two Earth days long. It’s what we call a “super-Earth,” weighing in at eight and a half times Earth’s mass. It’s about twice Earth’s diameter, and a little over double the surface gravity. Also, it spins very fast. Absurdly fast. Their day is only 5.1 hours long. That’s when things started to fall into place. Planets get magnetic fields if the conditions are right. You have to have a molten-iron core, you have to be in the magnetic field of a star, and you have to be spinning. If all three of these things are true, you get a magnetic field. Earth has one—that’s why compasses work. Erid has all of those features on steroids. They are larger than Earth, with a larger iron core. They are close to their star, so they have a much stronger magnetic field powering their own field, and they spin extremely fast. All told, Erid’s magnetic field is at least twenty-five times as strong as Earth’s. Plus, their atmosphere is extremely thick. Twenty-nine times as thick. You know what strong magnetic fields and thick atmospheres are really good at? Radiation protection. All life on Earth evolved to deal with radiation. Our DNA has error-correction built in because we’re constantly bombarded with radiation from the sun and from space in general. Our magnetic field and atmosphere protect us somewhat, but not 100 percent. For Erid, it’s 100 percent. Radiation just doesn’t get to the ground. Light doesn’t even get to the ground – that’s why they never evolved eyes. The surface is pitch-dark. How does a biosphere exist in total darkness? I haven’t asked Rocky how that works yet, but there is plenty of life deep in Earth’s oceans where the sun doesn’t shine. So it’s definitely doable. Eridians are extremely susceptible to radiation, and they never even knew it existed.

Gravity doesn’t just “go away” when you’re in orbit. In fact, the gravity you experience in orbit is pretty much the same as you’d experience on the ground. The weightlessness that astronauts experience while in orbit comes from constantly falling. But the curvature of the Earth makes the ground go away at the same rate you fall. So you just fall forever.

With the newly free hand, he scrapes his workbench. “You hear this, question?” “Yes.” “That is sound of predator approaching you. That is sound of prey running away. Sound of object touching object very important. Evolve to hear.” “Ah! Yes.” It’s obvious now that he points it out. Voices, instruments, birdcalls, whatever—they can all be wildly different sounds. But the sound of objects colliding isn’t going to have much variance from planet to planet. If I bang two rocks together on Earth, they’re going to make the same noise as if I bang them together on Erid. So we’re all selected-for by being able to hear it.

You’re a coward and you always have been. You abandoned a promising scientific career because people didn’t like a paper you wrote. You retreated to the safety of children who worship you for being the cool teacher. You don’t have a romantic partner in your life because that would mean you might suffer heartbreak. You avoid risk like the plague.

We tend to think of solid materials as magical barriers. But at the molecular scale they’re not. They’re strands of molecules or lattices of atoms or both. When you get down to the teeny, tiny realm, solid objects are more like thick jungles than brick walls. I can work my way through a jungle, no problem. I may have to climb over bushes, weave around trees, and duck under branches, but I can make it. Imagine a thousand tennis-ball launchers at the edge of that jungle aimed in random directions. How deep into the jungle will the tennis balls get? Most of them won’t get past the first few trees. Some may get lucky bounces and go a little deeper in. Fewer still may get multiple lucky bounces. But pretty soon, even the luckiest tennis ball runs out of energy. You’d be hard-pressed to find any tennis balls 50 feet into that jungle. Now, let’s say it’s a mile wide. I can make it to the other side, but there’s just no chance a tennis ball can. That’s the difference between Taumoeba and nitrogen. The nitrogen is just moving in a line and bouncing off stuff like a tennis ball. It’s inert. But Taumoeba is like me. It has stimulus-response capabilities. It senses its environment and takes directed action based on that sensory input. We already know it can find Astrophage and move toward it. It definitely has senses. But nitrogen atoms are ruled by entropy. They won’t “exert effort” to do anything. I can walk uphill. But a tennis ball can only roll so far before it rolls back down.