Project Hail Mary

by Andy Weir

That was the answer to the long-asked question: Why is Astrophage’s critical temperature what it is? Why not hotter? Why not colder? Astrophage makes neutrinos in pairs by slamming protons together. For the reaction to work, the protons need to collide with a higher kinetic energy than the mass energy of two neutrinos. If you work backward from the mass of a neutrino, you know the velocity those protons have to collide at. And when you know the velocity of particles in an object, you know its temperature. To have enough kinetic energy to make neutrinos, the protons have to be 96.415 degrees Celsius. “Oh man,” I said. “So any heat energy above the critical temperature will just make the protons collide harder.” “Yes. They’ll make neutrinos and have leftover energy.