Rocky Moves In

A dodecahedron is a Platonic solid with 12 pentagonal faces. Rocky has pentagonal symmetry, so pentagonal faces make sense for his anatomy. Geometrically, it's nearly spherical (good for pressure containment) but buildable with flat panels.

Astrophages at 96.415°C absorb any heat above that temperature, acting as perfect coolant. For Rocky (who lives at 210°C), the astrophage absorbs excess ambient heat. The ball stays at ~96°C: cold for Rocky, but bearable inside insulating xenonite.

Without gravity or wheels, Rocky moves with powerful magnets adhering to iron guides in the tunnel. Magnets allow directional control from inside the ball without external contact.

Kleiber's rule suggests larger organisms tend to live longer. Eridians weigh 168 kg and have partially inorganic metabolism (metal bones, mercury blood), which could reduce biological wear.

A civilization where individuals live 700 years accumulates knowledge extraordinarily. An Eridian scientist can spend a century mastering their field before contributing. This might explain advances like xenonite.

Rocky has been at Tau Ceti for 46 years alone. For a being with 689-year life expectancy, 46 years is like 5-6 years for a human: a long time, but not a lifetime.

Grace brings: broad scientific knowledge (molecular biology, physics, chemistry), computers with analysis software, human lab instruments, the external collection unit Rocky needed.

Rocky brings: xenonite (strongest known material), extraordinary fabrication capability (can build anything with five prehensile hands), intimate knowledge of the Blip-A and Eridian biology.

Rocky tried for 46 years to solve the Tau Ceti problem without the right instrument. A single external sampling instrument marks the difference between success and failure. The right tools are as important as knowledge.

Some animals on Earth come close. The Greenland shark, dated by radiocarbon in the lenses of its eyes, lives at least 270 years and perhaps more than 400. The bowhead whale passes 200, and one ocean quahog clam reached 507 years, counted from the growth rings on its shell.

They all have something in common: they live in cold water and have very slow metabolisms. The chemistry of life speeds up with heat. As a rule of thumb, every extra 10°C makes reactions 2 to 3 times faster. A shark at 2°C "lives more slowly" than a mammal at 37°C, and its body wears out more slowly.

That's the Eridian paradox. Eridians live at about 210°C, 170 degrees hotter than us. With Earth chemistry, that would push their metabolism absurdly high and shorten their lives rather than lengthen them. For them to live 689 years, their biochemistry has to rest on reactions and materials very different from ours, far more stable at high temperature.

The novel hints at this with details like mercury blood and a mineral shell, but never explains it. It's a fair bit of licence: we don't know of any chemistry of life at those temperatures, so we can't say it's impossible, only that it would have to be very unlike our own.

Kleiber's rule says a mammal's basal metabolism is roughly B ≈ 70 × M^0.75 kilocalories a day, with M in kilograms. For a 70 kg person that's 70 × 24.2 ≈ 1,700 kcal/day, about 82 watts: the power of an old light bulb, which is what your body burns at rest.

Applied to Rocky (168 kg): 168^0.75 ≈ 46.7, so B ≈ 70 × 46.7 ≈ 3,270 kcal/day, about 158 watts. It's only a reference point, since the rule was worked out from Earth mammals, but it gives an order of magnitude for the heat Rocky produces.

Lifespan also scales with mass, more gently: roughly as M^0.25. If a 70 kg human lives about 80 years, a 168 kg one would live 80 × (168/70)^0.25 ≈ 80 × 1.24 ≈ 100 years. The Eridian 689 years is about 7 times what the rule predicts, so size alone doesn't explain Rocky's long life.

Now a fun calculation about Rocky's ball. If astrophage soaked up all his metabolic heat and stored it as mass (E = mc²), in a day it would take in 158 W × 86,400 s ≈ 1.4 × 10⁷ joules. Divided by c² (9 × 10¹⁶), that's about 0.15 micrograms of mass per day. As a coolant, astrophage is absurdly effective: a pinch would last for years.