278THE WORLD AT THE END OF TIME Frederik Pohi 279
Human astrophysicists would have envied him that first-hand knowledge. For a human
astronomer to make a model of what the inside of a star was like was an exercise in observation,
deduction, and just plain guessing. Humans could never see inside a star. The longer the humans
worked at it, the better their guesses on the subject got—but Wan-To didn’t have to guess. He
knew.
That isn’t all an Earth person might have envied Wan-To for. Really, he had a pretty
joyous life—at least, when he wasn’t terrified. For Wan-To, living in a star was fun. In any star
he happened to occupy he could always find a satisfying variety of environments. He could even
find a wide choice of “climates,” and he had all sorts of vastly differing particles to amuse
himself with, though some elements were a lot scarcer than others. For instance, if you took a
random sample of a million atoms out of Wan-To’s star, mixed well from all of its parts, only one
of those atoms would be the element argon. Two or three atoms each would be aluminum,
calcium, sodium, and nickel; sixteen would be sulfur; thirty or forty each would be silicon,
magnesium, neon, and iron. You’d probably find eighty or ninety atoms of nitrogen, 400-plus of
carbon, nearly 700 of oxygen. (If you took a larger sample—if you counted every atom in the
star—of course you’d find a lot of other elements. In fact, you’d find all the other elements, from
beryllium to the transuranics. Inevitably some freak of fusion would manufacture at least a few of
every atom that could possibly be made, somewhere inside Wan-To’s star. But all the elements
named—every element that ever existed, save two—would still amount to fewer than 2,000
atoms in your sample of a million.)
The rest of your million-atom sample would be just those two heavy hitters, though not at
all in equal proportions. You would find some 63,000 atoms of helium; and then the rest, 935,000
atoms out of the million, would be hydrogen. So you might think of Wan-To’s star as being a
very dry Martini indeed. Hydrogen was the gin, helium the dash of vermouth, and all the rest
were just contaminants leached off the olive, the stirring rod, and the glass it came in.
There were plenty of all these things in Wan-To’s dense central core to play with, and
anyway, if he tired of them he didn’t have to stay in the core. He had the whole star to play in,
and it was a million miles across, with a hundred different regimes. He could “wander” at will
from “room” to “room” of his “home”—spending some time in the outer shells, even the
photosphere; venturing (with care, because they were so thrillingly diffuse) into the corona and
the nearer parts of the solar wind; riding up and down in the upwellings of hot gases that made
sunspots and speculae.
That part of Wan-To’s star was the convection zone, and in some ways it was the best of
all. The convection zone was the layer of the star where simple mechanical transport took over
from radiation in the escape of energy from the star’s core. For the first four-fifths of its escape
from core to surface, a photon of energy traveled purely radiatively. Not exactly in a straight line,
of course; it bounced from particle to particle, like a ball in a pinball machine. But a fifth of the
way down from the surface the pressure was lessened enough so that the gases could move about
a bit—which is to say, convectively, and so it was called the convection zone. There the heat
from the core made its way the rest of the distance to the surface by being transported in cells of
hot gas, like the outwelling of warmth from a hot-air heating system. Some of the gas rose to the
surface and again began radiating, ejecting its heat away into space. Some, cooling, fell back. In
the convection zone Wan-To could cavort freely, letting himself be carried along by the
convection cells when he chose, twisting their paths into amusing tangles when that seemed more
interesting. Oh, there were a million places to play inside a star!
For that matter, there was no reason for him to be bored with the core. There was plenty
of variety even there. If he decided the center was a little too warm (it ran about fifteen million