Dave frowned as he tried to answer. "Well, I suppose the atmosphere is
oxygen and nitrogen, mostly; then there's the ionosphere and the ozone
layer. As I remember, the color of the sky is due to the scattering of
light--light rays being diffracted in the air."

"Beyond the air," Ser Perth said impatiently. "The sky itself!"

"Oh--space. We were just getting out there with manned ships. Mostly
vacuum, of course. Of course, we're still in the solar atmosphere, even
there, with the Van Allen belts and such things. Then there are the
stars, like our sun, but much more distant. The planets and the moon--"

"Ignorance was bad enough," Ser Perth interrupted in amazement. He
stared at Dave, shaking his head in disgust. "You obviously come from a
culture of even more superstition than ignorance. Dave Hanson, the sky
is no such thing. Put aside the myths you heard as a child. The sky is a
solid sphere that surrounds Earth. The stars are no more like the sun
than the glow of my cigarette is like a forest fire. They are lights on
the inside of the sphere, moving in patterns of the Star Art, nearer to
us than the hot lands to the south."

"Fort," Dave said. "Charles Fort said that in a book."

Ser Perth shrugged. "Then why make me say it again? This Fort was right.
At least one intelligent man lived in your world, I'm pleased to know.
The sky is a dome holding the sun, the stars and the wandering planets.
The problem is that the dome is cracking like a great, smashed
eggshell."

"What's beyond the dome?"