ombardment impinges up is ... is altered.
Profoundly and obscuredly altered, so that the atmosphere emitted from
the crater is quite definitely no longer air as we know it. It may be
corrosive, it may be poisonous in one or another of a hundred fashions,
it may be merely new and different; but it is no longer the air which we
human beings are used to breathing. And it is this fact, rather than the
destruction of the planet itself, which would end the possibility of
life upon Earth's surface.

* * * * *

It is difficult indeed to describe the appearance of a loose atomic
vortex to those who have never seen one; and, fortunately, most people
never have. And practically all of its frightful radiation lies in those
octaves of the spectrum which are invisible to the human eye. Suffice it
to say, then, that it had an average effective surface temperature of
about fifteen thousand degrees absolute--two and one-half times as hot
as the sun of Tellus--and that it was radiating every frequency possible
to that incomprehensible temperature, and let it go at that.

And Neal Cloud, scurrying in his flitter through that murky,
radiation-riddled atmosphere, setting up equations from the readings of
his various meters and gauges and solving those equations almost
instantaneously in his mathematical-prodigy's mind, sat appalled. For
the activity level was, and even in its lowest dips remained, far above
the level he had selected. His skin began to prickle and to burn. His
eyes began to smart and to ache. He knew what those symptoms meant; even
the flitter's powerful screens were not stopping all the radiation; even
his suit-screens and his special goggles were not stopping what leaked
through. But he wouldn't quit yet; the activity might--probably
would--take a nose-dive any instant. If it did, he'd have to be ready.
On the other hand, it might blow up at any instant, too.

There were two schools of mathematical thought upon that point. One held
that the vortex, without any essential change in its physical condition
or nature, would keep on growing bigger. Indefinitely, until, uniting
with the other vortices of the planet, it had converted the entire mass
of the world into energy.

The second school, of which the forementioned Carlowitz was the loudest
voice, taught that at a certain stage of development the internal energy
of the vortex would become so great that generation-radiation
equilibrium coul