Astounding Science Fiction, British Edition — page 81: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

WHIRLIGIG WORLD Y having five thousand times the mass of Earth once it had cooled below red heat—at first, that is. Later, when the rotational velocity increased almost to the point of real instability, it would be a different story; but we'll consider that in a moment. However, we have what seems to be a good reason to expect oceans of methane on this world; and with such oceans, it would be reasonable to expect the appearance and evolution of life forms using that liquid in their tissues. But just a moment. I admitted a little while ago that methane boils at a rather lower temperature than I wanted for this story. Is it too low? Can I raise it sufficiently by increasing - the atmospheric pressure, perhaps? Let’s see. The handbook lists meth- ane’s critical temperature as about minus eight-two degrees Centigrade. Above that temperature it will always be a gas, regardless of pressure ; and to bring its boiling point up nearly to that value, a pressure about forty-six times that of our own atmosphere at sea level will be needed. Well, we have a big planet, which should have held on to a lot of its original gases; it ought to have a pressure of hundreds or even thousands of atmospheres— whoops! we forgot something. At the equator, effective gravity— gravity minus centrifugal effect—is three times Earth normal. That, plus our specification of temperature and composition of the atmosphere, lets us compute the rate at which atmospheric density will decrease with altitude. It turns out that with nearly pure hydrogen, three g’s, and a tempera- ture of minus one hundred fifty for convenience, there is still a significant amount of atmosphere at six hundred miles altitude if we start at forty-odd bars for surface pressure—and at six hundred miles above the equator of this planet the centrifugal force due to its rotation balances the gravity! If there 79 had ever been a significant amount of atmosphere at that height, it would long since have been slung away into space; evidently we cannot possibly have a surface pressure anywhere near forty-six atmospheres. Some rough slide-rule work suggests eight atmos- pheres as an upper limit—I used summer temperatures rather than the annual mean. At that pressure methane boils at about minus one hundred forty-three degrees, and for some three hundred Earth days, or one sixth of each year, the planet will be in a position where its sun could reasonably be expected to boil its oceans. What to do? Well, Earth’s mean temperature is above the melting point of water, but considerable areas of our planet are permanently frozen. There is no reason why I can’t use the same effects for 61C; it is an observed fact that the axis of rotation of a planet can be oriented so that the equatorial and orbital planes do not coincide. I chose for story purposes to incline them at an angle of twenty-eight degrees, in such a direction that the northern - hemisphere’s midsummer occurs when the world is closest to its sun. This means that a large part of the northern hemisphere will receive no sunlight for fully three quarters of the year, and should in consequence develop avery respectable cap of frozen methane at the expense of the oceans in the other hemisphere. As the world approaches its sun the livable southern hemisphere is protected by the bulk of the planet from its deadly heat output; the star’s energy is expended in boiling off the north polar “ice” cap. Tremendous storms rage across the equator carrying air and methane vapor at a temperature little if any above the boiling point of the latter; and while the southern regions will warm up during their winter, they CONNIE OOOKS (e(0)