THE RESTLESS SUN

Evening Post, Volume CXI, Issue 138, 13 June 1931, Page 22

THE RESTLESS SUN

If ever rocket-travelling through space,becomes common, ,tho mountains of the moon ought to form a perfect paradise for climbers, writes Sir James -Jeans in the Melbourne "Argus."' Tho sun casts shadows of the jagged lunar mountains on the flat deserts below, and even in a small telescope one can see wonderful needles, pinnacles, and arretes. But this is not the only attraction the lunar mountains have to offer: on the moon tho force of gravity is only a sixth as great as on the earth, so that a climber could climb six times as high without getting tired, and fall six times as -far without getting hurt. But he must remember to take supplies of oxygen with him, for the moon has no atmosphere, because its gravitational pull is not strong enough to retain one. The earth has a strong gravitational pull; its atmosphere consists of millions of millions of molecules darting about with quite high speeds of hundreds of yards a, second, and even miles a second. But the molecules never attain high enough speeds to be able to jump away from the earth altogether—like our rocket did. They always fall back like a cricket ball. The moon, with' its weaker gravitational hold, has seen the molecules of its atmosphere escaping from it, one by one, until it has almost no atmosphere left.

If we should happen to pass near Venus on our journey we should see nothing specially interesting. It is about the size of the earth, but is completely enveloped in clouds. But Mercury ought to provide an arresting spectaclei. It has.little or no atmosphere, so that its scenery should stand out in vivid relief, like that of the moon. Mercury always turns the same face to the sun, just as the moon always turns the same face to the earth, and for the same reason; the firm gravitational grip of the larger body has checked its efforts at turning round. Now the face \vhich Mercury turns to the sun, being for ever baked in a, cloudless atmosphere by a sun which is very near indeed, is naturally very hot and parch-

HEAVENS' POWER STATION

cd. .A "place in the sun" on Mercuryis just about as hot as a place on a grill over a very hot lire, so that if there are any rivers on Mercury they must be of molten lead or some such substance. ' And now, as we get near to the 6un, we begin to have a fine view of its surface. ."We see at once it is no dead world, like the moon or Mercury. Nothing seems at rest; the whole surface is agitated, boiling and erupting in various ways. The interior of the sun is a huge power-staj,ion, which works continuously, generating energy which is driven outward to its surface and pours away into space in the form of radiation. Each square inch of surface receives 50 h.p. of-energy, which it has to get rid of somehow or, other. It cannot do this by simply lying still at rest. Everywhere we see it boiling up —the topmost layers, so to speak, turning over and presenting their hottest sides to outer space, so that the imprisoned radiation may pour away the more rapidly. Even this is not, enough, for here and there we see huge fountains of flame, called "Prominences," spouting up hundreds of thousands o£ miles above the sun's surface. It is as if the sun's surface could not get rid of energy as rapidly as it arrived from inside, and so created this extra mechanism of fountains, cascades, and arches of flame to help it. These arc generally of a crimson colour, and often take the most fantastic shapes. .Some stand almost still, as if roote,d in the body of the sun; others, sprout up like Jack's, beanstalk, with speeds of thousands of mileg a second. Some jump clear of,the sun altogether to heights of ' hundreds of thousands of miles, changing their: shapes all the time. A prominence which starts up in the shape ,of a huge rod mushroom may come down looking like a mangrove tree, or a fierce crimson dog, or a still more weird antediluvian animal. One photographed, at the eclipse of 1919 looked for all the world like an anteater, 350,000 miles from snout to tail—the size of animal that could gulp down-the whole earth like a pill. : . .