Pebble in the Sky by Isaac Asimov (iphone ebook reader txt) 📕

after contact with its velvet—“perhaps it is unique in that way. It’s an unenviable distinction.”

“But it is not just a question of statistical uniqueness.” Arvardan spoke deliberately between occasional sips. “It goes further; it has tremendous potentialities. Biologists have shown, or claim to have shown, that on planets in which the intensity of radioactivity in the atmosphere and in the seas is above a certain point life will not develop. . . . Earth’s radioactivity is above that point by a considerable margin.”

“Interesting. I didn’t know that. I imagine that this would constitute definite proof that Earth life is fundamentally different from that of the rest of the Galaxy. . . . That should suit you, since you’re from Sirius.” He seemed sardonically amused at this point and said in a confidential aside, “Do you know that the biggest single difficulty involved in ruling this planet lies in coping with the intense anti-Terrestrialism that exists throughout the entire Sirius Sector? And the feeling is returned with interest on the part of these Earthmen. I’m not saying, of course, that anti-Terrestrialism doesn’t exist in more or less diluted form in many places in the Galaxy, but not like on Sirius.”

Arvardan’s response was impatient and vehement. “Lord Ennius, I reject the implication. I have as little intolerance in me as any man living. I believe in the oneness of humanity to my very scientific core, and that includes even Earth. And all life is fundamentally one, in that it is all based upon protein complexes in colloidal dispersion, which we call protoplasm. The effect of radioactivity that I just talked of does not apply simply to some forms of human life, or to some forms of any life. It applies to all life, since it is based upon the quantum mechanics of the protein molecules. It applies to you, to me, to Earthmen, to spiders, and to germs.

“You see, proteins, as I probably needn’t tell you, are immensely complicated groupings of amino acids and certain other specialized compounds, arranged in intricate three-dimensional patterns that are as unstable as sunbeams on a cloudy day. It is this instability that is life, since it is forever changing its position in an effort to maintain its identity—in the manner of a long rod balanced on an acrobat’s nose.

“But this marvelous chemical, this protein, must be first built up out of inorganic matter before life can exist. So, at the very beginning, by the influence of the sun’s radiant energy upon those huge solutions we call oceans, organic molecules gradually increase in complexity from methane to formaldehyde and finally to sugars and starches in one direction, and from urea to amino acids and proteins in another direction. It’s a matter of chance, of course, these combinations and disintegrations of atoms, and the process on one world may take millions of years while on another it may take only hundreds. Of course it is much more probable that it will take millions of years. In fact, it is most probable that it will end up never happening.

“Now physical organic chemists have worked out with great exactness all the reaction chain involved, particularly the energetics thereof; that is, the energy relationships involved in each atom shift. It is now known beyond the shadow of a doubt that several of the crucial steps in the building of life require the absence of radiant energy. If this strikes you as queer, Procurator, I can only say that photochemistry (the chemistry of reactions induced by radiant energy) is a well-developed branch of the science, and there are innumerable cases of very simple reactions which will go in one of two different directions depending upon whether it takes place in the presence or absence of quanta of light energy.

“In ordinary worlds the sun is the only source of radiant energy, or, at least, by far the major source. In the shelter of clouds, or at night, the carbon and nitrogen compounds combine and recombine, in the fashions made possible by the absence of those little bits of energy hurled into the midst of them by the sun—like bowling balls into the midst of an infinite number of infinitesimal tenpins.

“But on radioactive worlds, sun or no sun, every drop of water—even in the deepest night, even five miles under—sparkles and bursts with darting gamma rays, kicking up the carbon atoms—activating them, the chemists say—and forcing certain key reactions to proceed only in certain ways, ways that never result in life.”

Arvardan’s drink was gone. He placed the empty glass on the waiting cabinet. It was withdrawn instantly into the special compartment where it was cleaned, sterilized, and made ready for the next drink.

“Another one?” asked Ennius.

“Ask me after dinner,” said Arvardan. “I’ve had quite enough for now.”

Ennius tapped a tapering fingernail upon the arm of his chair and said, “You make the process sound quite fascinating, but if all is as you say, then what about the life on Earth? How did it develop?”

“Ah, you see, even you are beginning to wonder. But the answer, I think, is simple. Radioactivity, in excess of the minimum required to prevent life, is still not necessarily sufficient to destroy life already formed. It might modify it, but, except in comparatively huge excess, it will not destroy it. . . . You see, the chemistry involved is different. In the first case, simple molecules must be prevented from building up, while in the second, already-formed complex molecules must be broken down. Not at all the same thing.”

“I don’t get the application of that at all,” said Ennius.

“Isn’t it obvious? Life on Earth originated before the planet became radioactive. My dear Procurator, it is the only possible explanation that does not involve denying either the fact of life on Earth or enough chemical theory to upset half the science.”

Ennius gazed at the other in amazed disbelief. “But you can’t mean that.”

“Why not?”

“Because how can a world become radioactive? The life of the radioactive elements in the planet’s crust are in the millions and billions of