“To the theory which we have just heard,” he said, “I have nothing to add; I can only apply it to the case of some comet already known. Let us suppose, for example, that a comet of the dimensions of that of should collide squarely with the Earth in its path about the Sun. The terrestrial ball would penetrate the nebula of the comet without experiencing any very sensible resistance. Admitting that this resistance is very slight, and that the density of the comet’s nucleus may be neglected, the passage of the Earth through the head of a comet of 1,800,000 kilometers in diameter, would require at least 25,000 seconds—that is, 417 minutes, or six hours, fifty-seven minutes—in round numbers, seven hours—the velocity being 120 times greater than that of a cannonball; and the Earth continuing to rotate upon its axis, the collision would commence about six o’clock in the morning.
“Such a plunge into the cometary ocean, however rarified it might be, could not take place without producing as a first and immediate consequence, by reason of the thermodynamic principles which have been just called to your attention, a rise in temperature such that probably our entire atmosphere would take fire! It seems to me that in this particular case the danger would be very serious.
“But it would be a fine spectacle for the inhabitants of Mars, and a finer one still for those of Venus. Yes, that would indeed be a magnificent spectacle, analogous to those we have ourselves seen in the heavens, but far more splendid to our near neighbors.
“The oxygen of the air would prove insufficient to maintain the combustion, but there is another gas which physicists do not often think of, for the simple reason that they have never found it in their analyses—hydrogen. What has become of all the hydrogen freed from the soil these millions of years which have elapsed since prehistoric times? The density of this gas being one-sixteenth that of the air, it must have ascended, forming a highly rarified hydrogen envelope above our atmosphere. In virtue of the law of diffusion of gases, a large part of this hydrogen would become mixed with the atmosphere, but the upper air layers must contain a considerable portion of it. There, doubtless, at an elevation of more than one hundred kilometers, the shooting stars take fire, and the aurora borealis is lighted. Notice here that the oxygen of the air would furnish the carbon of the comet ample material during collision to feed the celestial fire.
“Thus the destruction of the world will result from the combustion of the atmosphere. For about seven hours—probably a little longer, as the resistance to the comet cannot be neglected—there will be a continuous transformation of motion into a heat. The hydrogen and the oxygen, combining with the carbon of the comet, will take fire. The temperature of the air will be raised several hundred degrees; woods, gardens, plants, forests, habitations, edifices, cities, villages, will all be rapidly consumed; the sea, the lakes and the rivers will begin to boil; men and animals, enveloped in the hot breath of the comet, will die asphyxiated before they are burned, their gasping lungs inhaling only flame. Every corpse will be almost immediately carbonized, reduced to ashes, and in this vast celestial furnace only the heartrending voice of the trumpet of the indestructible angel of the Apocalypse will be heard, proclaiming from the sky, like a funeral knell, the antique death-song: ‘Solvet saeculum in favilla.’ This is what may happen if a comet like that of collides with the Earth.”
At these words the cardinal-archbishop rose from his seat and begged to be heard. The astronomer, perceiving him, bowed with a courtly grace and seemed to await the reply of his eminence.
“I do not desire,” said the latter, “to interrupt the honorable speaker, but if science announces that the drama of the end of the world is to be ushered in by the destruction of the heavens by fire, I cannot refrain from saying that this has always been the universal belief of the church. ‘The heavens,’ says St. Peter, ‘shall pass away with a great noise, and the elements shall meet with fervent heat, the Earth also and the works that are therein shall be burned up.’ St. Paul affirms also its renovation by fire, and we repeat daily at mass his words: ‘Eum qui venturus est judicare vivos et mortuos et saeculum per ignem.’ ”
“Science,” replied the astronomer, “has more than once been in accord with the prophecies of our ancestors. Fire will first devour that portion of the globe struck by the huge mass of the comet, consuming it before the inhabitants of the other hemisphere realize the extent of the catastrophe; but the air is a bad conductor of heat, and the latter will not be immediately propagated to the opposite hemisphere.
“If our latitude were to receive the first shock of the comet, reaching us, we will suppose, in summer, the tropic of Cancer, Morocco, Algeria, Tunis, Greece and Egypt would be found in the front of the celestial onset, while Australia, New Caledonia and Oceanica would be the most favored. But the rush of air into this European furnace would be such that a storm more violent than the most frightful hurricane and more formidable even than the air-current which moves continuously on the equator of Jupiter, with a velocity of 400,000 kilometers per hour, would rage from the Antipodes towards Europe, destroying everything in its path. The Earth, turning upon its axis, would bring successively into the line of collision, the regions lying to the west of the meridian first blasted. An hour after Austria and Germany it would be the turn of France, then of the Atlantic ocean, then of North America, which would enter somewhat obliquely the dangerous area about five or six hours after France—that is, towards the end of the collision.
“Notwithstanding
