2 These figures are from Arrhenius, Das Schicksal der Planeten (1911), p. 6. E. A. Antoniadi (La planete Mercure [1939], p. 49) gives 0.63 for Venus, 0.17 for Mars, and 0.10 for the moon.
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The Thermal Balance of Venus
Radiometric observations at the Mount Wilson and Flagstaff observatories in 1922 have shown that "a considerable amount of heat" is emitted by the dark part of the disc of the planet Venus.
Venus, being nearer to the sun than the earth, turns in succession its illuminated and shaded parts toward the earth: it shows phases like the moon. The temperature of the day and night sides of Venus was measured by a radiometric method and it was found that there is "a nearly uniform temperature over the planet's surface both on the illuminated and dark hemispheres." "This sentence [of E. Pettit and S. B. Nicholson] is a terse statement of what is perhaps the most valuable single discovery ever made with respect to the planet Venus." * Similar results were also obtained independently and almost simultaneously by a second pair of researchers.2
What explanation can be given for the phenomenon of the nearly uniform temperature of the day and night hemispheres of Venus? The conclusion drawn was this: The daily rotation of the planet Venus is very rapid and during the short night the temperature cannot fall to any considerable extent. But this conclusion stands in complete contradiction to what was believed to be the established fact of the nonrotation of Venus (with respect to the sun, or of a rotation in relation to the fixed stars with a period equal to the time of one revolution on its planetary orbit or 225
terrestrial days). Due to the cover of clouds over Venus, it is impossible to have a direct impression as to whether Venus has a day-night rotation or not. The spectro-graphic data suggest that the planet revolves always with the same side to the sun, just as the moon revolves always with the same side to the earth, or that, at most, it rotates very slowly.3 In any case, a short period of rotation is excluded by the spectrographic data.
"If the period of rotation of Venus is 225 days, as many observers
1 F. E. Ross, "Photographs of Venus," Contributions from the Mount Wilson Observatory, No.
363 (1928).
2 Coblentz and Lampland, lournal of Franklin Institute, Vol. 199 (1925), 804. 8 E. St. John and S. B. Nicholson, "The Spectrum of Venus," Astraphysical Journal, Vol. LVI (1922).
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have been led to believe, it is difficult to see how the high temperature of the rotating layer of the night side can be maintained." 4
Compromise does not satisfy either side. Neither the radiometric data, which suggest a short period of rotation, nor the precise spec-troscopic data, which indicate a long period of rotation, may be ignored, and "they will undoubtedly furnish material for discussion and debate for many years." "
In reality there is no conflict between the two methods of physical observation. The night side of Venus radiates heat because Venus is hot. The reflecting, absorbing, insulating, and conducting properties of the cloud layer of Venus modify the heating effect of the sun upon the body of the planet; but at the bottom of the problem lies this fact: Venus gives off heat.
Venus experienced in quick succession its birth and expulsion under violent conditions; an existence as a comet on an ellipse which approached the sun closely; two encounters with the earth accompanied by discharges of potentials between these two bodies and with a thermal effect caused by conversion of momentum into heat; a number of contacts with Mars, and probably also with Jupiter. Since all this happened between the third and first millennia before the present era, the core of the planet Venus must still be hot. Moreover, if there is oxygen present on Venus, petroleum fires must be burning there.
These conclusions are drawn from the history of Venus as established in this research.
The End
This world will be destroyed; also the mighty ocean will dry up; and this broad earth will be burnt up. Therefore, sirs, cultivate friendliness; cultivate compassion.
—"World Cycles" in Visuddhi-Magga The solar system is not a structure that has remained unchanged for billions of years; displacement of members of the system oc-* Ross, "Photographs of Venus," p. 14. B Ibid.
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curred in historical times. Nor is there justification for the excuse that man cannot know or find out how this system came into being because he was not there when it was arranged in its present pattern.
Catastrophes have repeatedly reduced civilization on this earth to ruins. But our earth has fared well in comparison with Mars; and judged by the state of civilization at which mankind has arrived, conditions for life processes have been improved in some respects. But if events of this kind happened in the past, they may happen again in the future, with perhaps a different—fatal—
result.
The earth has come in contact with other planets and comets. At present no planet has a course that endangers the earth, and only a few asteroids—mere rocks, a few kilometers in diameter—
have orbits that cross the path of the earth. This was discovered, to the amazement of scholars, only recently. But in the solar system there exists a possibility that at some date in the future a collision between two planets will occur, not a mere encounter between a planet and an asteroid.
The orbit of Pluto, the farthest of the planets from the sun, though much larger than Neptune's, crosses that of Neptune. True, the plane of the orbit of Pluto is inclined 17° to the ecliptic, and therefore the danger of a collision is not impending. However, since the long axis of Pluto's orbit changes its direction, future contact between the two planets is probable if no comet intervenes to disrupt the intersecting orbits of these bodies. Astronomers will see the planets stop or slow down in their rotation, cushioned in the magnetic fields about them; a spark will fly from one planet to another, and thus an actual crushing collision of the lithospheres will be avoided; then the planets will part and change their orbits. It may happen that Pluto will become a satellite of Neptune. There is also the possibility that Pluto may encounter, not Neptune, but Triton, Neptune's satellite and about one-third as large as Pluto. Whether Pluto will become another moon of Neptune or will be thrown into a position much closer to the sun, or whether it will free Triton from being a satellite are matters of conjecture.
Another case of intersection may be found among the moons of Jupiter. The orbit of the sixth satellite is interlocked with the orbit of the seventh, and the eighth satellite is highly erratic and crosses
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the path of the ninth. One should be able to calculate how long the sixth and seventh satellites have moved on their present paths; the figures will probably not be large.
Each collision between two planets in the past caused a series of subsequent collisions, in which other planets became involved. The collision between major planets, which is the theme of the sequel to Worlds in Collision, brought about the birth of comets. These comets moved across the orbits of other planets and collided with them. At least one of these comets in historical times became a planet (Venus), and this at the cost of great destruction on Mars and on the earth.
Planets, thrown off their paths, collided repeatedly until they attained their present positions, where their orbits do not intersect. The only remaining cases of intersection are those of Neptune and Pluto, the satellites of Jupiter, and some planetoids (asteroids) that cross the orbits of Mars and the earth.