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Science today, as religion in the past, has become dogmatic - in the East as in the West. A scientist must swear loyalty to the established dogmas. The first rule of the scientific attitude is to study, then to think, and then to express an opinion. A reverse of this is not a scientific approach, and this is exactly what has been done by a group of scientists who have expressed opinions about my work. - Immanuel Velikovsky, quoted in Harvey Breit, "Talk with Mr. Velikovsky", The New York Times Review of Books, April 2, 1950, p.12.
VELIKOVSKY AND THE HEAT OF VENUS
Among the most unsettling of Immanuel Velikovsky's conclusions, based on his research for Worlds in Collision, was that the planet Venus must be a place of infernal heat.
He reasoned that, because of its youth and its history of violence ending only a few thousand years ago, Venus could still be so hot on the inside that energy it now receives from the Sun would have practically no influence on its surface temperature.
Although this suggestion confounded nearly everything professional astronomers then thought they knew of conditions on the Earth's nearest solar-system neighbor, scarcely half a dozen years were to pass between the publication of Worlds in Collision and the emergence of the first indications that its author was right and the astronomers wrong. And now that another 20 years have passed, it is clear not only that Velikovsky was right, but also that he was right for the right reason.
To many astronomers and planetologists, Velikovsky's line of reasoning, even today, seems perverse in the extreme. Discarding almost every tenet of uniformitarianism, the upstart cosmogonist, Velikovsky, claimed that Venus was born of Jupiter in a violent episode less than 10,000 years ago; that it passed uneventfully in and out of the inner solar system as a comet for a number of millennia; that about 35 centuries ago it came into near-contact with the Earth, and then repeated the feat only half a century later; that after another few centuries it ejected Mars from an earlier orbit (so that Mars, following a new elliptical path, began to menace the Earth); and that only since that time has it settled into its present orbit, safely positioned between those of Mercury and the Earth.
Little wonder that reviewers of Worlds in Collision were in many cases moved to suggest that Velikovsky's entrance upon the stage of astronomical science was every bit as calamitous as the events described in his book.
But Velikovsky himself was then, as now, willing to stake both his reputation and his work, to an important degree, on the implications that work held for Venus: That, despite its nearness and many superficial resemblances to the Earth (such as had led many astronomers to speak of Venus as the Earth's twin, or its sister planet), Venus must be a decidedly unearthly place-and, in particular, a world not yet cooled to the point where it could support life on its surface.
As pointed out in Worlds in Collision, a puzzling observation of the 1920's was that the dark hemisphere of Venus radiates at least as much heat as the sunlit hemisphere. To some students of the problem this suggested that Venus must rotate so rapidly that its nights are too brief for significant cooling to take place. This, at the time, was permissible speculation, since the planet's dense clouds prevented direct observation of its surface, and its period of rotation was therefore unknown.
But spectrographic evidence acquired about the same time appeared to rule out rapid rotation. Up to the very moment when Velikovsky's book was published, the seemingly conflicting thermal and spectrographic observations constituted a scientific mystery.
Velikovsky, however, reasoned that the mystery itself must be illusory--that it stemmed from erroneous preconceptions of a solar system without a recent history. He wrote: "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. . . . Since [Venus was involved in so many violent events] between the third and first millennia before the present era, the core of the planet Venus must still be hot" (emphasis added).
In 1950, of course, astronomers would have none of it. But by 1956 the accepted picture of Venus began to change. In the spring of that year, to the surprise of all but Velikovsky, radio astronomers reading signals from deep in the atmosphere of the planet found that temperatures there were, as they cautiously described them, "higher than [that of] boiling water" (New York Times, June 5, 1956).
Suddenly the planet Venus became the object of renewed interest on the part of professional observers. During the next 10 years, each successive set of observations seemed to add to the mystery by increasing previous estimates of the surface temperature, until finally a figure close to 900°F seemed inescapable. (This has been repeatedly confirmed by Soviet Venera landers, most recently by Venera 9 and Venera 10 in the fall of 1975.) Here was clear vindication for Velikovsky's advance claim, as stated in his discussion of "The Thermal Balance of Venus" (Worlds in Collision). Yet recognition was not forthcoming, and is now at least 10--more nearly 15--years overdue.
Almost from the start, Velikovsky's detractors have displayed a penchant for ducking this issue by arguing that his term, "hot," is not quantitative enough to warrant recognition of a prior claim on his part. An early instance of this appears in an article written in the early sixties by Donald H. Menzel, then director of Harvard College Observatory ("The Debate over Velikovsky," Harper's, December 1963): "As to the 'high temperature' of Venus, 'hot' is only a relative term. For example, liquid air is hot, relative to liquid helium; the sun's surface is cold, relative to the star Sirius, and so on. Hence, to see what Velikovsky implied by 'hot' we turn to his own work, Worlds in Collision, last chapter. Here he refers to actual astronomical observations of the infrared radiation from Venus, which showed that the dark side of Venus was just as hot as the sunlit side. The measured temperatures were comfortably warm, not 800°F."
Aside from the inference that the temperatures deduced from infrared observations--something like 25 below zero, Fahrenheit-are "comfortably warm," Menzel's remarks are true enough. But the Harvard astronomer carefully obscures the issue by stating one fact too many. The infrared radiation, which comes from the tops of the clouds, not the surface, indeed indicates that temperatures there are far from "hot." The precise values of such temperatures, however, are irrelevant; what counts, and what Velikovsky was calling attention to, is the fact that daytime and nighttime temperatures at the tops of the clouds are, for all practical purposes, identical. And, if the planet rotates slowly, as the spectrographic evidence suggests, and as has now been established by radar astronomers, then the near-uniformity of cloudtop temperatures over the entire globe implies that the source of heat maintaining those temperatures is not the Sun, but is, instead, a "hot" body concealed within the clouds.
Menzel is correct in suggesting that one should turn to Velikovsky's own writings to see what he means by "hot." But in this context, the astronomer's remarks are seen to be distracting at best. Velikovsky's term, "hot," turns out to be a most judicious choice. Had he yielded to any passing impulse to guess at the exact temperature of the surface of Venus, he would surely have been criticized for drawing a conclusion far too specific for the quality of his data.
From any objective point of view, Velikovsky's entire treatment of the claim that Venus must still be "hot" makes abundantly clear what range of heat he had in mind. His sources describe the protoplanet as incandescent, rivaling the Sun in brightness, only a few thousand years ago; this puts an upper limit of some few thousands of degrees on the problem, if one assumes that since the end of interplanetary violence in the first millennium B.C. Venus has been cooling off. In another connection, also in Worlds in Collision ("The Gases of Venus"), he writes: "On the basis of this research, I assume that Venus must be rich in petroleum gases. If and as long as Venus is too hot for the liquefaction of petroleum, the hydrocarbons will circulate in gaseous form." The characteristics of many common hydrocarbons are such that, at atmospheric pressure on Earth, temperatures in the hundreds of degrees Fahrenheit are required to "boil" them; on Venus, where the surface atmospheric pressure is said to be about 90 times that on Earth, distillation temperatures would be correspondingly higher. But, even without crediting Velikovsky with any advance claim as to atmospheric pressures on Venus, one must assume that he was thinking in terms of temperatures higher than that of boiling water at sea level on Earth. Therefore, it would seem reasonable to credit the author of Worlds in Collision with the prediction, more than a quarter-century ago, that the surface temperature of Venus, the "newcomer," would ultimately be found to range, in our day, close to 1000°F. It is to his credit, nonetheless, that he refrained from offering such a specific; in any case his anticipations, based on an entirely new approach to the problem of Solar System history, set him quite apart from all other students of the subject.
As early as 1940, at least one astronomer considered the possibility that the surface of Venus might be rather warm. Rupert Wildt of Yale University Observatory suggested (Astrophysical Journal 91, 266) that the carbon dioxide known to be abundant in the planet's atmosphere might trap solar radiation--that is, admit visible sunlight, but inhibit the escape of infrared rays emitted by sunlight-heated surface materials-and thus, through a "greenhouse effect," produce higher "air" temperatures than would otherwise be expected. Wildt estimated that the surface temperatures might reach 275°F.
But even this moderately high estimate was not accepted by Wildt's colleagues. Gerard Kuiper later refined the calculations and came up with 170°F as the maximum temperature likely to be due to a greenhouse effect on Venus.
In the late 1950's and early 1960's, as it gradually but unmistakably became apparent that Venus is really much hotter than any professional astronomer had ever imagined, the greenhouse theory was resurrected and modified in various attempts to account for the heat of Venus in nonVelikovskian terms. In 1960, Carl Sagan, then at Yerkes Observatory, proposed an "enhanced" greenhouse effect (Astronomical Journal 65, 352), and a decade later S.I. Rasool and C. de Bergh suggested (Nature 226, 1037) that perhaps a "runaway" greenhouse effect was responsible. Both these hypotheses, however, depend upon the presence of a significant amount of water vapor in the atmosphere of Venus-vapor which is simply postulated, without supporting evidence, to exist.
Sagan, in his recent book, The Cosmic Connection (Doubleday, 1973), clings firmly to his own hypothesis and states categorically that Venus is heated by a greenhouse mechanism-and that both carbon dioxide and water are available to do the job (p. 51). Only slightly less self-assured were his comments on the same subject at the AAAS symposium on " Velikovsky's Challenge to Science" (San Francisco, 1974): "The atmosphere [of Venus] ... is composed primarily of carbon dioxide. The large abundance of carbon dioxide, plus the smaller quantities of water vapor which have been detected on Venus, are adequate to heat the surface to the observed temperature via the greenhouse effect."
Sagan went on: "The Venera 8 descent module, the first spacecraft to land on the illuminated hemisphere of Venus, found it light at the surface, and the Soviet experimenters concluded that the amount of light reaching the surface and the atmospheric constitution were together adequate to drive the required radiative-convective greenhouse. Velikovsky is certainly mistaken when he says 'light does not penetrate the cloud cover' and is probably mistaken when he says 'greenhouse effect could not explain so high a temperature'."
One must ask, however: How convincing are the Venera 8 results? The craft landed at a point on Venus where the Sun at the moment was only about six degrees above the horizon. The investigators reported that the light was very dim, indeed. But they concluded that the average illumination over the sunlit hemisphere ought to be about five times the detected illumination. And, on the basis of such a fivefold amplification of their actual findings, they concluded that Sagan's greenhouse mechanism is feasible (cf., M. Ya. Marov et al., Icarus 20, 407, 1973).
Others were not so sure. A. A. Lacis and J. E. Hansen of Goddard Institute for Space Studies reviewed the Venera 8 findings and described them as so ambiguous as to leave many important questions unanswered, and in particular those most pertinent to the question of the importance of the greenhouse effect on Venus (cf. Science 184, 979, 31 May 1974).
In late October 1975, the Soviet probes Venera 9 and 10 secured man's first photographs of the surface of Venus. Certain angular rocks in Venera 9's approach photograph appear to cast such sharp shadows that it is difficult to believe that the source of light was sunlight diffused through heavy clouds and attenuated to about one percent of its intensity in space at the orbit of Venus; yet the Venera 8 experimenters declared earlier that just such attenuation could be attributed to the clouds of Venus. As Science News reported (November 1, 1975), "Soviet officials gave no immediate indication of whether the landing craft carried their own lighting, or even of the wavelengths at which the images were made." So the nature, as well as the source, of the light used to photograph the planet's surface remains very much in doubt.
Sunlight may or may not penetrate to the surface of Venus. If it actually does so, what of the water vapor required by the greenhouse model to do the job of trapping infrared radiation from the surface, thus raising the temperature of the surface environment to 900°F?
Following an intensive microwave study of Venus, M. A. Janssen and several colleagues at the Radio Astronomy Laboratory of the University of California at Berkeley reported (Science 179, 994, 9 March 1973) that they found "no evidence of water vapor in the lower atmosphere of Venus." They added that "it remains to be shown that a 'greenhouse' mechanism can be supported with the present constraints on the water vapor content."
As of today, two of the most important postulates of the greenhouse model-sunlight of consequence reaching the surface of Venus, and water vapor of detectable quantities in the lower atmosphere of the planet-remain questionable. And there is another problem, seldom mentioned by proponents of greenhouse hypotheses, that is just as important to the maintenance of their stance.
Were sunlight actually the source of the heat of Venus, the input of energy would always be confined largely to the sunlit hemisphere. Since Venus rotates so slowly that one of its nights is as long as two months on Earth, it is reasonable to expect, as I. I. Shapiro has pointed out (Science 159, 1124, 8 March 1967), "larger temperature differentials between day and night" on Venus than on Earth. Even if some of the heat were convected and conducted to the dark side of the planet, considerably less than 100-percent efficiency would characterize the process. The dark side would necessarily remain cooler, on the average, than the sunlit side. Yet this is apparently not the case.
Pettit and Nicholson, observing infrared radiation from the cloud tops in the 1920's, actually found the dark hemisphere a few degrees warmer than the sunlit side. Venera 7, landing on the dark side, reported a surface temperature a few degrees higher than that reported about the same time from the daylight zone by Venera 8. Neither of these sets of observations supports the greenhouse model.
This problem was at least tacitly acknowledged by Sagan a few years ago when, at his behest, David Morrison, then connected with Harvard College Observatory and Smithsonian Astrophysical Observatory, undertook to settle it with intensive observations of Venus' radio emission at various phases of illumination by the Sun. After "more than 100 hours of observing time," Morrison reported (Science 163, 815, 21 February 1969) that he could find no phase effect. Although his experiment was designed to read temperatures below the surface of the planet, where nighttime cooling would be expected in the frame of the greenhouse hypothesis, he interpreted his null result in a rather unusual way: The radiation he monitored-at a wavelength of 1.95 centimeters-must, contrary to the careful anticipations of both himself and Sagan, originate 11 primarily in the lower atmosphere and not in the subsurface of the planet." On this basis, he termed his findings "not surprising," and he concluded his report with the rather lame suggestion that "it is still possible to expect a phase effect at wavelengths longer than 5 cm, where, according to recent atmospheric models . . . the radiation arises primarily in the subsurface of Venus rather than in the atmosphere."
In the years since Morrison's report appeared, however, no such phase effect has yet been observed, and the greenhouse model rests in limbo on this score, too. Nonetheless, in 1974 Morrison spoke at the Pensee-McMaster University symposium on " Velikovsky and the Recent History of the Solar System" and insisted: "Those who have made recent quantitative studies of the mechanism for producing such high temperatures [on Venus] are virtually all in agreement that the high infrared opacity of the atmosphere provides the explanation (the 'greenhouse effect')." Morrison neglected to mention that his own investigation of an important corollary to the greenhouse hypothesis had cast strong doubt on the entire premise.
British astronomer V. A. Firsoff has ridiculed the greenhouse model from another point of view (Astronomy and Space, vol. 2, no. 3, 1973):"Increasing the mass of the atmosphere may intensify the greenhouse effect, but it must also reduce the proportion of solar energy reaching the surface, while the total of the available energy must be distributed over a larger mass and volume. Indeed, if the atmosphere of Venus amounts to 75 air-masses, . . . the amount of solar energy per unit mass of this atmosphere will be about 0.01 of that available on the Earth. Such an atmosphere would be strictly comparable to our seas and remain stone-cold, unless the internal heat of Venus were able to keep it at temperatures corresponding to the brightness temperatures derive from the microwave emission" (emphasis added).
Now Firsoff seems in no sense to be a supporter of Velikovsky. (Indeed, at the time he wrote these words, Soviet probes had not yet landed on Venus, and he apparently preferred to deny the radiometric evidence that the surface of the planet is hot.) But his observation is entirely pertinent: If the surface of Venus has a temperature of 900°F, the only physically sound explanation is that an outflow of internal heat is taking place at a rate sufficient to maintain that temperature. It is quite likely that the dense atmosphere and clouds serve to inhibit the escape of heat from the surface. But in any case ground temperatures below the surface must be in excess of 900°F to provide a temperature gradient along which internal heat flows outward.
From any reasonable analysis of the available evidence, we appear to be left with Velikovsky's as the only viable explanation yet put forward: Venus is not billions of years old; it is apparently so young that it has not yet cooled enough for "comfortable" surface temperatures to become established, and therefore solar-energy input has little or no influence upon its surface environment.