Broca's Brain: The Romance of Science

Collision. On page 364 Velikovsky argues that the near-collisions of Mars with Earth and Venus “make it highly improbable that any higher forms of life, if they previously existed there, survived on Mars.” But when we examine the Mars as seen by Mariner 9 and Viking 1 and 2, we find that something over one-third of the planet has a modified cratered terrain somewhat reminiscent of the Moon and displays no sign of spectacular catastrophes other than ancient impacts. The other half to two-thirds of the planet shows almost no sign whatever of such impacts, but instead displays dramatic evidence of major tectonic activity, lava flows and vulcanism about a billion years ago. The small but detectable amount of impact cratering in this terrain shows that it was made much longer than several thousand years ago. There is no way to reconcile this picture with a view of a planet recently so devastated by impact catastrophism that all intelligent life would thereby have been eliminated. It is also by no means clear why, if all life on Mars were to be exterminated in such encounters, all life on Earth was not similarly exterminated.

PROBLEM VI. MANNA

MANNA, according to the etymology in Exodus, derives from the Hebrew words man-hu, which means “What is it?” Indeed, an excellent question! The idea of food falling from comets is not absolutely straightforward. Optical spectroscopy of comet tails, even before Worlds in Collision was published (1950), showed the presence of simple fragments of hydrocarbons, but no aldehydes-the building blocks of carbohydrates-were known then. They may nevertheless be present in comets. However, from the passage of Comet Kohoutek near the Earth, it is now known that comets contain large quantities of simple nitriles-in particular, hydrogen cyanide and methyl cyanide. These are poisons, and it is not immediately obvious that comets are good to eat.

But let us put this objection aside, grant Velikovsky his hypothesis, and calculate the consequences. How much manna is required to feed the hundreds of thousands of Children of Israel for forty years (see Exodus, Chapter 16, Verse 35)?

In Exodus, Chapter 16, Verse 20, we find that the manna left overnight was infested by worms in the morning-an event possible with carbohydrates but extremely unlikely with hydrocarbons. Moses may have been a better chemist than Velikovsky. This event also shows that manna was not storable. It fell every day for forty years according to the Biblical account. We will assume that the quantity that fell every day was just sufficient to feed the Children of Israel, although Velikovsky assures us (page 138) from Midrashic sources that the quantity that fell was adequate for two thousand years rather than a mere forty. Let us assume that each Israelite ate on the order of a third of a kilogram of manna per day, somewhat less than a subsistence diet. Then each will eat 100 kilograms per year and 4,000 kilograms in forty years. Hundreds of thousands of Israelites, the number explicitly mentioned in Exodus, will then consume something over a million kilograms of manna during the forty years’ wandering in the desert. But we cannot imagine the debris from the cometary tail falling each day, [7] preferentially on the portion of the Wilderness of Sin in which the Israelites happened to have wandered. This would be no less miraculous than the Biblical account taken at face value. The area occupied by a few hundred thousand itinerant tribesmen, wandering under a common leadership, is, very roughly, several times 10^?7 the area of the Earth. Therefore, during the forty years of wandering, all of the Earth must have accumulated several times 10¹⁸ grams of manna, or enough to cover the entire surface of the planet with manna to a depth of about an inch. If this indeed happened, it would certainly be a memorable event, and may even account for the gingerbread house in “Hansel and Gretel.”

Now, there is no reason for the manna to have fallen only on Earth. In forty years the tail of the comet, if restricted to the inner solar system, would have traversed some 10¹⁰ km. Making only a modest allowance for the ratio of the volume of the Earth to the volume of the tail, we find that the mass of manna distributed to the inner solar system by this event is larger than 10²⁸ grams. This is not only more massive by many orders of magnitude than the most massive comet known; it is already more massive than the planet Venus. But comets cannot be composed only of manna. (Indeed, no manna at all has been detected so far in comets.) Comets are known to be composed primarily of ices, and a conservative estimate of the ratio of the mass of the comet to the mass of the manna is much larger than 10³. Therefore, the mass of the comet must be much larger than 10³¹ grams. This is the mass of Jupiter. If we were to accept Velikovsky’s Midrashic source above, we would deduce that the comet had a mass comparable to that of the Sun. Interplanetary space in the inner solar system should even today be filled with manna. I leave it to the reader to make his own judgment on the validity of Velikovsky’s hypothesis in the light of such calculations.

PROBLEM VII. THE CLOUDS OF VENUS

VELIKOVSKY’S prognostication that the clouds of Venus were made of hydrocarbons or carbohydrates has many times been hailed as an example of a successful scientific prediction. From Velikovsky’s general thesis and the calculations just described above, it is clear that Venus should be saturated with manna, a carbohydrate. Velikovsky says (page x) that “the presence of hydrocarbon gases and dust in the cloud envelope of Venus would constitute a crucial test” for his ideas. It is also not clear whether “dust” in the foregoing quotation refers to hydrocarbon dust or just ordinary silicate dust. On the same page Velikovsky quotes himself as saying, “On the basis of this research, I assume that Venus must be rich in petroleum gases,” which seems to be an unambiguous reference to the components of natural gas, such as methane, ethane, ethylene and acetylene.

At this point, a little history must enter our story. In the 1930s and early 1940s, the only astronomer in the world concerning himself with planetary chemistry was the late Rupert Wildt, once of Gottingen, and later at Yale. It was Wildt who first identified methane in the atmospheres of Jupiter and Saturn, and it was he who first proposed the presence of higher hydrocarbon gases in the atmospheres of these planets. Thus, the idea that “petroleum gases” might exist on Jupiter is not original with Velikovsky. Likewise, it was Wildt who proposed that formaldehyde might be a constituent of the atmosphere of Venus, and that a carbohydrate polymer of formaldehyde might constitute the clouds. The idea of carbohydrates in the clouds of Venus was not original with Velikovsky either, and it is difficult to believe that one who so thoroughly researched the astronomical literature of the 1930s and 1940s was unaware of these papers by Wildt which relate so closely to Velikovsky’s central theme. Yet there is no mention whatever of the Jupiter phase of Wildt’s work and only a footnote on formaldehyde (page 368), without references, and without any acknowledgment that Wildt had proposed carbohydrates on Venus. Wildt, unlike Velikovsky, understood well the difference between hydrocarbons and carbohydrates; moreover, he performed unsuccessful spectroscopic searches in the near-ultraviolet for the proposed formaldehyde monomer. Being unable to find the monomer, he abandoned the hypothesis in 1942. Velikovsky did not.

As I pointed out many years ago (Sagan, 1961), the vapor pressure of simple hydrocarbons in the vicinity of the clouds of Venus should make them detectable if they comprise the clouds. They were not detectable then, and in the intervening years, despite a wide range of analytic techniques used, neither hydrocarbons nor carbohydrates have been found. These molecules have been searched for by high-resolution ground-based optical spectroscopy, including Fourier transform techniques; by ultraviolet spectroscopy from the Wisconsin Experimental Package of the Orbiting Astronomical Observatory OAO-2; by ground-based infrared observations; and by direct entry probes of the Soviet Union and the United States. Not one of them has been found. Typical abundance upper limits on the simplest hydrocarbons and on aldehydes, the building blocks of carbohydrates, are a few parts per million (Connes, et al., 1967; Owen and Sagan, 1972). [The corresponding upper limits for Mars are also a few parts per million (Owen and Sagan, 1972)]. All observations are consistent in showing that the bulk of the Venus atmosphere is composed of carbon dioxide. Indeed, because the carbon is present in such an oxidized form, at best trace constituents of the simple reduced hydrocarbons could be expected. Observations on the wings of the critical 3.5 micron region show not the slightest trace of the C-H absorption feature common to both hydrocarbons and carbohydrates (Pollack, et al., 1974). All other absorption bands in the Venus spectrum, from the ultraviolet through the infrared, are now understood; none of them is due to hydrocarbons or