Broca's Brain - Carl Sagan [69]
PROBLEM X
THE CIRCULARIZATION OF THE
ORBIT OF VENUS AND
NONGRAVITATIONAL FORCES
IN THE SOLAR SYSTEM
THE IDEA that Venus could have been converted, in a few thousand years, from an object in a highly elongated or eccentric orbit to its present orbit, which is—except for Neptune—the most nearly perfect circular orbit of all the planets, is at odds with what we know about the three-body problem* in celestial mechanics. However, it must be admitted that this is not a completely solved problem, and that, while the odds are large, they are not absolutely overwhelming against Velikovsky’s hypothesis on this score. Furthermore, when Velikovsky invokes electrical or magnetic forces, with no effort to calculate their magnitude or describe in detail their effects, we are hard pressed to assess his ideas. However, simple arguments from the required magnetic energy density to circularize a comet show that the field strengths implied are unreasonably high (Appendix 4)—they are counterindicated by studies of rock magnetization.
We can also approach the problem empirically. Straightforward Newtonian mechanics is able to predict with remarkable accuracy the trajectories of spacecraft—so that, for example, the Viking orbiters were placed within 100 kilometers of their designated orbit; Venera 8 was placed precisely on the sunlit side of the equatorial terminator of Venus; and Voyager 1 was placed in exactly the correct entry corridor in the vicinity of Jupiter to be directed close to Saturn. No mysterious electrical or magnetic influences were encountered. Newtonian mechanics is adequate to predict, with great precision, for example, the exact moment when the Galilean satellites of Jupiter will eclipse each other.
Comets, it is true, have somewhat less predictable orbits, but this is almost certainly because there is a boiling off of frozen ices as these objects approach the Sun, and a small rocket effect. The cometary incarnation of Venus, if it existed, might also have had such icy vaporization, but there is no way in which the rocket effect would have preferentially brought that comet into close passages with the Earth or Mars. Halley’s comet, which has probably been observed for two thousand years, remains on a highly eccentric orbit and has not been observed to show the slightest tendency toward circularization; yet it is almost as old as Velikovsky’s “comet.” It is extraordinarily unlikely that Velikovsky’s comet, had it ever existed, became the planet Venus.
SOME OTHER PROBLEMS
THE PRECEDING ten points are the major scientific flaws in Velikovsky’s argument, as nearly as I can determine. I have discussed earlier some of the difficulties with his approach to ancient writings. Let me here list a few of the miscellaneous other problems I have encountered in reading Worlds in Collision.
On page 280 the Martian moons Phobos and Deimos are imagined to have “snatched some of Mars’ atmosphere” and to thereby appear very bright. But it is immediately clear that the escape velocity on these objects—perhaps 20 miles per hour—is so small as to make them incapable of retaining even temporarily any atmosphere; close-up Viking photographs show no atmosphere and no frost patches; and they are among the darkest objects in the solar system.
Beginning on page 281, there is a comparison of the Biblical Book of Joel and a set of Vedic hymns describing “maruts.” Velikovsky believes that the “maruts” were a host of meteorites that preceded and followed Mars during its close approach to Earth, which he also believes is described in Joel. Velikovsky says (page 286): “Joel did not copy from the Vedas nor the Vedas from Joel.” Yet, on page