Astronomer Tom Van Flandern (1940 - 2009) had a PhD in astronomy specializing in celestial mechanics. He was the former Chief of Celestial Mechanics at the US Naval Observatory. However, he left mainstream science when he began to believe that the conventional explanations for many of the phenomena of the solar system and the universe were incorrect. In particular, Dr. Van Flandern challenged the Big Bang Theory of origins, and the conventional explanation for the origin of comets and asteroids.
In his book Dark Matter, Missing Planets, and New Comets: Paradoxes Resolved, Origins Illuminated (1993), Dr. Van Flandern lays out the problems with the conventional explanations for the topics mentioned above, and puts forward his controversial alternative theories. While I personally believe that the hydroplate theory of Dr. Walt Brown provides a better explanation for the origin of comets and asteroids, and one that is backed up by extensive corroborating geological evidence here on earth (see list and links in this post), it is important to note that Dr. Van Flandern was alert to the massive problems in the conventional theories and was bravely putting forward alternative views, even though it made him unpopular among his fellow astronomers.
In a similar way, I believe that the sheer volume of alternative theories for mankind's ancient past is the result of the massive problems with the conventional timeline, which stimulates thinking people to explore other possible explanations. Even though we might not agree with all or any of them in their entirety, we should view these theories as evidence of the problem with the accepted view, and commend those who are willing to risk ridicule in order to put forward a better suggestion.
Dr. Van Flandern noticed the harmonic relationship of the orbits of the existing planets and the well-known fact that there is a gap in the pattern between Mars and Jupiter, and became the leading modern proponent of the Exploded Planet theory, which proposes that there was once a watery "Planet V" between Mars and Jupiter, which exploded, leaving the asteroid belt in its wake. He further controversially suggested that the inhabitants of this exploded planet, realizing in advance the need to leave, came to earth and that we are their descendents.
Whatever one thinks of these speculations of extraterrestrial life, Dr. Van Flandern's arguments about the problems with the conventional explanation for the origin of comets are sound, and his proposition that comets originated with a violent explosive ejection from the inner solar system appears to provide a much better answer than the existence of a hypothetical Oort Cloud.
In the previous post about Comet Hale-Bopp, we examined some of the problems with the conventional explanations for the origin of comets. In his book, which can be read online here, Dr. Van Flandern explains the conventional theory and its problems. First, he explains the size of the proposed Oort Cloud, which is important to understand in order to perceive the problems with the theory. If the entire solar system as we know it, out to the orbit of Pluto, were the size of a US dime (just over one centimeter), then the Oort Cloud would be a shell of comets in a generally stationary posture, hovering far from the sun, an average of six meters away (over nineteen and a half feet out). This analogy reduces the actual distances by a factor of 1015 and can help us understand how hard it would be for a comet, hovering in stasis, to be dislodged in such a way that it would actually enter the dime-sized solar system and be visible to us on earth at all.
Dr. Van Flandern explains:
These comets [in the hypothetical Oort Cloud] are essentially stationary with respect to the Sun, having mean velocities in the scale model of just 3 millimeters per 1000 years. Passing stars, on the other hand, move relatively rapidly, with typical speeds of a meter or so per 1000 years, and stir up the comets they come very close to. It is deduced that in this way an occasional comet will by chance have its motion redirected towards the Sun in such a way that it will manage to pass within the 1mm-diameter sphere centered on the Sun, within which we on Earth can discover and observe it. [. . .] The number of comets within the cloud is believed to be immense in order to provide the few comets we observe, because the chances are so small of any one comet being perturbed into the observable range. And the absence of certain planetary perturbations in their motion proves that a large number of new comets arriving from the cloud could never have passed so close to the Sun before, even though they complete a revolution around their orbits every few million years. How could these curious objects evolve into such a seemingly improbable situation? 181.Dr. Van Flandern then goes on to illustrate evidence which argues against the Oort Cloud theory. For one thing, it is difficult to explain a mechanism that would allow comets to coagulate at all in the near-perfect vacuum that exists so far from the sun. Further, the Oort Cloud theory must account for the complete regeneration of the cloud whenever it is wiped out by galactic tides, molecular clouds, and passing stars.
A major problem he and other astronomers have also pointed out is the complete absence of hyperbolic comets -- comets whose orbits are so fast that they will come into the solar system only once, slingshot around the sun, and then disappear into deep space forever, never to return. If comets are launched from an Oort Cloud by the perturbation of passing stars, some should travel so fast that they would have hyperbolic orbits. However, none with such velocity have ever been observed. On the other hand, if comets originated from an explosion in the inner solar system, then any matter that was not initially traveling fast enough to completely escape the sun's pull would eventually reach a point where it came back: such objects would then orbit far out again and return. In other words, if comets came from the inner solar system originally, we would not expect to see hyperbolic comets, only comets making their first return or later returns after such an event.
As explained in the previous post, over millions of years, some of these non-hyperbolic comets might be accelerated by a close encounter with Jupiter to the point that they would be ejected from the solar system, and this is the reason that explanations for comet origins must be fairly recent, because if comets originated billions of years ago, Jupiter would have captured or ejected more of them than exist today. This is why there is an Oort Cloud theory in the first place, but if comets originated in a relatively recent violent explosion from within the inner solar system, it would also explain the number of comets still in existence. However, the lack of hyperbolic comets shows that the Oort Cloud explanation is not a good one, and that an explanation which provides for comet origins from the inner solar system would be far more satisfactory.
Incidentally, Dr. Van Flandern points out that his criticism of the Oort Cloud theory does not imply criticism of the cloud's namesake in any way. In a footnote on page 191, Dr. Van Flandern says "Astronomer Oort always maintained that an origin of comets from within the solar system, perhaps in connection with the event which gave rise to the asteroid belt, was the most probable."
While Dr. Van Flandern proposed an exploding fifth planet for their origin (a planet which must have been watery, since comets are mostly ice), the hydroplate theory of Dr. Walt Brown would also provide the same satisfactory explanation as the theory of Dr. Van Flandern. The only difference is that the violent explosion that launched the comets and asteroids came from earth rather than a hypothetical planet between Mars and Jupiter, and that there is extensive evidence for such an explosion -- which initiated a global flood -- in the geological record on earth's surface including on the bottom of the oceans.
It is also worth pointing out that the Exploding Planet theory of Dr. Van Flandern has been used as a launching point for the idea that our solar system was the scene of an ancient extraterrestrial war, a war in which the destruction of the missing planet was the ultimate blow. This theory, which has been put forward by Dr. Joseph P. Farrell in his books including the Cosmic War, also falls into the category of theories written by those who perceive the enormous problems with the conventional academic models and which try to explain the ancient history of mankind on earth in a way that is more consistent with the evidence. Whether or not we actually agree with the hypotheses that alternative theorists put forward, I believe they should be commended for bravely offering alternatives to the accepted wisdom.
Tom Van Flandern's book provides an excellent explanation of the problems with the currently-held theory of comet origins. It is clear from his own theories and of others who have followed his work that the question of comet origins actually intersects the question of ancient human history on earth as well. I personally believe that the hydroplate theory offers a new and very helpful perspective on these questions, not only the question of the origin of comets but also of the mysteries of mankind's ancient past. The Mathisen Corollary book explores these connections.