No. 120: Nov-Dec 1998
During the 1950s, the campaign of mainstream science to discredit Velikovsky assured the public that the solar system was the epitome of stability -- wayward planets were impossible. Then along came chaos theory which implied that the flight of a butterfly in Brazil could, in principle, affect weather in Canada. In effect, a slight change in initial conditions could, in the fullness of time, have very large effects. Now, it is generally admitted that the solar system is chaotic after all. Each planet is subject to the tiny, butterfly-like gravitational tugs of the other planets, especially Jupiter. Given enough time, these gravitational nuances can result in the ejection of a planet from the solar system -- and may already have done so in the past!
Mercury and Mars are the most vulnerable on a billion-year time scale. In the case of Mercury, its orbit will become more and more elliptical according to computer simulations. Eventually a close gravitational encounter with Venus is possible. This could send Mercury careening off into deep space. The probability of this happening is only 1 in a 1000 over 5 billion years, but it is not zero.
Mars might likewise be ejected by a passing nudge from earth. However, this encounter could go the other way. Depending upon the celestial dynamics of the encounter, Mars might gravitationally fling earth out into the Galaxy, and our planet would truly become "Spaceship Earth."
(Frank, Adam; "Crack in the Clockwork," Astronomy, 26:54, May 1998.)
Comment. The computer simulations used in the foregoing study have to assume that we know all the forces acting in the solar system. This may not be the case according to the next item.