Yes. Some years ago a computer was developed called the 'Digital Orrery' to calculate the orbit of Pluto for the next 40 million years at 40 day intervals. This is enough time for Pluto to complete 15,000 orbits of the Sun. What the astronomers found, and what is shown in the above figure, was that the orbit of Pluto is chaotic, which means that its long-term shape depends very sensitively on the exact input parameters used to start the calculations. It is not a smooth ellipse like the other planets seem to be.Not knowing, today, where Pluto is to a precision of less than one kilometer adds up over thousands of orbits to make the predictions vary over a wide range of possibilities. They were able, however, to show that for many reasonable choices of input parameters, Pluto will never get closer than 100 million miles of Neptune because Pluto and Neptune are apparently locked into a resonant condition between the orbital periods of the two planets.
More recently in ca 1999, astronomers using a similar computational scheme found that the orbits of Mercury, Venus, Earth and Mars are not as stable as they seem over the long term...say a few billion years or longer. Depending on the exact initial conditions, the cumulative influences of Jupiter and Saturn eventually cause the inner planets to have more elliptical orbits, and in some simulations, Earth, Mars or Venus are actually ejected from the solar system! You can be sure that as computing techniques and the quality of the data improve, more of these studies will be carried out, but the quality of data needed because of the build-up of 'roundoff error' in the calculations, is terribly exacting! You would need to know planetary masses and current speeds and locations to many more decimal places than they are today!
A good introduction to solar system chaos theory can be found at J. Wisdom's pages at MIT on an Introduction to Chaos in the Solar System.
Copyright 1997 Dr. Sten Odenwald
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