He also gives an average period for a class of short-period comets of 7 years, yielding an average lifetime of around 500 years.With the average number of this class which are visible any one time, a 4.5 billion year old universe requires that at least several hundred million coments existing away from the sun have been diverted into the solar system.A couple of notes: for most of the arguments, I provide a background in case you or someone who reads the record is not familiar with the subject area.
These methods don't assign an exact age; the rates and initial conditions are not exactly known.
However, since the "young" and "old" age ranges differ by 5 1/2 orders of magnitude, it is easy to say which pieces of evidence favor which theory.
Paul Joss, in the above cited reference, calculates "no," by a factor of 40,000. H Delsemme ("Origin of Short-Period Comets," Astronomy and Astrophysics, 7-381, December, 1973) calculates that the answer is "yes." Edger Everhart (University of Denver), who has reviewed both calulations and has contributed his own theories ("Evaluation of Long- and Short-periord Orbits," Comets, edited by Laurel L.
Wilkening, University of Arizona Press, 1982), the answer is unknown.
Paul Joss, of the Institute for Advanced Study in Princeton, NJ, gives a value of 70 as an average.