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Retorts

Cometary Orbit

I attempt to answer P. Dalton [Retorts, August 1994].

The fragments of Comet Shoemaker-Levy 9 follow a band of similar orbits, mainly separated in time. In this respect they resemble a stream of water globules in a jet of water squirted from a hose or fountain (say).

Imagine a little paddle steamer on a fountain pond. The paddle wheel spins quickly so any paddle blade may be struck by each falling globule. But all globules strike the paddle steamer from the same angle of elevation.

Planet Jupiter spins once in about every 10 hours but all comet fragments impact at an angle corresponding to 6 degrees (18 minutes) behind the sunrise limb.

Changing course a bit. "Appearances notwithstanding, the multiple fragments of the comet are not travelling one behind the other. Rather, the line of fragments is oriented almost perpendicular to the direction of flight." (Astronomy, January 1994).

Imagine a dog (Jove) racing along a beach as a sweeping wave breaks a near distance offshore from the running dog. The extended wavefront (perpendicular to direction of flight), nevertheless breaks (impacts) successively at a similar site relative to Jupiter.

(Possibly gunshot from a discharging shotgun spread out in a cone of increasing diameter versus distance (time) from the muzzle. It is all a question of relative velocities?!.)

The large mass of Jupiter attracts the fragments and focuses the impact sites.

D.S. McDonald, Wellington