| > | Funny how you should take the *current state* of motion and
| > | extrapolate to be identical and constant over the last 10 years.
| >
| > I didn't know the Earth has slowed down or sped up appreciably
| > from 18.5 kilometers/second in the last 10 years. In FACT, I'm
| > sure it hasn't.
|
| Ah, and so even though the Earth and Cassini are both going in nearly
| circular ellipses (in fact several times in 10 years), the relative
| speed between Earth and Cassini is always 18.5 kilometers/second?

Relative speed, Phuckwit Duck?  Tut tut... you should be explaining that
to the local village idiot.
  "They are not speeds of objects or signals. They are merely
rates of change of distances between an object and signals."
  http://www.androcles01.pwp.blueyonder.co.uk/Dork/closingspeed.htm
Straighten his arse out, not mine. I know what a relative speed is, ah so.

 See also

https://home.deds.nl/~dvdm/dirk/Physics/Fumbles/ClosingSpeed.html