A Mug friend mentioned two things I'd never even heard about. OORT CLOUD and KUIPER BELT. Know what they are?

The more they find, the  more wonderful it is.

Calculating orbits is a lot simpler than we might think. It might be beyond my mathematical skill but the laws governing them have been known for nearly 400 years. The more difficult part is making the necessary measurements from observations. The planetary laws of motion were established by the German astronomer Johannes Kepler as far back as the 17C. This is one of his remarks:

"I demonstrate by means of philosophy that the earth is round, and is
inhabited on all sides; that it is insignificantly small, and is borne
through the stars."

(The study of nature was called "philosophy" then. The word "science" was not yet invented.) I wonder what Kepler would say if he could come back now and see that recent photo a NASA probe took from somewhere far out in the Solar System, looking back towards the Sun. It was just an engineering test but the NASA staff published it because they were so startled and impressed by what it shows - they realised one tiny, bright dot against the star-studded blackness is the Earth, far away in the distance.

It's not so much that comets come from the Kuiper Belt as that their orbits' further limits are in it. They are small, and their orbits around the Sun are huge, very elongated ellipses so they spend most of their time too far away to be visible to us. Also as they recede from the Sun they become colder, losing their tails of ice evaporated by the Sun's warmth, making the lonely little things even less visible.  
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