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The major members of our Solar System have been described previously as rather solitary and antisocial beings. Each planet stays on its nearly circular orbit as it revolves around the Sun. Except when the wildly eccentric Pluto crosses over Neptune's path, no planet invades its adjoining neighbor's territory. The planets are like a row of suburban homes separated from one another by a low but wide hedge; while there is no real privacy from curious snooping at least nobody can directly walk into your backyard.
For better or worse, there are plenty of things able to jump over the hedge and barge into the Earth’s backyard. Our planet is not in an exclusive area. Some of the visitors from space merely glide pass the Earth, others crash into its atmosphere. You are probably already acquainted with one group of visitors. On a clear, dark night, an occasional bright line will flash across part of the sky. These flashes are particles of dust burning up in the Earth’s atmosphere.
This chapter will be devoted to the errant children of the Solar System. The eccentrics who have no respect for even the ecliptic and seem to wander wherever they please. Do they really? Do these small and troublesome object defy both Kepler and Newton? Not really. Any object captured by the Sun's gravitational field is forced to revolve around it according to the same rules applying to the planets. It is just that these rules provide much greater latitude than those taken by the planets. First of all, there is no law restricting an object to the ecliptic. Both Mercury and Pluto have a high inclination from the plane of the Solar System. Other smaller objects have an even greater inclination and pass through the Solar System's plane at a right angle as they orbit around the Sun, or travel in the opposite direction from the planets.
Eccentricity measures the deviancy of an orbit from a perfect circle. All the planets are at least a bit eccentric. Every eccentric orbit around the Sun has a point where it's closest to the Sun and a point where it's farthest. For objects with extremely eccentric orbits, the difference between their minimum and maximum distances from the Sun is enormous. An object may be billions of miles away from the Sun at one time and then, half an orbit later, almost graze it. Even though most of the matter of the Solar System is concentrated along the ecliptic so that the picture of the Solar System as a giant phonograph record is more or less a valid one, keep in mind that there are exceptions. And these exceptions may cross over the orbits of the outer planets and approach the Earth.
... Now we know
The sharply veering ways of comets, once
A source of dread, nor longer do we quail
Beneath appearances of bearded stars.
Edmund Halley (1656-1742)
It's five miles wide ... It's coming at 30,000 m.p.h ... and there's no
place on Earth to hide! METEOR.
from 1979 movie publicity poster