One of the cooler things about the Oort Cloud is that it may not even exist.
It is purely theoretical, and has never been directly observed. The reason for its theoretical existence is because it explains the behavior of comets. Comets seemingly come out of nowhere, and while most of the rest of the solar system stays within the plane of the solar system (except for that contrarian former planet Pluto and the odd asteroid here and there), comets come barreling in at all possible angles.
So there's that.
Also, if comets were simply orbiting elements of the solar system, zooming toward the sun every few hundred years or so, there wouldn't be any more comets. The solar system has been around a very long time, and comet orbits are by nature pretty unstable; after this long a time most comets should have collided with a planet or the sun, or been flung out of the solar system by gravity, or simply broken apart by close passes to the sun.
And the Oort Cloud explains that pretty well too.
Here's the theory: there is a great cloud of icy rocks surrounding the solar system in a sphere (as opposed to a disc), rocks left over from the birth of the solar system. The outer edge of the cloud is VERY far away, around a light year (the closest star, by comparison, is about 4 light years away). Since these iceballs are so far away, they are only tenuously connected by gravity to the sun, and thus are easily pulled out of orbit by passing stars, passing black holes, the plane of the galaxy, etc.. When something passes by, it affects the orbits of what it encounters. If that something is large enough, and passes close enough, everything in the Oort Cloud goes a little nutty. Orbits near the cosmic interloper change, and there is a cascade effect where objects with changed orbits change the orbits of other objects, which in turn affect other orbits, which in turn affect other orbits, on and on.
The result is the the solar system gets pelted with iceballs, like pellets shot out of a shotgun. Which helps explain all those craters on the various moons and planets out there. And helps explain as well why there is a mass extinction event here on Earth every several million years (tangentially related is the idea that every time we pass through the plane of the galaxy, roughly every 32 million years, the Oort Cloud gets jostled and everything dies; the fossil evidence bears this out).
It's also an explanation for those uncommonly beautiful objects occasionally gracing our skies, improbable tails arching across the sky like a bridge to a foreign land.
Comets might even explain the existence of life itself. They contain a lot of water, and are widely theorized to contain the amino acids responsible for life as well. So comets may have brought life came to Earth, and perhaps others places as well.
So. Let's recap. It might or might not exist. It had been around since the beginning of the world. It explains the physical world around us. It graces us with uncommon beauty. It is responsible for mass extinctions, and perhaps for the origin of life as well.
Might exist, might not. Timeless and beautiful. Responsible for the life and death of worlds.
Remind you of anyone?