I understand how an orbit works, that the planets orbit the sun because they are in a constant ‘free-fall’ with the sun’s gravity.
Well you know how when they put satellites up they have to get them in an almost PERFECT orbit for them to work, (and even still most satellites will eventually deviate from their orbit anyway, many already have). Well why is it that all of the planets “just happen” to be in perfect orbit? I mean I can understand a fluke of nature getting a couple right, but we’re talking about 9 planets here!
Not sure I understand the question, really. Unless a piece of stuff either falls into the sun (not easy) or has enough kinetic energy to escape the sun’s gravity well it can be considered to be in some sort of orbit around the sun. (We ignore stuff too far away, and also things for which light pressure is an equal or dominant interaction with the sun.) There are the planets, with their narly circular orbits, bt there are astroids and comets with orbits that are eccentric ellipses. Anything coming in from far away from the solar system will probably enter and leave on a hyperbolic trajectory, unless there’s a big interaction that slows it down.
The planets are made of stuff hat conensed down at the same time as the sun, and the components were already in roughly circular orbits from the start. Anything hat wasn’t eventually got swept up by the large object that were – witness the impact craters on every body. But there’s still plenty of stuff going around in eccentric orbits that could eventually hit anther planet, like Comet Shoemacher-Levy. Or see any of a number of bad flicks about meteors striking the earth.
Orbits are not carefully laid out tracks in space which you must find and get on. If you throw a big lump of rock, it will enter some sort of orbit around the sun no matter how you throw it (Neglecting other planets for the moment here). However, you give the rock too much speed, the orbit will be “open” - that is, it will fly off into deep space. If the speed is low, the orbit will also be low, and if it’s too low, it may hit the surface of the sun. But the margin between these two speeds is enormous for planets.
Artificial satellites are a bit more tricky because many have very low orbits - barely high enough that it doesn’t hit the earth. In fact, it’s so low that there is a slight amount of air there, which can slow down the satellite over a period of years. When the satellite slows down, it falls to a lower orbit and hit even denser air, and quickly fall down to the ground. That’s why space stations need to be boosted to a higher orbit periodically. Still, it doesn’t need constant course correction; you just send up a Shuttle every few years and kick it into a higher orbit.
Some satellites need to be in a certain orbit to do its job. Weather satellites and communications satellites are obvious examples - they need control jets to make sure they don’t drift into the wrong orbit. Or sometimes, to go into another orbit as needed. And of course, manned spacecraft need course corrections to catch up with space stations or to get home.
Also, space stations may need constant attitude corrections, i.e. pointing. You have to keep the solar panels pointed at the sun. But that’s not an orbital correction.
i think i understand your question as asking how can a planet achieve something so difficult as an orbit but the mistake is to think an orbit is something very critical and that the planet or satelite would either fall to the sun or be launched into deep space if anything changed.
Imagine a body with a very elliptical orbit around the sun. It starts “falling” from aphelion gaining speed all the time until it reaches perihelion when it swings back and starts slowing down as it “climbs”.
Now suppose there is a force (friction, retrorocket, planetary attraction, whatever) that slows the body down. It will not “climb” up so far and the aphelion will be closer but the next perihelion will be at the same point.
If the planet continues to slow down, it will get to a point where aphelion and perihelion are at the same distance and the orbit is circular.
If it continues to slow down, the aphelion gets lower and after the whole orbit getting smaller and smaller, the planet finally crashes into the sun.
So you see there are infinite possible orbits, it is not so critical. It is only critical if you want your satelite to be right there.
Orbits are continually affected by exterior forces but that only means they change slightly.
First think of it as a sort of natural selection. Early in the solar system’s history, objects with non-circular orbits would tend to collide with other objects and be destroyed or absorbed into larger planetessimals.
Satellites in low Earth orbit experience drag with the atmosphere. The amount is tiny but it will eventually have an affect unless the orbit is periodically adjusted. Higher orbits, such as the geostationary (22,500 miles) experience less drag.
Planets experience drag as well, since they are always colliding with meteoroids and comets, but are massive enough that the loss of momentum is miniscule.
(1) The planets and sun formed out of a disk of material. The stuff accumulating in the “correct” orbits persisted, the rest did not.
(2) There used to be more planets, but they had non-stable orbits. The theory explaining the origin of the Moon is that a Mars-sized planet struck the Earth about 4 to 4.5 billion years ago. There were a lot of big collisions in the early solar system. Now, there are a lot of small collisions as most the big fragments have been used up.