Why doesn't the earth fall out of orbit into the sun, just as earth satellites eventually do?

I understand the basic mechanics of orbiting bodies -- they are actually 'falling' around the orbited object. What I don't understand is how the balance could be so perfect that even over billions of years, the earth stays in place. And many meteors and meteorites hit the earth all the time. ... show more I understand the basic mechanics of orbiting bodies -- they are actually 'falling' around the orbited object. What I don't understand is how the balance could be so perfect that even over billions of years, the earth stays in place. And many meteors and meteorites hit the earth all the time. Wouldn't these impacts eventually alter the orbit enough to doom the earth?
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