Yet, in our eagerness to reach for that first tentative foothold, we often falter and give way to gravity.

We find ourselves teetering, our balance gone. Then, when we finally achieve total balance, we discover we are now upright, balanced, and still standing. We have fallen, but not quite yet. That is how gravity works. We are a long time falling, and we will continue to fly for the next ten thousand years. The most surprising thing to scientists about gravity is that it is just so easy to understand. It was first proven by Isaac Newton, who postulated that if a body had a "sensible force" toward another body, then that body would have to be attracted to that force with an equal and opposite force.

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Newton realized that if he could be sure of the other body being there, then if the body he was trying to catch was on a hill, Newton could just run up that hill to catch it. So, he put a flagpole on a hill and the other body being examined was on the flag; the flag would remain upright. If he could be sure it was there, then if he wanted to catch that other body, he can just run up the hill, and then he will be sure the flag was up-hill. The first person to realize this was a very young man, who used his head instead of the hands to catch a rabbit.

The idea was first demonstrated by Newton's friend, Sir Isaac himself. A little more than two hundred years ago, in the nineteenth century, in one of his many experiments, Sir Isaac put a flag up on a hill, tried to catch a rabbit by running up the hill, and found that the rabbit had not taken the flag. That was when he figured out that running up a hill will not make the flag stay up. That, in fact, the flag on the hill would fall over, just as a body falls over when it is too impatient to wait for gravity to help its balance. And then, Newton realized, that when he runs up the hill, he will not even notice the flag. It will just be there. It will just have "sensible force" toward him. This is the kind of thing we really care about in life. In order to succeed in life, we have to have some idea just how things are going to work out. Science has come to understand that there is a force called gravity that lets us jump up but also lets us bounce back again.