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on one side, namely, more or less towards the centre of the bunch. Some stars would pull it rather to one side of the centre, others rather to the other side: but there would be no stars at all to pull it away from the centre, "and hence it would know very definitely in which direction to move, namely towards the centre. Let us go with it in its journey and see what happens. After a little time it would be no longer quite on the boundary, but would have penetrated a little way into the bunch. There would now be a few stars pulling it away from the centre, but only very few compared with those urging it on; it would still be urged centrewards and would quicken its pace: and without troubling about the details you will see that this sort of thing would go on until the star arrived at the centre, when there would be no force on it either way, as we said before. But that does not mean that it would stop, for it has got "way on." Let us look for a moment at this pendulum. When I let it hang vertically it is like a star at rest in the middle of the bunch; there is nothing to make it move. But if I pull it to one side it is like our star on the outside of the bunch—it is being pulled towards the centre, and if I let it go it swings thither. But on arriving at the centre it does not stop, because, although there is no force moving it forwards, it has got "way on" and so passes through. Directly it has passed through, the force begins to call it back, but it cannot stop it all at once—the pendulum swings out to the other side before returning. So with our star which we started from the outside of the bunch or cluster: it will arrive at the centre,