[trebb]

And the orbit will change just enough that, somewhere in its journey around the Sun, it will collide with another rock in space, that it would have missed if left alone, and one or the other (or both) will have their orbits altered to a rock-Earth meeting point.

Can't help but to be a bit ironic when we decide to "play".

[Paul R.]

And the orbit will change just enough that, somewhere in its journey around the Sun, it will collide with another rock in space, that it would have missed if left alone, and one or the other (or both) will have their orbits altered to a rock-Earth meeting point.

That is highly unlikely (I would guess on the order of millions to one against being hit by a sizeable altered-by-humans-in-this-manner orbit object, if not more, in the next 100 years or so) because space, even Solar System "space", is so big. Given more time the odds get worse (for Earth) but if by then we don't have VERY good detection and deflection tech, we DESERVE to be smacked!

Now, the chances of some human agency deliberately directing a sizeable object into the Earth, 50 to 1000 years down the road, are much higher, and the chances there will be a nuclear war on Earth, initiated by a 2nd tier power, that kills between a few million and a billion people, in the next 50-100 years, is around 1 in 2, IMO.