Terminal lunar cataclysm

The stability of our solar system is an illusion of our short time span looking at it, and Newtonian Clockwork physics.  There has been a lot of movement.

At one point Jupiter comes in close enough to the Sun to seriously mess up Mars.  Earth would have been toast, but it did not exist yet.

There is the potential for further movement.

The Madness of the Planets
Corey S. Powell, Nautilus, 12 December 2013 (hat tip: NC)

So are we home free? No again. “The terrestrial planets, they are not totally stable,” Morbidelli says. That instantly captures my attention: Earth is one of the four terrestrial planets. “Mercury is on the edge of the instability, and it could go nuts, start to encounter Venus, then the orbits of Venus and the Earth could become unstable themselves.” From there, Venus could collide with Earth, or Earth could go careening off on a totally new orbit, sterilizing the planet. The odds are not great, but they’re not all that small either—about 1 percent over the next few billion years.

I have been re-reading Lucifer's Hammer, so this is all of interest to me.