Earth, Venus, and the Moon may all be victims of ancient hit-and-run planetary collisions

A big problem with trying to figure out how the planets formed is that it happened 4.55 billion years ago. The record’s a little blurry by now.

We have a lot of science and understanding of the planet-building processes, and can model them on computers by solving the various equations involved. But these models are only as good as the math and physics that go into them. If there’s some process involved we don’t know about, then the models that don’t include it could very well be wrong.

This ha...