What would have happened on Earth if, about 4.5 billion years ago, Theia had passed peacefully on its way without striking Earth and forming a moon ?
Well, life of some sort would probably exist on Earth, but humans almost certainly wouldn’t. Think of the very long course of evolution, the small changes, the minute adaptations that organisms make to their environment. It would only have taken small changes to Earth’s environment to have dramatically altered the course of evolution. I wouldn’t be writing this article – and you wouldn’t be reading it.
And if the Moon had never formed, Earth would be a very, very different place. An Earth day would be only 8-10 h long, with no moon to slow it down. The faster rotation would cause winds of 160-200 km to sweep Earth’s surface. The tilt axis of Earth would wobble, resulting in dramatic changes in temperature over thousands to millions of years. And although our seas would still be tidal, the tides would be much smaller – caused only by the Sun.
What kinds of life might have evolved on moonless Earth, capable of withstanding extreme temperatures, high winds, small tides and short days ?
By Erin Tranfield