Known as the giant-impact hypothesis, this proposed event involves a collision between Earth and a hypothetical Mars-sized protoplanet astronomers call Theia. (Image credit: Mark Garlick/Science Photo Library/Getty Images)

For as long as humans have watched the night sky, we have wondered about the moon , pondering everything from its alien appearance to its influence over phenomena on Earth such as ocean tides, climate stability, and even the natural rhythms of many organisms.

Among the many questions we have about Earth's lone natural satellite, one remains preeminent: what are the moon's origins , and how long has it orbited Earth?

Today, the leading theory among astronomers is that deep in our planet's past — perhaps within roughly the first 100 million years of solar system history — Earth collided with a planet-sized object, creating the moon within a period that may have been as short as just a few hours .…