When The Planet Spun 10 Times Faster

A cataclysmic collision not only created Earth’s moon, but may have also knocked Earth over on its side. In a paper published by the journal Nature, scientists say their numerical simulations indicate that the collision of a Mars size object with the early Earth left our planet tilted at an angle of 60 to 80 degrees and spinning rapidly, once every 2.5 hours, almost 10 times as fast as today. But the simulations also show how the dynamics of the moon and Earth slowed down over the next four billion years of the solar system. For the first time, this paper has a model that says researcher can start in one place; explain all of that without invoking any other follow-on event. “Where did the moon come from?” has been a persistent question over the eons. Among the rocky planets of the inner solar system, Earth is an anomaly. Mercury and Venus have no moons at all, and Mars only has a couple of tiny moons that may be captured asteroids. Earth’s moon, by comparison, is a giant, more than 2,000 miles in diameter. Recently the preferred explanation for the origin of the moon has been “the big whack”: soon after the formation of the solar system, the Mars-size interloper that astronomers have named Theia bumped into Earth. The resulting slosh of debris coalesced into a slightly larger Earth and the moon in orbit around the Earth.