Tag Archives: giant impact hypothesis

01. Orbis Tertius | 5. The horizon of our concerns | d. Your uncertain disk i.

i. On the morning of our departure for Rye, we heard on the radio of new evidence emerging in support of the “giant impact hypothesis”, an idea that attempts to explain the creation of the Earth’s moon as the result of a collision between our planet and Theia¹ — a smaller, Mars-size planet — four and a half billion years ago. The idea had long been considered problematic due to the similarities between the chemical makeup of Earth and its moon: were it formed from the remnants of another planet, there would be a difference. Recent studies of oxygen isotopes in moon rock however, had found significant-enough differences to elevate the “giant impact hypothesis” to a new level of plausibility.

Giant impact


¹ Theia, the Titanic mother of Selene (the moon) was goddess of — among other things ­— glitter.