giant impact theory

American  

noun

1. a theory suggesting that the Moon was formed when Earth collided with a Mars-sized body about 4.5 billion years ago, ejecting rocky material into space that later formed the Moon.

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giant impact theory Scientific  

/ jī′ənt /

1. A theory that explains the origins of Earth's moon, postulating that an asteroid roughly the size of Mars impacted the Earth during its formation. This impact resulted in rocky surface material being blown outward from the Earth, some of which accreted to form the Moon. This theory explains the similar oxygen isotope ratios between the Earth and the Moon as well as the Moon's lack of an iron core. It also accounts for the angular momentum that was necessary for the Moon to reach its current position.

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Example Sentences

What’s more, not only is the chemistry of the giant impact theory flawed, but also so is the physics.

From Time • Jan. 11, 2017

One stumbling block of the giant impact theory of moon formation has been the incredible isotopic similarities between the Earth and the moon.

From Scientific American • Oct. 17, 2013