The moon may have stopped the early Earth from being a frozen snowball

By Jonathan O’Callaghan

The young Earth and moon

MARK GARLICK / SCIENCE PHOTO LIBRARY

The sun is thought to have once been far fainter than it is today, which should have left Earth frozen as a global snowball. That it wasn’t, a discrepancy known as the faint young sun paradox, has long plagued astronomers, but now we might have an answer: the moon helped keep Earth warm.

Models of the sun’s past suggest it was up to 70 per cent dimmer in its first 100 million years. “The surface of the Earth should have been frozen for at least a billion or …