Originally published: Jun 26 2014 - 1:30pm, Inside Science News Service
By: Ker Than, Contributor
(Inside Science) -- Terrestrial animals may owe a special debt to the sun and the moon. It may have been their combined pull on ancient Earth's oceans that helped primitive air-breathing fish gain a toehold on land, new research suggests.
In a new study, published in the journal Proceedings of the Royal Society A, physicist Steven Balbus argues that the gravitational forces generated by the sun and moon would have been conducive to the formation of a vast network of isolated tidal pools during the Devonian Period, between 420 to 360 million years ago, when fish-like vertebrates first clambered out of the sea.
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“By the end of the Devonian, there were vertebrates that were quite at home moving around on land,” said Balbus, who is at the University of Oxford in the United Kingdom.
According to Balbus, a rather remarkable confluence of cosmic, geological and biological events occurred during the Devonian period that helped jump-start life on land. First, when viewed from the Earth, the sun and the moon appeared to be almost the same size, as is true today. This is called having the same angular diameter.
“The sun is much bigger than the moon, but it’s also much farther away, so the two bodies look to be about the same size to us. This is extraordinary,” Balbus said. He added that it's very unusual for an Earth-sized planet to have such a large moon.
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