Why the Moon's New Birthday Means the Earth Is Older Than We Thought 98
Daniel_Stuckey (2647775) writes You're likely familiar with the theory of how the Moon formed: a stray body smashed into our young Earth, heating the planet and flinging debris into its orbit. That debris coalesced and formed the Moon. The impact theory still holds, but a team of geochemists from the University of Lorraine in Nancy, France has refined the date, finding that the Moon is about 60 million years older than we thought. As it turns out, that also means the Earth is 60 million years older than previously thought, which is a particularly cool finding considering just how hard it is to estimate the age of our planet.
Re:Age of the earth (Score:5, Interesting)
apparently they're counting from the formation of the solar system, for which they don't have a year. previously had thought the earth to have formed 100 million years after that event but now they put it at 40.
Re:Age of the earth (Score:5, Interesting)
With what did the collision happen if the earth wasn't already there? I fail to see how the moon being carved out the earth 60 Myr earlier affects the age of the earth.
I believe that conclusion comes from the idea that the collision was between two proto-planets - that is, for all intents and purposes, the Earth and the Moon only came into being after the collision. Wikipedia calls them "the proto-Earth" and "the impactor" which supposedly was the size of Mars. An impact like that would have changed everything so dramatically that even if we had some age-measurable material that survived the impact, we wouldn't know whether it came from the proto-Earth or the impactor. So it makes some sense to use that event as the "birth" of our planet.
And of course you can't just use the absolute age of some atoms, if we could measure such a thing. Maybe some of the heavier atoms fused in that impact, but some material came the supernova(e) that seeded our solar nebula with heavier atoms and induced the rotation that eventually became the Sun's accretion disk, some came from other, smaller impacts of bodies probably formed at the beginning of the Solar System, etc.