Abstract
There is a set of terrestrial planets that we can study much closer to home. They are separated from us not by space but by time. Our planet has been around for 4.6 billion years, about a third of the total age of the Universe (13.7 billion years). Throughout its long life, it has changed so much that, were we to be transported to one of its past incarnations, it would appear as alien as an exoplanet.
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Accidents may happen to shorten this lifetime, such as a very close encounter with another star that perturbs the orbits in the Solar System, but such encounters are extremely rare because the space between the stars is so vast. There is also the small possibility of the orbit of Mercury becoming unstable, see page 107.
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At the distance of the Earth, the temperature at which heat loss by infrared radiation and heat gain by sunlight balance each other is around zero degrees Celsius.
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With possible exceptions. The first, of course, is when one animal species starts burning fossil fuel and putting carbon buried underground back in the atmosphere. Another one is weirder: recent research suggests that a large part of the marine carbonate rock deposits, such as the White Cliffs of Dover, may result from carbonates precipitated in the guts of fish. Therefore ocean fish may play a part in the carbon-rock cycle and help remove the CO2 out of the atmosphere.
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© 2014 Springer Science+Business Media New York
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Pont, F.J. (2014). Back to Earth. In: Alien Skies. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-8554-4_8
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DOI: https://doi.org/10.1007/978-1-4614-8554-4_8
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