The Faint Young Sun Paradox and Its Solution

Sagan and Mullen proposed that the Sun's luminosity (energy flux) was probably low enough to freeze the oceans some 2 billion years ago if the atmospheric composition were the same as now (the 'faint young Sun paradox'), yet for the last 3.8, possibly even the last 4.4, billion years the Earth has had liquid oceans, a fact established from the fossil and marine sedimentary record and the isotopic record of Hadean zircons. The solution to this paradox is that atmospheric compositions have not been constant over geologic time; rather, higher levels of the greenhouse gases carbon dioxide and likely methane were present in the past, especially the Early Precambrian, to generate warming compensating the fainter Sun, even overcompensating, generating higher temperatures than at present.

10 Ways To Fight Off Cancer

10 Ways To Fight Off Cancer

Learning About 10 Ways Fight Off Cancer Can Have Amazing Benefits For Your Life The Best Tips On How To Keep This Killer At Bay Discovering that you or a loved one has cancer can be utterly terrifying. All the same, once you comprehend the causes of cancer and learn how to reverse those causes, you or your loved one may have more than a fighting chance of beating out cancer.

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