Early Solar Output
Early in the Earth's history, the Sun's output would have been only 70% as intense as it is during the modern epoch. In the then current environmental conditions, this solar output would have been insufficient to maintain a liquid ocean. Astronomers Carl Sagan and George Mullen pointed out in 1972 that this is contrary to the geological and paleontological evidence.
According to the Standard Solar Model, stars similar to the Sun should gradually brighten over their main sequence lifetime. However, with the predicted solar luminosity 4 billion (4 × 109) years ago and with greenhouse gas concentrations the same as are current for the modern Earth, any liquid water exposed to the surface would freeze. However, the geological record shows a continually relatively warm surface in the full early temperature record of the Earth, with the exception of a cold phase, the Huronian glaciation, about 2.4 to 2.1 billion years ago. Water-related sediments have been found that date to as early as 3.8 billion years ago. Hints of early life forms have been dated from as early as 3.5 billion years, and the basic carbon isotopy is very much in line with what is found today. A regular alternation between ice ages and warm periods is only to be found occurring in the period since one billion years ago.
Read more about this topic: Faint Young Sun Paradox
Famous quotes containing the words early, solar and/or output:
“Our bad neighbor makes us early stirrers,
Which is both healthful and good husbandry.”
—William Shakespeare (1564–1616)
“The solar system has no anxiety about its reputation, and the credit of truth and honesty is as safe; nor have I any fear that a skeptical bias can be given by leaning hard on the sides of fate, of practical power, or of trade, which the doctrine of Faith cannot down-weigh.”
—Ralph Waldo Emerson (1803–1882)
“Lizzie Borden took an axe
And gave her mother forty whacks;
When she saw what she had done,
She gave her father forty-one.”
—Anonymous. Late 19th century ballad.
The quatrain refers to the famous case of Lizzie Borden, tried for the murder of her father and stepmother on Aug. 4, 1892, in Fall River, Massachusetts. Though she was found innocent, there were many who contested the verdict, occasioning a prodigious output of articles and books, including, most recently, Frank Spiering’s Lizzie (1985)