Faint Young Sun Paradox Resolved
Written by Professor Claes Johnson
The faint young Sun paradox describes the apparent contradiction between observations of liquid water early in the Earth’s history and the astrophysical expectation that the Sun‘s output would be only 70% as intense during that epoch as it is during the modern epoch. The issue was raised by astronomers Carl Sagan and George Mullen in 1972.
The argument supports the idea of the thermodynamics of the atmosphere as an air conditioner acting to reduce the lapse rate and thus cool the Earth surface as the inside, with the the tropopause as the outside with a temperature set by the input via Stefan-Boltzmann.
PS Several unsuccessful attempts to resolve the paradox have been presented recently:
- Faint Young Sun Paradox remains (Nature June 2011)
- Why early Earth was no snowball (Potsdam Institute Dec 2012)
- Hypothesis for Faint Young Sun Paradox (Purdue Univ May 2012)
- Faint Young Sun Paradox not resolved (NASA May 2012)
- Paradox: Is there even life on Earth (Smithsonian Astrophysical Observatory Sept 2012)
- Faint Young Sun Problem (Geophysical Research Letters 2012).
- Early Earth Atmosphere: Right mix of greenhouse gases (Nathan Sheldon)
- Geology: Much more geothermal energy
- Biology: Life developed on a cold planet (John Priscu)
- Fundamental Physics: e.g., gravitational constant has varied
- Astrophysical Solutions: Young Sun was not faint.
Read more at claesjohnson.blogspot.co.uk