The faint young sun paradox contradicts an old earth (Talk.Origins)
- According to standard models of the sun, the sun's luminosity has increased by 40 percent since the origin of the earth (the "faint young sun paradox"). This would mean that the early earth could not have supported life. Thus an old earth is impossible; the earth must be young.
Source: Faulkner, Danny, 1998. The young faint sun paradox and the age of the solar system. Impact 300,
CreationWiki response: (Talk.Origins quotes in blue)
1. The change in luminosity is not as drastic as it sounds. Much of the change would have occurred before the origin of life; the luminosity increase since the origin of life is about 25 percent. And this translates to a 7 percent increase in temperature when the earth's heat outflow is taken into account.
First of all, the Earth's average temperature is about 15 degrees C or 258 K. Now 7 percent of 258 K gives an increase of 18 degrees, from -3 degrees C, which is below freezing. This would be a problem for the orgin of life, which has enough problems without such low temperatures.
2. The 7 percent change described above assumes no feedback system, but the earth's climate feedback systems are complex. In particular, the greenhouse effect and albedo could moderate the temperature further. On the early earth, it is likely that greenhouse gases such as carbon dioxide and methane were commoner than they are today.
The problem here is that this would require a very delicate and improbable balance. If the greenhouse effect did not decrease fast enough the result would be a runaway Venus-like greenhouse effect. If it decreased too quickly the Earth would have frozen over.
3. Life has survived fairly large changes in climate over its history, from a near-global glaciation in the late Precambrian, to a global temperature warmer than today's in the Carboniferous.
But the problem here deals with the origin of life, not its ability to adapt to changes.