Swimming Upstream

I photographed trout in the Truckee River, the only river that empties into Lake Tahoe. Our form of life depends upon liquid water, which makes up 70% of human bodies. Liquid water only exists at temperatures above 273 degrees Kelvin, and Earth's average temperature is about 283K. We occupy a very narrow temperature range.

According to the Standard Solar Model, life as we know it could not have evolved here because when Earth was formed the Sun was only about 75% as luminous. Power is related to temperature by the Sefann-Boltzmann Law P = aT^4. Earth's temperature would have been (.75)^{1/4} or 93% of its present value. At a temperature of -10 C Earth would have been frozen solid, making evolution of life unlikely. Fortunately the Sun turns its fuel to energy according to E = mc^2. Speed of light c has changed in exactly the amounts needed to keep the Sun constant.

The first Earth life was probably bacteria living below the surface. Sea life evolved next, and was confined the water for much of Earth's history. The trout must think it amazing that we survive above the surface, and would drown in water. We are one step in an evolution where the next stop is Space.