The anthropic principle — which argues that our universe is finely tuned to support life and there is no point in asking why it is so — has been criticised as lazy, untestable science. Now there may be a way to test the theory for one of the most problematic instances of fine-tuning.

Cosmologists have observed that the expansion of the universe is accelerating, and have attributed this to an inherent energy of space-time described by the so-called cosmological constant (CC). Quantum physics predicts that the CC should be more than 10^120 times larger than observed — a value so large it would blow the universe apart before stars or galaxies formed — yet instead it seems to be just right for the formation of giant galaxies such as our Milky Way, and hence for life.

This led Nobel laureate physicist Steven Weinberg to propose in 1987 an anthropic explanation … (subscription required)