Certainly -- our sun will eventually radiate away all its useful energy and that energy, although not lost, will assume a form that can no longer be exploited.

Certainly -- our sun will eventually radiate away all its useful energy and that energy, although not lost, will assume a form that can no longer be exploited. This shows the truth of the expression "entropy increases over time". Reference: http://en.wikipedia.org/wiki/Entropy_(arrow_of_time) http://en.wikipedia.org/wiki/Entropy_(arrow_of_time)