Editing Entropy (section)

=== Relating entropy to energy ''usefulness'' ===
It is possible (in a thermal context) to regard lower entropy as a measure of the ''effectiveness'' or ''usefulness'' of a particular quantity of energy.<ref>{{Cite journal|title=Book Review of 'A Science Miscellany'|journal=Khaleej Times|publisher=UAE: Galadari Press|date=23 February 1993|page=xi|author=Sandra Saary |url=http://dlmcn.com/entropy2.html}}</ref>  Energy supplied at a higher temperature (i.e. with low entropy) tends to be more useful than the same amount of energy available at a lower temperature. Mixing a hot parcel of a fluid with a cold one produces a parcel of intermediate temperature, in which the overall increase in entropy represents a "loss" that can never be replaced.

As the entropy of the universe is steadily increasing, its total energy is becoming less useful. Eventually, this is theorised to lead to the [[heat death of the universe]].<ref>{{Cite book |title =Energy and Empire: A Biographical Study of Lord Kelvin | last1= Smith |first1=Crosbie |last2=Wise |first2=M. Norton |publisher=Cambridge University Press |year=1989 |isbn=978-0-521-26173-9 |pages= 500–501 |author-link2 = M. Norton Wise}}</ref>