# entropy question **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [August 23, 2006, 9:53am UTC](https://boards.straightdope.com/t/entropy-question/369867 "2006-08-23T09:53:04Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![bbs2k](https://avatars.discourse-cdn.com/v4/letter/b/e495f1/32.png) [@bbs2k](https://boards.straightdope.com/u/bbs2k)\ **Post date:** [August 23, 2006, 9:53am UTC](https://boards.straightdope.com/t/entropy-question/369867/1 "2006-08-23T09:53:04Z")
[Why don’t we consider fire alive? What is life?](http://www.straightdope.com/classics/a971212.html) Oooookay. Now this is gonna sound silly, because the answer I’m sure is right in front of me. But how do trees + plants express a reversal local entropy? Don’t they grow in the path of least resistance sort of like how fire moves? Just at a much slower rate of absorbing fuel. ---
**Author:** ![mrrealtime](https://avatars.discourse-cdn.com/v4/letter/m/e8c25b/32.png) [@mrrealtime](https://boards.straightdope.com/u/mrrealtime)\ **Post date:** [August 23, 2006, 12:56pm UTC](https://boards.straightdope.com/t/entropy-question/369867/2 "2006-08-23T12:56:45Z")
perhaps by “creating” solid wood and fruits etc? Their production of wood, leaves etc. does show recognizable patterns. You could then argue that if the product of something’s existence was utterly random and without pattern, it is not alive. Truly the term “life” is arbitrary and should eventually be retired in favor of a more sophisticated set of terms to settle ethical dillemmas. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [August 23, 2006, 1:08pm UTC](https://boards.straightdope.com/t/entropy-question/369867/3 "2006-08-23T13:08:56Z")
They convert chemicals in ‘uphill’ directions - consider photosynthesis - they contain concentrations of energy in the form of chemical bonds (that can be made to do work when they are broken). Of course, the system as a whole requires a net input of energy in the form of sunlight, and it’s inefficient - not all of the solar energy ends up being stored). But the second law of thermodynamics allows entropy in a system to decrease if there is a net input of energy - i.e. if it isn’t a closed system. ---
**Author:** ![tim314](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tim314/32/3468_2.png) [@tim314](https://boards.straightdope.com/u/tim314)\ **Post date:** [August 23, 2006, 1:20pm UTC](https://boards.straightdope.com/t/entropy-question/369867/4 "2006-08-23T13:20:03Z")
Think about how they look on the microscopic level. As trees grow, they’re creating cellular structure. Fire, in contrast, destroys structure. I’m using a pretty sloppy definition of entropy, but that’s the gist of it. I’m not sure this makes sense as a definition of life, though. Entropy in a (non-isolated) system can decrease for lots of reasons. If you put a hot object in contact with a cold one, the hot one’s entropy decreases as it loses heat. (The [cold one](http://www.homestarrunner.com/sbemail39.html)’s entropy will increase by a greater amount, so the total entropy still increases.) Even if we were to say “Life reduces local entropy without tending towards thermal equilibrium”, so does an air conditioner. ---
**Author:** ![Larry\_Borgia](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/larry_borgia/32/156_2.png) [@Larry\_Borgia](https://boards.straightdope.com/u/Larry_Borgia)\ **Post date:** [August 23, 2006, 5:07pm UTC](https://boards.straightdope.com/t/entropy-question/369867/5 "2006-08-23T17:07:15Z")
I think [homeostasis](http://en.wikipedia.org/wiki/Homeostasis) makes more sense as an indicator of life than simple entropy reduction, for the reasons **tim314** mentioned.