
Originally Posted by
sromag
Hello, I hope this hasn't been discussed before - there's no search function on this forum so I couldn't search.
I have some queries about the 2nd law if anyone is kind enough to answer.
When I was doing engineering at uni, I remember that the 2nd law applies to isolated systems.
My ultimate question is:
Can the 2nd law also ultimately apply to open systems too?
The best I've seen so far is that: The universe can be classed as a closed system so OVERALL, entropy increases over time even though the universe is filled with cases of decreasing entropy... but they are comparatively short lived.
What is a system? How can it be classified?
I.e. the universe is a system... a battery.. a human body, ... a planet.... a species of life... can these be described as systems?
The reason I ask is, for example, that if a planet can be described as a system, then it would be a open system as it is open to everything around it... heat, meteorites, etc.. can it not be said that entropy increases over time there too?
Or a human body.. the body grows old and dies... but it is an open system, (if it can be classed as a system) it will burn out... die and decay... can that be called an increase in entropy?
Thank you.. I hope someone can enlighten me.
I've searched on the net but it hasn't answered this in a very clear cut way.