renewable resources

It's energy differentials, not total, that counts.

The problem is entropy. It is not the amount of energy that determines our ability to use it. It is the energy differentials all over the universe. It's not distributed evenly, so by moving it from some place where there's more to some place where there's less, we get to convert some of it into a form that we can exploit. During that transfer quite a bit of it becomes heat energy and dissipates into a distribution where we can't get any substantive exploitation out of it any more.

If we do that long enough, it ends up being distributed evenly. There's no more way to move any from a place of plenty to a place of dearth.

Eventually every subatomic particle in the universe will have the same energy level. There won't be an average temperature, there will be a universal uniform temperature, some tiny fraction of one degree Kelvin.

That's the problem.

 

"Renewable" energy is local. Entropy is universal.

Resources are only "renewable" within one portion of the universe (such as a planet) and for a limited time (the life of the planet's sun).

Trees store solar energy as chemical energy. When the sun stops providing energy the trees -- in fact all life on earth -- will die.

Wind energy is more complicated, but one major driver of it is the Coriolis effect: lopsided centrifugal force on the surface of a rotating sphere that drags the air in circles. If we tap a small portion of the earth's wind energy it will probably seem very much like an infinite resource. But if we put up enough windmills and they were tall enough, their drag on the atmosphere would eventually stop the winds from blowing and this would cause a slight but measurable slowing of the earth's rotation.

Humans have always regarded the earth's resources as renewable or infinite. Cut down the trees, shoot the buffalo, dispose of sewage in the rivers, pump the petroleum, blow smoke into the air, eat the sharks.

And humans have always been wrong about that because they never understood physics and the concept of entropy until the 20th Century. There's no excuse for it now, I guess a big bunch of us are just stupid.

Many of earth's greatest civilizations fell because they didn't understand that resources are not "renewable" indefinitely. Mesopotamia (the ancient civilization in what is now Iraq) built cities that were fed by widespread farms. The farmers used up the nutrients in the soil until they could no longer support agriculture. A major portion of that region is now desert. The peoples of ancient north Africa (what is now Libya, Tunisia, Morocco, etc.) had farmland that stretched for miles in every direction and was known as "the bread basket of the Mediterranean." They did the same thing. Now it is known by a different name: the Sahara Desert. The Maya civilization that ruled much of what is now Mexico and Guatemala about 1300 years ago built cities and kept sending woodsmen further out into the rain forest to cut trees to use for lumber to build the cities. Eventually they surrounded themselves with barren land that couldn't produce anything and their civilization died as well.

Entropy (the leveling of all energy so that no energy conversion can occur to provide power for biological or mechanical processes) will happen eventually because energy conversion only works one way: toward leveling. However, if you give the human race half a chance, we may be able to accelerate the growth of entropy in the universe. People will say that's crazy, the universe is huge. 2,000 years ago they said the same thing about the Mediterranean Sea.

 

Entropy

I was trying to make that point without getting into a long complicated explanation. It seemed that Mojo was asking for a very high-level conceptual overview of entropy.

Humans have an amazing capacity to refuse to generalize. Well, OK, so we’ve just about used up the fossil fuels. But the energy from the sun or the earth’s rotation is truly infinite, isn't it?

Of course. One always sacrifices precision for simplicity. I’ve seen climate cycles blamed for the downfall of Mesopotamia, and the Mayas were simply not prepared to administer a governmental unit as large as theirs had grown. (Hmm, sounds familiar.) But until now I’d thought historians were nearly unanimous about how the Sahara got there.

Of course. I wish he’d picked an easier example than wind energy but I tried to pick a single factor that would make sense. Everybody learned about the Coriolis Effect from Bart Simpson’s $900 long distance call to the kid in Australia to ask about toilets.