Isaac Asimov was one of the best science fiction writers of the world. He writes about a multitude of different themes, some of which I'm really fond of (Artificial Intelligence!). Asimov is one of those writers that I've always want to read works from. Tonight I read for the first time one of his stories, and I have to say, I'm not disappointed.
The Last Question is about entropy, which is basically a measure of disorder in a system. In other words, disorder refers to the number of different "states of all the molecules making up a system" that the system can be in. As a simple example, suppose that you put a marble in a large box, and shook the box around, and you didn't look inside afterwards. Then the marble could be anywhere in the box. Because the box is large, there are many possible places inside the box that the marble could be, so the marble in the box has a high entropy. Now suppose you put the marble in a tiny box and shook up the box. Even though you shook the box, you pretty much know where the marble is, because the box is small. In this case, the marble in the box has low entropy.
If you remember your high-school science lectures, the first law of thermodynamics is the law of conservation of energy. That law states that the total energy of an isolated system remains constant. Energy can be neither created nor be destroyed, but it can change form. For instance, chemical energy can be converted to kinetic energy in the explosion of a stick of dynamite.
A consequence of the law of conservation of energy is that no system without an external energy supply can deliver an unlimited amount of energy to its surroundings.
Entropy is the basis for the second law: the Universe evolves such that its total entropy always stays the same or increases. Unlike energy, entropy can be created. In fact, your body is creating some right now as it generates heat. One of the reasons that you have to sweat off water when your body is too warm is that you have to get rid of the extra entropy (otherwise, you would become disorganized and eventually die). The energy that your warm body radiates also carries away the extra entropy. It does this because losing this energy decreases the number of microscopic states that the atoms and molecules of your body can be in.
[SPOILER ALERT]
You may have read the story before (or following the link I just posted), and read that humans built a super-computer to manage and calculate everything. As billions of years pass, humans of different eras ask the computer if it's possible to reduce the amount of entropy. The computer knows that eventually it will have enough data to know the answer, but that takes quite a long time. So long, that humans have actually all disappeared and merged with the computer itself. To prove that final question of whether entropy can be reversed, the computer, or God, reshapes the universe with the mystical words "Let there be light!".
Fuckin' hell, that was some short story. When I was a kid in sixth grade, I told my friends that one day, the universe would stop expanding, start contracting and eventually have a massive explosion back at it's center. The explosion would generate so much energy that it bend time and would act as the Big Bang, taking us back around the circle. That was, of course, quite naïve, but it's nice to see that a quite renowned science fiction writer has a similar idea to mine.
Anyway, Asimov's story is based on the fact that "no problem is insoluble in all conceivable circumstances" and that the computer will eventually break the 2nd law of thermodynamics and revert entropy. While it may be impossible, it would be quite spectacular to witness such an event, but ultimately something so distant from us that we can't even conceive it in our small brains. You, me and anyone else that reads these words will be long gone before the Sun even runs out (the exact same reason the book's first characters ignored the problem!), so there is no need to lose your sleep over this problem.
Hoping you enjoyed this story,
David
PS: thanks to the New Mexico Solar Energy Association for their post on entropy, of which I quoted a lot of information
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