Time to Think

The Universe's Computer

Erik Benson has had an interesting post on his website about comparing a universe with a computer, and as far as I understand his question is something like this: "How the universe is able to calculate the exact effects of each atom on the other, to infinite accuracy in even simple physical phenomena like throwing a baseball?"

There are many good comments on his weblog about this, but I want to add one more comment to those. There is a fundamental theorem in mathematics called the central limit theorem which basically states that distribution of most random variables approaches Normal distribution in the limit. For example if we drop a box of toothpicks (if you recall from the movie Rain Man!), the toothpicks on the ground will have a pattern similar to the normal distribution, i.e. more thootpicks in the middle and the numbers become less as we get farther away from the center with a rate of decay of inverse exponential. If we mark each of the toothpicks with a unique color, the outcome of the experiment will be the same pattern. There is a similar story in the baseball example too. Each of the quantum particles of the baseball can behave randomly but in average, the whole set of particles will manifest as an object we know as a baseball.

So coming back to the question of throwing the baseball, the nature does not need to do number crunching calculations on the billions of atoms and particles to make sure that the baseball will follow the same path we intended, because the effect of all particles in average is what that is important and that average comes from the macroscopic observations.

Of course, according to the quantum mechanics, there is a tiny possibility (e.g. think of 10 to the power of -1000000!) that the baseball even disintegrates in the air for no specific reason! Or simply pass through the wall! So we can never be sure about the outcome of our experiment either. If we assume that the nature always find the solution with 100% accuracy then we get stuck in the situation that Erik has explained in his weblog but the truth is that it is impossible to have a probability of 1 for anything in the physical world. This is the lesson of quantum mechanic.