true randomness

July 1, 2009

We’ve all rolled dice in board games and are confident that those rolls are truly random, i.e. not dependent on any measurable forces. We can’t recreate or predict any type of roll. You’ve probably also flipped a coin, which might seem easier to fix but have probably met a good deal of frustration if you tried to do so.

We take this kind of randomness for granted, but what’s interesting is that for all of our computational prowess, we are unable to create random numbers in computers. Of course, we can create pseudorandom numbers, but not the real deal.

Computers often generate pseudorandom numbers using a starting number, or seed, and then complicated functions to get the next random number. If you supply the same seed number to the randomizing function, you’ll get the same (infinite) stream of “random” numbers out. This property of pseudorandom numbers is actually quite useful when building and debugging computer programs because it allows the programmer to recreate seemingly random scenarios for testing.

When computers are actually trying to generate random numbers, they often use the clock’s timestamp as a seed, since it’s never the same. While this technique does generate a random stream of numbers it’s still, in a way, determined. We can predict what a random number will be given a seed value at a specific time.

In order to achieve true randomness, programmers have had to turn to the real world. Sites like random.org, which generates random numbers from atmospheric noise, and (more recently) the Dice-O-Matic hopper, which physically performs millions of dice rolls today (follow the link for a cool video of it in action), serve up genuine random numbers.

What’s interesting is that, in theory, these numbers aren’t really random either. Sure, they’re products of chaos theory, but they each have predictable forces acting upon them that cause them to behave in a predictable way (remember quantum uncertainty operates on much, much smaller levels than dice rolling). What makes them basically random, though, is that there are so many interacting forces, it’s impossible for us to compute with today’s computing power. But Laplace’s demon could figure it out, which makes me wonder if at some day in the future we won’t be able to predict the outcome of a dice roll, taking us one small step further to predicting the future itself.

(I’m currently reading a very interesting book by Daniel Dennet entitled Freedom Evolves about how to have free will in an determined universe. If this kind of stuff interests you, I’d certainly recommend it.)

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