True randomness, lava lamp and atmospheric noise

What is the link between a lava lamp and random number generation ?

Assessing what is random and what is not is not easy; after all a dice and a flipping coin are only ruled by basic rules of mechanics. We say that it is random only because it is hard to predict. When you ask your computer for a random number, there is nothing really random in it either, since a computer can only run predefined methods. This is illustrated by a famous quote from John von Neumann:

Any one who considers arithmetical methods of producing random digits is, of course, in a state of sin.

Well then, how can we really choose random digits? This website

http://www.random.org/

proposes random numbers generated from atmospheric noise picked by a radio. In some sense, there is probably nothing random in it either, but it is hard enough to predict so that it can be considered as true random numbers. From the website:

People use RANDOM.ORG for holding drawings, lotteries and sweepstakes, to drive games and gambling sites, for scientific applications and for art and music.

And indeed on their website there are random generator for drawing dices, cards, calendar dates or even Jazz scales.

Apart from using atmospheric noise, there are other fun ways to catch some randomness, including taking pictures of a lava lamp and analysing the patterns, or timing the decay of a radioactive source, which is considered to be truly random, in the sense that a stochastic process rules the decay. Of course all these methods allow to draw only a few numbers at a particular time, but that can still be useful as a seed for a pseudo-random generator, or in cryptography. More information can be found on this page.