randomness

If you ask someone to describe a random process, chances are they will say "A coin toss" or "Throwing dice". In the case of the coin toss, it isn't too hard to imagine that if you knew enough about the coin and the speed and direction of the toss you would know the result of the toss every time. The same thing goes for the dice, but you would have to know a lot more: the physical characteristics of the dice and the surface they're thrown on for instance.

Some clever people might suggest nuclear decay instead of the more hands-on coins and dice. Well, I'm not entirely up to date on the current state of quantum mechanics but I think most physicists would agree to the fact that if we knew everything about the state of a radioactive isotope we would be able to say exactly when it would decay. The problem is: we can't really know and the models we have been using for some time are not good enough to describe this process in a deterministic way.

Isn't this great? No more surprises!

Sorry... there's still the problem with Not enough information...

It is a useful mathematical concept, but one difficult to put into practise; for example, all algorithmic random number generators in fact produce pseudo-random numbers, which means that the periodicity in the numbers generated exists, but has a very long period.

randomness n.

1. An inexplicable misfeature; gratuitous inelegance. 2. A hack or crock that depends on a complex combination of coincidences (or, possibly, the combination upon which the crock depends for its accidental failure to malfunction). "This hack can output characters 40-57 by putting the character in the four-bit accumulator field of an XCT and then extracting six bits -- the low 2 bits of the XCT opcode are the right thing." "What randomness!" 3. Of people, synonymous with `flakiness'. The connotation is that the person so described is behaving weirdly, incompetently, or inappropriately for reasons which are (a) too tiresome to bother inquiring into, (b) are probably as inscrutable as quantum phenomena anyway, and (c) are likely to pass with time. "Maybe he has a real complaint, or maybe it's just randomness. See if he calls back."

Despite the negative connotations jargon uses of this term have, it is worth noting that randomness can actually be a valuable resource, very useful for applications in cryptography and elsewhere. Computers are so thoroughly deterministic that they have a hard time generating high-quality randomess, so hackers have sometimes felt the need to built special-purpose contraptions for this purpose alone. One well-known website offers random bits generated by radioactive decay. Another derives random bits from images of Lava Lite lamps. (Hackers invariably find the latter hilarious. If you have to ask why, you'll never get it.)

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.