My biology teacher says nothing in the universe is random. I’m not sure if thats true. Can’t computers select numbers randomly? What about Pi?
She said drawing a playing card from a deck isn’t random because you actually chose which card is to be removed with your hand.
What do you think?
~yawn~ going to bed
Ask her about Quantum Physics.
just a second to what Urban Ranger said - there is a whole area of physics that deals with the ‘randomness’ of matter at smaller than microscopic levels. In fact, IIRC, it was quantum theory that put the kaibosh on the early 20th cetury belief that we could one day use science to predict anything (or go back into history to see what happened) if we knew the state of all relevant actors now.
As far as a computer-generated random number; no, those are ‘random’ for all intents and purposes, but are actually created using an algorithm that runs off of CPU clock cycle (I think - if I’m wrong I will be corrected for sure, but Iknow they are not truly ‘random’). PI is anything but random, it will always be the same, but the digits themselves are non-repeating so appear to be ‘random’.
Lots of stuff at the sub-atomic level is random. For example, the time it takes for a specific radioactive atom to decay is random; even though with large groups of these atoms we can calculate the probility of that atom decaying within set period of time, allowing us to get the half-life of a element, there is no way to know ahead of time which specific atoms will decay.
In addition to truly random events already described, many phenomena are so unpredictable that they might as well be random. Rolling dice, for example, is predictable in theory but in practice the tiniest change in initial conditions will make a huge difference in the outcome. Weather patterns, fluid flows and other so-called “chaotic” systems fall in this category. (However, an amusement parks featuring prehistoric animals does not fall in this category.)
Computers can’t generate truly random numbers. Everything a computer does is strictly governed by precise rules and what its input was, so with enough information about its state and the rules it’s using you can absolutely predict what it will output next. This is a significant problem in cryptography, where the security of the key is dependent upon how random it is. There has been a lot of effort expended to develop pseudorandom number generators that can produce output that looks highly random but will, eventually, begin to repeat itself.
The only way to get a computer to generate random output is to feed it random input. That’s where services like HotBits come in: HotBits uses the decay of radioactive elements, something completely random, to generate completely random data it will then send to anyone online.
Cheaper methods of generating random noise involve using different kinds of noisy diodes or even Lava Lamps. 
So computers cannot generate random numbers by themselves, but they can take advantage of natural randomness to perturb otherwise completely norandom, or deterministic, computations.
Damn. In my last sentence, change norandom to nonrandom.
I suspect you could generate fairly random numbers by monitoring the spelling on the SDMB. 
This is something which has interested me for some time, but I am far from an expert, so I’ll try to describe some general ideas and hope that some real mathematicians will happen along and straighten out any mess I might make.
My understanding: some mathematicians argue that there is no such thing as a “random” number, but this is more a philosophical issue having to do with what “random” means rather than a “real world” issue (though it may have “real world” implications).
Assume that “random” means a complete lack of order or predictability.
When we roll a die, we say that it is a “fair” or “random” die if each of the six numbers has an equal chance of appearing on each roll. But if we roll such a die 6,000 times that means we should get almost exactly 1,000 ones, 1,000 twos, etc, etc. In other words, we expect that “random” die to behave in a very “orderly” manner in the long run. And that’s not random. It is, in fact, very predictable. According to our definition, a truly “random” die might give nothing but threes or it might land on five every other roll. There should be no way to predict. But we would call such a die “non-random” because it fails to behave in the “orderly” and “predictable” fashion that we expect from a “random” die. See the problem?
Another point. Most of the time we aren’t trying to generate truly random numbers at all. Generally we are trying to generate something along the lines of a single digit number between zero and nine or a double digit number between zero and 99, etc. These constraints impose a certain order on the result which prevent it from being “completely” random. According to this line of thought, a number can only be “truly random” if it can be any number from zero to infinity, since this would impose no constraints at all.
But, assume that you have just bought a “random number generator” which is supposed to “randomly” generate numbers from zero to 99 to five decimal places. When you get it home you have it generate a couple of thousand numbers and, much to your surprise, every number that it generates is less than one. Now the odds of getting one number less than one are 1/100. The odds against two numbers, both less than one, are 1/10,000 and so on and so forth. Obviously the odds of every single number being in the lowest hundredth of the possible range are so astronomically small that you would have to conclude that your “random number generator” isn’t really random at all.
But now assume that you’ve bought a generator that is supposed to generate random numbers from zero to infinity. Well, the problem is that no matter what number it generates it is a simple matter to show that that number is at least in the lowest hundredth, or lowest thousandth or billionth or whatever you choose, of the possible range. Since the odds against a “truly random” number always being so small are as astronomical as you wish to make them, one has to conclude that “any number,” no matter what it is, isn’t really random.
There have been at least two long threads on this same question lately. Try a board search for “random” and “randomness” in the title.
If you flip a coin, if you knew the exact force that was put on the coin by your fingers, could figure out the effects of air movement, gravity, etc. on the coin, you could theoretically predict whether it would come up heads or tails. However, since you’d have to measure too many things that we don’t have sensitive enough instruments for it might as well be random. You can extend this same argument to say basically that at the time of the big bang, the fate of every atom in the universe was already decided, so nothing is truly random.
The obvious counter-argument to this is that since we can’t know all of the information necessary to predict certain outcomes, that those things are by definition random.
So, in a way you are both right.
By the way, your desktop PC typically generates a random number by taking the current time and using that as a “seed” into a formula which generates a psuedorandom sequence of numbers. Since the sequence comes from a formula, the sequence of numbers isn’t truly random (hence it is called “psuedorandom”). The only random part of it is the particular time which you choose to start the program at, which determines the seed value. Programmers have to be very careful using random numbers in computers, because since they aren’t really random, if you use them in certain ways the result won’t be random at all.
Could someone more familiar with quantum physics clear something up for me? It seems to me that QP admitted the possibility that the universe was deterministic. The Heisenberg uncertainty principle, for example, doesn’t say that the position/momentum of a particle is really indeterminate; rather, it just says that we can’t measure the position and momentum with complete accuracy. Is there any reason in quantum physics why any phenomenon couldn’t be completely deterministic, provided that the deterministic factors which influence the phenomenon are beyond our ability to observe?
Whether or not the behaviour of a die is predictable depends entirely on what you’re trying to predict. For example, if I roll a single die I can predict with some confidence that I won’t get a one. I’ll be wrong occasionally, but on the whole it’s likely that I won’t get a one. So I can “predict” the behaviour of the die as long as I don’t try to be too specific; the exact outcome of the roll is completely unpredictable but it is predictable that the outcome will lie in a given set of possible outcomes, provided that that set of outcomes is nice and big.
The same thing happens when you roll a die 6000 times. When you predict that there will be almost exactly 1000 ones, etc., you’re actually making a prediction that encompasses an enormous number of the 6[sup]6000[/sup] possible outcomes. There are just more outcomes with about 1000 ones than there are outcomes with all threes. So the behaviour of the die is “predictable”, but only at a very coarse level. If you try to predict the specific outcome (i.e. “3, 1, 5, 3, 3, 4, 1, 6, 2., …”) you won’t be able to do it.
This also relates to the difference between mathematical randomness and our perception of what “looks random”. The “all threes” outcome only looks less random than “3, 1, 5, 3, 4, 1, 6, 6, …”; both outcomes are in fact equally likely. It’s just that, again, there are more outcomes that look like the latter than the former.
Since we can’t measure perfectly a particle’s position in space and its momentum, it is impossible for us to perfectly predict in determinstic outcomes. Where an event is chaotic, this imprecision really bites you on the ass. It’s not just a matter of saying, “well we can’t do it now, but theoretically if we could measure it then it wouldn’t be ‘random’”. It’s a matter of saying, “it is actually theoretically impossible to perfectly measure this, so the practical effect is that the event is random… at least to us”.
The “at least to us” part is pretty critical. What other kind of “randomness” could you really be referring to?
That aside - it would appear that some events really are random. The classic example is certain types of radioactive decay - the time at which a particle is emitted is a random event.
“Randomness”, or at least probabilistic events, occur elsewhere too. In fact, they occur everywhere. When you get right down to it, a particle is not a solid object (at least quantum mechanically). Rather it is merely a probabilistic waveform. It isn’t “at position x”, it is at position x with probability f(x).
This is, to say the least, not an intuitive concept to get your head around. But it does lead to some beautifully elegant results.
pan
(Needless to say, “probability f(x)” should be probability density function f(x)")
I am not an expret in quantum theory, but I recall hearing or reading that, even were it possible to know all of the required information at a particular time, it would almost instantly become irrelevant, as quantum theory tells us that electrons (which have mass) will sometimes randomly appear in a place that was “empty” previously, and othertimes will randomly vanish! So the Map of the Universe (or even of the earth’s atmosphere) that you so painstakingly constructed, will instantly become obsolete, as new electrons will instantly appear in spots you can’t predict, and existing electrons will vanish, promptly throwing off all of your future predictions in unpredictable ways.
Does this sound correct?
Raise your hand in class and ask your biology teacher how her conception of a wholly determinate universe comports with free will.
What would your BIOLOGY teacher know about math and physics anyway?
(Sounds to me like she doesn’t know much.)
A biology teacher espousing determinism? What do you think their view on evolution is?
While mutation rates in species can be generally determined, individual mutations are random.
Determinism has its place, even in the sciences. Computers are purely deterministic devices, and any “random” numbers they generate are not truly random.
On a slightly unrelated note, All intel motherboards since the i81x series come with a true Random Number generator onboard and rumour is that the new Via C3 CPU’s are also including a true RNG. However, I dont know who if anybody actually uses it.
A teacher once said that to me.
I then screamed out “I AM SATAN!”
Followed, a few seconds later, with, “That was random.”
Luckily, my teacher had enough of a sense of humor not to send me to the dean…