unregistered

Sorry if this question is stupid, but how exactly do we know that the universe is more or less chaotic, as opposed to structured? Does it have to do with the probabilistic aspects of QM, or the second law of thermodynamics?

Thanks.

Jesse

What do you mean by "chaotic" vs. "structured?"

unregistered

Ok, let me try and rephrase the question. How do we know that the universe is made up of almost random processes? Someone is telling me that we can't say that the universe is made up of almost random processes because we haven't seen the whole universe.

Is there some kind of scientific law or theory, coupled with observational evidence that leads us to conclude that the universe was not designed, but came about through natural, almost random processes?

Shadowy Man

Who says the universe is made up of random processes?

yguy

How can a process be "almost random"?

contracycle

I think the "almost random" is something of a red herring.

We see no reason to believe that there is an form of plan directing the universe. Objects have properties and act according to those properties; there seems to reason to suspect that there is some sort of order to it all. The only order that is "apparent" is the re-iteration of probabalistic process.

Observation of the entire universe is not a prerequisite for saying the universe appears to be undirected. We have no reason to believe the laws of physics change over space or time meanginfully (they can under some edge conditions).

The person asserting that there IS a plan, or that the unverse is non-random, needs to explain the basis for this claim.

Wyz_sub10

I think it's almost an impossible question to answer in so much as the proponent of "an orderly universe" can always argue that what appears to be chaos is actually very complex order.

(I recently got into this very issue with a Baptist friend of mine who kept pointing to "Chaos Theory" as "proving order").

In any case, the burden of proof remains not on you but on your "adversary".

If his/her argument rests on "we haven't seen the whole universe", then you may as well proclaim that that this unseen portion harbours a gigantic space turtle that controls everything with his mind, or there exists a planet called "Rand McNally" where cats chase dogs and hamburgers eat people. (pardon the Simpsons reference)

However...and I'll let the experts speak to this once they've fniished answering your question with more questions.......QM does demonstrate a certain "randomness" (not the right word, really) in terms of what can be predicted. Likewise, entropy will cause a "breakdown" in systems that cannot necessarily be predcited wither (i.e. where the marbles end up when you smash a jar full of them on the floor). - the latter is where "Chaos Theory" enters.

But even then, these can be argued to be deceptively orderly - kinda like an "everything happens for a reason" mentality.

Shadowy Man

I'm never quite sure what people mean when they claim that the universe is operating under random processes.

What exactly do they mean by random?

For example, Newton's law of gravitation is that the force of gravity between two objects is proportional to the product of their masses divided by the square of the distance between them. Not sometimes the square, sometimes the cube, sometimes none at all. The force of gravity isn't random, things don't gravitate to each other in a willy nilly fashion.

So, when you get two objects orbiting each other, would you say that the process that made them orbit each other is random? Is it directed by some intelligent superbeing? Can you have non-random processes, like celestial mechanics, without an intelligent superbeing directing the action? Can not some simple principles that are inherent in the universe cause these actions to happen in an orderly manner?

Now, if you then want to argue that some intelligent superbeing created the universe with those inherent principles, that's a different story. But just because scientists say that things in the universe happen because of naturalistic processes does not make them "random".

Lobstrosity

I think they probably mean random as in quantum randomness...the fact that at the microscopic level things are governed by probability distributions instead of the cut-and-dry, black-and-white exact conditions classical physics has taught us to think of as a logical necessity. All "random" actually means is that it is fundamentally impossible to predict the precise outcome of any one specific measurement. It says nothing about the behavior of an ensemble, which averages out this unpredictability to produce the classical predictability we observe around us. Ensemble averaging fleshes out the governing probability distribution, and this distribution itself is anything but random. I think people tend to fall victim to the fallacy of composition, assuming that random outcomes in the microscopic world would necessarily result in highly random behavior in the macroscopic world--that quantum physics implies pure chaos. That of course is complete nonsense and only those who know nothing about quantum mechanics would assert such a thing. Secondary to this, people seem to fundamentally misunderstand what is meant when one uses the term "random" in a mathematical/scientific context. "Random" is not synonymous with "chaos"!

Jesse

I'm not so sure it's nonsense. Many systems in nature are nonlinear, which implies sensitive dependence on initial conditions (the 'butterfly effect'), so different possible outcomes at the quantum level could eventually lead to totally different outcomes at the macroscopic level. The tricky part is that the Schroedinger equation governing the evolution of the wavefunction is itself totally linear, so there should be no sensitive dependence on initial conditions in the wavefunction's evolution--so why do we seem to see it at the macroscopic level? The answer should depend on how we resolve the measurement problem, which is still not fully understood. For example, in the many-worlds interpretation one might say that although the state of the universal wavefunction as a whole does not exhibit sensitive dependence upon minor variations in its earlier states, somehow this might not be true of individual "worlds" within the huge superposition (but the definition of 'worlds' in the many-worlds interpretation has never really been clear). Alternately, if one believes that "wavefunction collapse" is a real physical phenomenon, that could provide the source of nonlinearity.

edit: I may have misunderstood what you were saying above--although I still think quantum randomness implies a certain degree of randomness in the macroscopic world due to the butterfly effect, I agree it doesn't imply "pure chaos" in the macroscopic world either. But then again, I wouldn't apply the words "pure chaos" to the microscopic world either.