What is entropy?

[dejitaru]

If I blow up an apple with a C4 charge, each piece would fall exactly where it should. It's even predictable to some precision.
humans:
Have they actual souls? It seems that any organism is just a mass of molecules directly affected by those which came before them. There is no freedom of choice, only what's hard coded in your brain.

Could we predict or even control random occurences? Lucky basketball shot? Roll 7 every time?
The quadrillions of subatomics particles to be incorporated into some datum cannot be coaxed to hold still long enough for inclusion.
It's an uncontrollable event, so it's 'random'

There is no entropy, only ignorance.

 

[TresLunas]

Like in the Douglas Adams book, The Hitchhiker's Guide to the Galaxy, or one of it's sequels, where the physical state of the whole universe could be extrapolated from a piece of fairy cake (which Zaphod ended up eating).

If the universe is just heaps of matter + the laws of physics, then if you were to take two identical universes and run them side by side, watching them from the outside, events would turn out the same in both universes. A particle in one universe has certain properties (mass, momentum, etc), and it's future is determined by that, and the influence every other particle in it's universe has on it. It's brother in the second universe has the same properties, and is influenced in exactly the same way by the other particles in it's own universe, and therefore has the same destiny.

For the universes to run differently, there would have to be an outside influence, like from a 'spiritual realm'. If we had souls, I suppose that would be your 'spiritual realm'.

 

[Shalmanese]

entrophy is a well defined term and in no way means uncertainty,

Yes, it IS possible for someone to predict the complete actions of the future but WE can't do it since it requires a universe as least as big as ours in order to compute it. Since we dont have access to any spare universes, it wouldn't be possible. Even if we did have access to a spare universe, the fact that we can access it means that we now have to add THAT to the simulation and then we need another two spare universes, continue ad infinitum.

Plus, there are theoretical limits on how we can measure things.

 

[Peter]

Entropy is the state of un-orderedness of mass, qualified by energy level - the lower the energy level, the higher the entropy.

Like when a book falls off the shelf, it's entropy in action - the book lost its height energy in the drop.

The rule of thumb is that all dead material strives toward maximum entropy, while living creatures work against it - or don't, as you can see in my apartment right now :/

 

[FuriousBroccoli]

Sure we have freedom of choice. Just because your actions could be predicted if one could see into the future, doesn't mean they weren't actions chosen freely, does it?

Theoretically, some day we will be able to predict events that today seem unpredictable. Sure, to predict the complete actions of a universe requires another entire universe, but for all practical purposes we'd never want to do that, we'd only want to simulate, and that doesn't require anywhere near that amount of matter, particularly when we consider the need to only simulate a limited scope.

There is of course the little mater of Heisenberg's Uncertainty Principle and quantum mechanics, but it doesn't put a lower limit on the accuracy of our measurements. So who cares about quantum/micro events if they don't scale to the macro level for all intents and purposes.

So it's all about error tolerance. Think about, say, Newton's laws, we know how they work, we don't need to understand the universe at the quantum level to make predictions based on them. So who's to say we do for dice, or the human brain?

 

[f95toli]

There is of course the little mater of Heisenberg's Uncertainty Principle and quantum mechanics, but it doesn't put a lower limit on the accuracy of our measurements. So who cares about quantum/micro events if they don't scale to the macro level for all intents and purposes.

But it does scale to the macro level.We used to belive that quantum mechanics "doesn't matter" for the macro scale,basically that it would "average out". Over the past decades we have started to realize that the micro-and mesoscopic effects do not always average out. There have been a number of papers on how the uncertanty at the quantum-level scales up to the macro level, basically through chaos (remember the butterfly-effect?)

And you are wrong, the ucertainty-principle DOES put a lower limit on how accurate we can measure something (or rather, how accurate we can measure to conjugate variables such as position and momentum), that is the whole point of the principle. Quantum crypthography is based on this fundamental principle.

 

[FuriousBroccoli]

>> And you are wrong, the ucertainty-principle DOES put a lower limit on how accurate

As I understand it, the lower limit is not defined, thus for practical purposes may not exist (though is not mathematically/philosophically zero, but that is of little merit scientifically). I think it was used to be believed that the lower limit was that of the wavelength of a probe in a scattering, which was proven false. Please inform me of any contradictory information, as I'm not an expert in this field, I'm pretty much working from common sense (haha).

As for quantum physics. I know it affects us on the macro level (superconductors for example), but a chaotic system doesn't necessitate a random one at the scale of measurement, so depending on what we are trying to simulate here, do we care?

That is to say, is there a practical limit on what we can measure and predict, given the right tools and rules of how such systems behave?

 

[RossGr]

In Theromdynamics Entropy is defined to be the logarithm of the number of states accesible to the system.
This is a definition which can be expressed mathematically and forms a basis of Thermodynamics (it is a fundamental statement of the 3rd law)

How is it use? The basic definition of temperature is that the inverse of temperature is equal to the change in entropy with respect to changes in Energy. Again a solid mathematical definition.

Mathematical definitions are a requirement of modern Physics, if you cannot express it mathematically it has no value.

 

[dejitaru]

Sure we have freedom of choice. Just because your actions could be predicted if one could see into the future, doesn't mean they weren't actions chosen freely, does it?

Certainly not. I can't control with what brain and environment I'm born. My life is predetermined, and I didn't determine it.

 

[dejitaru]

Of course you only think you have control of your life by the nature of existence.

 

[FuriousBroccoli]

Originally posted by: dejitaru

Sure we have freedom of choice. Just because your actions could be predicted if one could see into the future, doesn't mean they weren't actions chosen freely, does it?

Certainly not. I can't control with what brain and environment I'm born. My life is predetermined, and I didn't determine it.

Brain and environment aside, it's yours to do what you want with. Your circumstances, for better or worse, have nothing to do with free will. Nor does deterministic physics. As I said before, just because your actions could be broken down and predicted, doesn't preclude the notion of free will, even in the philosophical sense. I mean, tell me what you define free will as, and then tell me why you don't have it.

 

[rgwalt]

You forget chaos theory. Some events are not predictable because we cannot determine the intial conditions sufficently. Some systems exhibit no predictable behavior because they are chaotic.

Ryan

 

[Shalmanese]

Another thing on the prediction thingie. Say, you just wanted to predicit this planet, then you would need at least a planet size computer to run the simulation. However, if that computer ever interacts with anything it is simulating, ie. you want to know the results of the simulation, then the simulator is forced to simulate itself which leads to an infinte expansion.

Thus, you can only predict things you cannot do anything about. which makes it kinda pointless.

 

[f95toli]

Originally posted by: FuriousBroccoli
>> And you are wrong, the ucertainty-principle DOES put a lower limit on how accurate

As I understand it, the lower limit is not defined, thus for practical purposes may not exist (though is not mathematically/philosophically zero, but that is of little merit scientifically). I think it was used to be believed that the lower limit was that of the wavelength of a probe in a scattering, which was proven false. Please inform me of any contradictory information, as I'm not an expert in this field, I'm pretty much working from common sense (haha).

As for quantum physics. I know it affects us on the macro level (superconductors for example), but a chaotic system doesn't necessitate a random one at the scale of measurement, so depending on what we are trying to simulate here, do we care?

That is to say, is there a practical limit on what we can measure and predict, given the right tools and rules of how such systems behave?

Yes:
(The uncertainty in position)x(the uncertainty in position) is bigger than h/(2*pi)=1.06e-34
This is the Heisenberg uncertainty principle and it has never been proven wrong.

The point I was trying to make was that the randomness at the micro- and meso- scale can be "amplified" to the macro level through chaos, I now chaos does not neccesarily imply randomness but in a chaotic system even a small random event will eventually affect the whole system.

 

[sil0net]

Determinism?

 

[stebesplace]

entropy is also a discontinued render engine used in conjunction with PRMan with Pixar's own scripting language. It was written by two men that left Pixar to for their own company, Exluna. Now that Exluna was just bought out by Nvidia, Pixar sues them for using patented material in their render engine. So, no more BMRT or Entropy.

I know this is probobly not what you wanted, but it relates to your original question.

-Steve

 

[Peter]

Gah. We're all just here to compute the question to which the answer is 42.

 

[dejitaru]

Gah. We're all just here to compute the question to which the answer is 42.

Well, if you're still working on the question, the answer could be anything. I like 43 better.

 

[Peter]

Originally posted by: dejitaru

Gah. We're all just here to compute the question to which the answer is 42.

Well, if you're still working on the question, the answer could be anything. I like 43 better.

Nono, the answer has been computed already. Mr. D. Adams will explain that to you.

 

[TresLunas]

Yes, yes, yes, we all know the answer, but what's the Question?


Actually this might explain what entropy is.