Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: another_someone on 20/12/2005 14:17:01
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Is the complexity of the visible universe increasing, reducing, or remaining constant?
The factors that I would imagine to impinge upon this question are:
1.The amount of matter in the universe.
Assuming a constant complexity in the relationship between the component parts of a system, the fewer the parts, the less the complexity of the overall system.
As far as I understand, we seem to be losing matter from the visible universe. We are losing matter into black holes (although there has been some discussion about whether we might ever recover some of this matter), and we appear to be losing matter through a much grander event horizon, the distance that is far enough away that light will never reach us (from what I hear, some parts of the universe are expanding sufficiently fast that light that presently reaches us from those part will not reach us in the future, and thus those parts of the universe will have left our visible universe).
2.The amount of entropy in a system.
The greater the amount of disorder in a system, the greater the inherent complexity of the system. Since the second law of thermodynamics states that entropy increases over time, thus complexity must increase over time.
3.The scale of uncertainty in the system.
Heisenberg's uncertainty principle tells us that there is a limit to the amount of precision with which we can describe the universe. If two states cannot be distinguished, then they must be regarded as being the same, and there being no information or complexity that can be used to distinguish one state from another.
The question is whether the degree of uncertainty remains constant over time, or is there an increase in the scope of uncertainty (and thus a decrease in information and complexity), or a decrease in uncertainty (and thus an increase in the number of discernible states, and thus an increase in complexity).
I apologise if some of my assumptions are erroneous or naïve.
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Since the second law of thermodynamics states that entropy increases over time
Actually it doesn't. It states that the entropy of a system can never decrease. That's different from saying it increases.
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quote:
Originally posted by DoctorBeaver
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Since the second law of thermodynamics states that entropy increases over time
Actually it doesn't. It states that the entropy of a system can never decrease. That's different from saying it increases.
My apologies about the imprecision, but is it in any practical sense any different.
Unless there is a conservation of entropy, does it not follow that if it does not decrease then it must increase – or are you saying that we do not know if it is conserved?
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I was looking up something yesterday to do with a totally different subject & came across a piece on this. It was to do with the total energy level of the universe being zero and the entropy of the universe was brought into it. I'll try to find it again as it was quite a good piece. Unfortunately I didn't bookmark it so I'll have to trawl through all the Googled stuff again to find it.
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These aren't the 1 but they're quite interesting
http://www.boloji.com/perspective/076.htm
http://www.chiark.greenend.org.uk/~sbleas/creative/entropy/#33
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I can't find it. It was 1 of those link->link->link trails from what I was looking up.
If I remember rightly, though, the argument put forward was along the lines of all energy in the universe being balanced and therefore = zero and there always being a constant amount of energy available to do work, therefore entropy also = 0. I can't remember it exactly.
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It depends what you mean by complexity and the way the question is phrased seems to suggest that you do not tefine it in the same terms that I do. In my book complexity as nothing more to do with entropy than obeying the second law of thermodynamics. Nothing to do with the number of protons electrons etc in our universe, and nothing much to do with hisenberg uncertainty, but it does have a lot to do with things that we can distinguish. Individual people are substantially similar but and all have unique life histories and can tell you about them if you ask them they are really complex. Amoebas are very similar to each others and can be considered to be clones but they can reproduce and control their environments in simple ways they arent so complex. Stars are pretty big things but their life history is virtually totally determined by the mass of material of which they are made unless they are closely associated with other stars. so stars are pretty simple things.
Now to try to answer the question. The universe appears to be cooling down and most of it is too cold for life as we know it to flourish but there are and will continue to be plenty of hot spots in the form of stars with planets to allow life to form. Human beings are almost clever enough to design and build an Ark with which a significant number could live indefinitely in interstellar space and become independant of our star the sun so on the whole I think that complexity is likely to be increasing
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OK, I suppose in order to understand what I mean by complexity, I should explain how I came to think about the question.
It was considering the notion of modelling the, or a, universe on a computer (or information processing engine of some sort). How would the entities within that model be able to tell whether the world around them was real or merely a computer simulation.
In reality, there is no way that anyone within the hypothetical computer simulation could possibly know they were part of a computer simulation, but there are certain constraints that would apply to a simulation model, which if not adhered to, would make a computer simulation an impossibility. One such constraint is that the amount of information stored within the model would be finite.
In the first instance, Heisenberg's uncertainty principle is a minimum requirement, since it provides a finite limit upon the precision of information that is capable of being known about any particle in the universe, and so is capable of being modelled using finite precision mathematics. The classical model of the universe would have required information about each particle to be known to an infinite precision.
Beyond that, a universe with a very high degree of order needs only a very small amount of information known about it in order to describe it. As the degree of order in the universe decreases, so the amount of information one needs to store in order to map the universe increases, as one can no longer rely on the ordered relationship of the component parts to predict where particles are (an interesting corollary is that the development of complex life only occurred after the universe had substantially aged, and could not have occurred in an earlier part of the universes history). Thus, if our universe continues to become ever more disordered, if there is no compensatory mechanism that removes information from the universe, then it precludes the possibility that our universe is merely a model within a finite sized information processing engine.
Clearly, there are mechanisms that do remove information from our visible universe, but the question is whether they are sufficient in order to maintain a finite limit to the amount of information that would remain within our visible universe in order that it could be potentially modelled by some extra-universal computing engine.
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Originally posted by Soul Surfer
It depends what you mean by complexity and the way the question is phrased seems to suggest that you do not tefine it in the same terms that I do. In my book complexity as nothing more to do with entropy than obeying the second law of thermodynamics. Nothing to do with the number of protons electrons etc in our universe, and nothing much to do with hisenberg uncertainty, but it does have a lot to do with things that we can distinguish. Individual people are substantially similar but and all have unique life histories and can tell you about them if you ask them they are really complex. Amoebas are very similar to each others and can be considered to be clones but they can reproduce and control their environments in simple ways they arent so complex. Stars are pretty big things but their life history is virtually totally determined by the mass of material of which they are made unless they are closely associated with other stars. so stars are pretty simple things.
Now to try to answer the question. The universe appears to be cooling down and most of it is too cold for life as we know it to flourish but there are and will continue to be plenty of hot spots in the form of stars with planets to allow life to form. Human beings are almost clever enough to design and build an Ark with which a significant number could live indefinitely in interstellar space and become independant of our star the sun so on the whole I think that complexity is likely to be increasing
Learn, create, test and tell
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I suppose to answer your question as close as I can, I was defining complexity as the number of parameters that have to be managed to describe all the objects in the universe.
As you say, humans are far more variable than amoebas, so the number of parameters that need to be managed to describe a human is greater, but then there are far fewer humans than there are amoebas, so looking at how much information has to be managed for all amoebas may be comparable to the amount of information that has to be managed to describe all humans. In fact, one could even go further, and suggest that as human population has increased, so the diversity of non-human life has reduced.
I am not so sure that humans will themselves ever be able to travel in interstellar space, but I could well imagine that we could build robots that would do so. Given the history of human occupation on this planet, that has increased their own complexity while restricting the space available for other species to survive, can we predict whether overall human occupation (whether directly, or by robot proxies) will increase, reduce, or maintain a similar complexity elsewhere?
But, beyond the issue of the complexity of molecular chemistry (as expressed in living organisms), am I right is believing that as the universe has cooled, the number of forces in the universe has increased (e.g. the weak and electromagnetic force were one and the same, until the universe cooled enough to split them into to separate forces). Could this continue further?
On the other hand, as the universe cools, is it not the case that the range of energy states particles can exist in reduce, and so reducing the complexity of the universe in that way?
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I agree it would be a lot easier to send robots to the stars than humans because of their less stringen environmental requirements but they would have to be self replicating and repairing robots and that might be more difficult.
As the universe cools it becomes possible for more finely divided energy states to exist without them being disrupted by the local temperature. To have any sort of life you need it to operate at a temperature where its chemical reactions are not totally stable. The carbon based chemistry of life appars to be the only one with sufficient complexity alhough I have read books that investigate other chemistries. There is also the question as whether electromagnetic lifeforms could exist on stars 'cos there's plenty of them around.
Coming back to your thoughts about comuter model universes. Is this related to a matrix thipe idea in which "reality" is in fact a computer programme?
if so its easy to kill the possibillity that our reality is a computer programme by considering the communications requirements (and the lack of glitches :-)
Learn, create, test and tell
evolution rules in all things
God says so!
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quote:
Originally posted by Soul Surfer
]I agree it would be a lot easier to send robots to the stars than humans because of their less stringen environmental requirements but they would have to be self replicating and repairing robots and that might be more difficult.
I don't think one should be looking towards self-replication in the narrow sense of the word. One needs an environment where the overall system is capable of self-replication, but not necessarily its component parts.
Most of our factories are already substantially run by robots, so the idea of robots building robots (at least in large factories) does not sound incredible. Miniaturising the process so that one could fit the robot factories inside spaceships is the one issue, and getting it fed with raw materials is another. None of these are unimaginable objectives to achieve.
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As the universe cools it becomes possible for more finely divided energy states to exist without them being disrupted by the local temperature. To have any sort of life you need it to operate at a temperature where its chemical reactions are not totally stable. The carbon based chemistry of life appars to be the only one with sufficient complexity alhough I have read books that investigate other chemistries. There is also the question as whether electromagnetic lifeforms could exist on stars 'cos there's plenty of them around.
Indeed, as you say, one has to be careful about what one classifies as 'life'.
What I was talking about was information complexity, and in that regard I was looking at life as simply being a complex bunch of information. There are many non-chemical ways in which one can have similar levels of complexity of information – whether one wishes to regard them as life or not is a separate philosophical question.
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Coming back to your thoughts about comuter model universes. Is this related to a matrix thipe idea in which "reality" is in fact a computer programme?
if so its easy to kill the possibillity that our reality is a computer programme by considering the communications requirements (and the lack of glitches :-)
Others have in the past also related it to The Matrix film. I have not been to the cinema in about 30 years, and have not seen The Matrix, but from what I understand, it is substantially Hollywood, and not the inspiration for my idea.
If there was an inspiration for the thought it probably had more to do with cellular automaton simulation programs then simulate at a simple level how primitive organisms might interact within the environs of a simplified computer simulation.
Converging upon that is another philosophical issue. Over the last few centuries, we have very much been in the age of the machine, and with this have developed a very mechanistic view of the universe. We are now entering the information age. It would be reasonable to ask whether, as we increase our understanding of the behaviour of information, we would not naturally apply that understanding to a different philosophical view the cosmos, just as the our understanding of the machine drove our earlier philosophical perspective of the cosmos.
I am not sure what you mean by communication requirements?
The issue of glitches is something I too was thinking about. Firstly, the issue only really arises if one thinks of the 'computer simulation' as being something devised by a sentient being. If it is merely regarded as a way of visualising a naturally occurring reality, then one does not need to look at 'human error' (or should that be 'sentient error'?).
Even if one does take into account 'sentient error', how would we be able to discriminate between error and intended outcome? Without having original design documents to hand, how would you determine error?
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If you like cellular automata and computer programmes, have you read Stephen Wolfram's "A new kind of Science" I've hot through about half of it so far but I am not activley reading it at the moment. That shows how the most beutiful complexity can come out of the simplest algorithms and I do tend to think that when we get down to quantum gravity some of his approaches could be very valid.
I am a strong believer in the effectivenes of Occam's razor ie the simplest solution is probably the best and right one. ie real reality being viewed by my personal computer model called "consciousness" interfacing via real reality with your real reality being viewed by your personal computer model called "consciousness"is by far the simplest. this gets rid of all the communications that would be needed to render everyone else's models consistent.
Dont get me talking about information! Ive made my substantial crust by understanding that a bit better than most. it really is important and I could go on for ever!
Learn, create, test and tell
evolution rules in all things
God says so!
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Not heard of Stephan Wolfram before.
Had a quick internet search for him.
He seems to provide some interesting engineering solutions, but it is not clear to me that he is dealing with science as such.
In particular, science is the art of prediction, it is the art of constraining the infinite possibilities of tomorrow by demonstrating what is impossible, and showing that what is left is all that is possible. From what little I have seen (and maybe you can correct me on this), Steven Wolfram does not prove anything to be impossible (although he shows a lot of things to be possible, but from my brief search, I did not see him applying any constraints upon the possible – but then, maybe your having read his work in more detail will enable you to tell me that I have totally misjudged him).
What I was speculating upon was whether there might be laws of conservation of information (or, maybe better expressed as, conservation of complexity) of a similar nature to laws of conservation regarding energy or spin. In that respect, I would regard cellular automata, as any other computer simulation, as useful test beds to understand how scientific theory might manifest itself, but not as a substitute for scientific theory.
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Stephen Wolfram originated "Mathematica" the mathematics tool that most scirntists use to help them with their maths and produce predictions! he is a Guru of the same order as Bill Gates altough I think that his recent work suggesting that we could learn everything by mathematical synthesis is a bit off the rails. Mathematics is so much bigger than physics (or anything else for that matter) in terms of possibilities that unless you can have a good idea that you are likely to hit "pay dirt" you could just be amusing yourself. Although thinking aloud it might be possible to develop some sort of "evolutionary mathematics" that could help.
Learn, create, test and tell
evolution rules in all things
God says so!
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coming back to your "conservation of information" suggestion. The laws of thermodynamics are effectivlely this. Hence the big argument with Stephen Hawking and A N Other(can't remember his name at the moment)about the loss of information into a black hole and the entropy of a black hole which Stephen conceded recently saying that the info that went in could well come out as it evaporates.
Learn, create, test and tell
evolution rules in all things
God says so!
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quote:
Originally posted by Soul Surfer
coming back to your "conservation of information" suggestion. The laws of thermodynamics are effectivlely this. Hence the big argument with Stephen Hawking and A N Other(can't remember his name at the moment)about the loss of information into a black hole and the entropy of a black hole which Stephen conceded recently saying that the info that went in could well come out as it evaporates.
Learn, create, test and tell
evolution rules in all things
God says so!
Certainly, black holes are one thing, but not the only instance of loss of information.
If, as I understand it, the outer edges of our visible universe are disappearing because they are expanding faster than light can reach us from them, then that is another sort of event horizon, and thus involve the loss of information.
http://www.space.com/scienceastronomy/universe_end_011212.html
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Loeb, a theoretical astrophysicist at the Harvard-Smithsonian Center for Astrophysics, peers through Einstein-colored glasses. His view of the end of the visible universe is rooted in the General Theory of Relativity and based on the notion that everything is expanding at an ever-increasing pace.
All distant galaxies are moving away from us and moving faster all the time. Few researchers debate this point. Few have predicted its ultimate consequence quantitatively as Loeb did.
Eventually, Loeb says, galaxies will recede at the speed of light, making it impossible for their light -- or any other radiation or information -- to traverse the cosmos to our home in the Milky Way Galaxy.
"Any given source accelerates away from us and eventually reaches a speed larger than the speed of light so that photons emitted from it cannot catch up with the cosmic expansion, relative to us," he said.
Already, galaxies more than 6 or 7 billion light-years away are beyond contact, Loeb figures. Such galaxies, measured by astronomers to have a redshift of 2 or more, will not be able to transmit any signal to us in the future due to the accelerated expansion of the universe.
"Suppose there are extraterrestrial civilizations in these galaxies," Loeb said in a telephone interview. "If we send a signal to them now, they will never see it."
Like black holes
The point of no return for these galaxies in called an event horizon, a concept more commonly used to describe the hypothesized sphere around a black hole beyond which nothing, not even light, can escape
Another factor is the cooling of the universe. As matter cools, it tends to condense into ever more rigid structures, and these rigid structures inevitably are less complex than their hotter counterparts. Ofcourse, the counter-argument to this is that intelligent life could (as far as we can ascertain) only exist in cooler periods – albeit, this is a highly localised phenomenon is comparison to the more universal condensation of matter.
One other intriguing issue that occurs to me in this respect is the phenomena of entanglement. If two particles are entangled, then they must share information. This implies that as an entangled pair, they must contain less information than they would as two unentangled particles. This would imply that the process of entanglement must destroy information, and the process of disentanglement must create new information.
The problem with all of the above, whether true or not, is that they are qualitative suppositions, and for any rational application of a law of conservation, one must be able to make quantitative measurements and predictions.
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You have some fundamental errors in what you consider to be information and complexity if I have a box containing a gas it is very simple and can contain very little information as all the molecules obey simple laws and are largely indistinguishable If I now freeze this gas into a liquid and then a crystalline solid it can contain much more information because the cryatals could be of many sizes and orientations depending on how I do the freezing because the act of freexing fixes the information about how I did it. This is precisely the opposite of what you are saying above.
Learn, create, test and tell
evolution rules in all things
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quote:
Originally posted by Soul Surfer
You have some fundamental errors in what you consider to be information and complexity if I have a box containing a gas it is very simple and can contain very little information as all the molecules obey simple laws and are largely indistinguishable If I now freeze this gas into a liquid and then a crystalline solid it can contain much more information because the cryatals could be of many sizes and orientations depending on how I do the freezing because the act of freexing fixes the information about how I did it. This is precisely the opposite of what you are saying above.
Learn, create, test and tell
evolution rules in all things
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I think there is something of a difference in nomenclature (I'm not saying that your use of nomenclature is wrong, only that I clearly have not expressed myself properly).
If you have a cubic crystal of atoms of 1000 atoms on each side, at a specified location, oriented in a particular direction, and at zero kelvin, with a given atomic spacing, then with that simple description I have accurately described the location of 1 billion atoms.
If those atoms were in a gas, then I would need to provide 1 billion separate descriptions for each atom in the gas; and clearly that would need a far greater amount of information to describe it than would need to describe the atoms in a crystal.
I accept that these are idealised situations, since I have assumed a perfect crystal (without any imperfections or impurities) and at absolute zero temperature. Any violations of those assumptions would mean that the information describing the atoms in the crystal would only be approximate, but nonetheless would be far more accurate than any attempt to describe the atoms in gas using a similar amount of information would give.
What you say about freezing being an act of fixing information is correct, but in some ways that is the opposite of what I was looking for, because fixed information removes some of the time variance from the information. Even where one does not have the enormous reduction of information afforded by the regularity of a crystal structure, simply reducing the temperature of a system will reduce the amount of motion within the system, and so at least the description of the system over time will be more compact, since the system measured at a moment in time will have changed less when measured at a time shortly afterwards.
If one looks at how information is stored in computers, the silicon crystals are not used themselves to store information, but are a substrate (the carriers or space in which the information is held), and it is the electrical charges (which are themselves irregularities within the crystal structure) within the crystals that actually store information. The advantage of the crystal structure is that it can selectively fix or release the charges at selected times, thus providing a means by which one may control the information stored within the space of the crystals. It is only that which is irregular that can contain information, not that which is regular. The more regular an environment, the less information it contains. In order that silicon crystals be able to be used to manage the controlled storage of information, the need to be created with an extraordinary level of purity and regularity to ensure that any naturally embedded information (i.e. the irregularities within the structure) do not create noise in the desired information that we wish to place into the crystal framework.
As has been pointed out, we probably are using slightly different nomenclature, and I am willing to alter my nomenclature if you have one that better describes succinctly to you that which I am trying to describe.
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That's where you've got it wrong! Lets assume that the gas is monatomic. All the atoms are essentially identical and all you need to define is the temperature the number of atoms and the space it occupies the velocities and directions of the individual atoms are not needed (or measurable) to give as complete a desccription as it is possible to give. A whole array of individual small crystals requires a lot more information and whats more it holds it.
Learn, create, test and tell
evolution rules in all things
God says so!
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quote:
Originally posted by Soul Surfer
That's where you've got it wrong! Lets assume that the gas is monatomic. All the atoms are essentially identical and all you need to define is the temperature the number of atoms and the space it occupies the velocities and directions of the individual atoms are not needed (or measurable) to give as complete a desccription as it is possible to give. A whole array of individual small crystals requires a lot more information and whats more it holds it.
Learn, create, test and tell
evolution rules in all things
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OK, maybe I'm being totally stupid, but I don't see it.
If we take the simple notion of a monatomic gas confined within a box, yes, every atom of the gas will have the same local structure (within the atom itself), but each will have a different energy, and each atom of the gas can be absolutely anywhere within that box.
If you assume that all the atoms in a gas are identical, you are making an approximation about the bulk behaviour of the gas, but you are actually totally ignorant of where each atom is, or what its momentum or energy is.
If all of the gas has condensed into a single crystal, then even if that crystal is above zero kelvin, because each atom is bound within the crystal lattice, the range of position and energy values that the atom can have is very much smaller (i.e. there is very much greater predictability in where you will find each atom, and a more stringent upper limit to the momentum the atom may have, and so the amount of information you can obtain about its location and momentum that you could not have predicted by knowing the wider context is much less).
I understand what you are saying that assuming a single regular and perfect crystal is a simplification, and in the real world, the gas might condense into a number of separate and irregular and flawed crystals, and each of these flaws, irregularities, and separations, will all add to the information content, but one only needs to take into account the degree to which they deviate from the ideal. Ofcourse, in the extreme, the gas might condense into an amorphous solid state, where there are no crystals (crudely equivalent to each atom being a separate monatomic crystal), and in effect each atom is then just as unpredictable as if it was still in a gas state (except that, being bound into a solid, that range of values for momentum are more constrained than in a free moving gas).
I understand what you are saying about a solid (whether crystalline or amorphous) has a memory that is lacking in a gas, and so contains more information about the past, but it contains less information about the present.
Looking at some of the wikipedia pages on information theory (although I still get lost in some of the mathematical nomenclature), I think the phrase I am looking for is the a gas has more 'information entropy' than a crystal, because it has more randomness. I hope this clarifies our differences, or do you still believe that I am under some misapprehension somewhere?
http://en.wikipedia.org/wiki/Information_entropy
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The basic concept of entropy in information theory has to do with how much randomness there is in a signal or random event. An alternative way to look at this is to talk about how much information is carried by the signal.
As an example consider some English text, encoded as a string of letters, spaces and punctuation (so our signal is a string of characters). Since some characters are not very likely (e.g. 'z') while others are very common (e.g. 'e') the string of characters is not really as random as it might be. On the other hand, since we cannot predict what the next character will be, it does have some 'randomness'. Entropy is a measure of this randomness, suggested by Claude E. Shannon in his 1948 paper A Mathematical Theory of Communication.
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This is where you've got it wrong. information is related to the number of actual or potential distinct states that you can detect in a chunk of material. A volume containig a gas is a volume containing a gas and nothing else. You cannot identify the individual atoms from each other unless they are in a different physical state just going a bit faster or slower or in a different direction isnt enough. The statistics of the kinetic theory of gasses describe it completerely. If the gas condensed into a load of cryastals these could be arranged in all sorts of different ways and so there are loads of easily distinguishable states that it can be in.
Learn, create, test and tell
evolution rules in all things
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quote:
Originally posted by Soul Surfer
This is where you've got it wrong. information is related to the number of actual or potential distinct states that you can detect in a chunk of material. A volume containig a gas is a volume containing a gas and nothing else. You cannot identify the individual atoms from each other unless they are in a different physical state just going a bit faster or slower or in a different direction isnt enough. The statistics of the kinetic theory of gasses describe it completerely. If the gas condensed into a load of cryastals these could be arranged in all sorts of different ways and so there are loads of easily distinguishable states that it can be in.
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http://en.wikipedia.org/wiki/Kinetic_theory_of_gases
quote:
Postulates
The fundamental aspects of kinetic theory are given by several postulates:
- Gases are composed of molecules in constant, random motion; the moving particles constantly collide with each other and with the walls of the container containing the gas
- The collisions between gas molecules are elastic
- The collisions of gas particles with the walls of the container holding them are perfectly elastic as well
- The total volume of the gas molecules is negligible compared to the volume of the entire container. This is equivalent to stating that the distance separating the gas particles is relatively large compared to their size.
- The interactions between molecules are negligible
- The gas consists of very small particles, each of which has a mass
- The gas particles are constantly moving rapidly in a random fashion
- The average kinetic energy of a gas particle depends only on the temperature at which the gas particle is present
- The gas particles exert no force on one another
The above postulates accurately describe the behavior of ideal gases. Real gases approach ideality under conditions of low density and high temperature.
The theory deals with idealised gases, not real gases. It approximates well to real gases in many situations, but it would be wrong to suggest that “the kinetic theory of gasses describe it completely “. One particular aspect of gases it does not address is viscosity.
I accept your point that “information is related to the number of actual or potential distinct states that you can detect in a chunk of material “, and that in practical terms we cannot measure each molecule within a gas, but is this a theoretical limit or merely a technical limit at this time? There are certain theoretical limits in the amount of information one can measure at a quantum level (no matter what the technology), but I am not aware that there is any theoretical limit that precludes the discrimination between individual atoms or molecules within a gas, merely practical limits of our technology?
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Hisenberg uncertainty defines both how accurately you can measure things and how much you disturb a system by measuring it.
Consider a gas in a small box at room temperature. You may be able to measure the velocities and directions of individual atoms by watching the brownian motion of a single colloidal particle suspended in it using light. You may even be able to measure most of the infra red photons being emitted as a result of the atoms of gas bouncing off each other but you most certainly could not ever identify one atom individually and track its path through the gas let alone all of them. If this gas was condensed on to a solid surface it is possible to detect and manipulate atoms individually on this surface using an atomic force microscope (IBM have demonstrated this some years ago using xenon atoms).
Lat me try to put it in a different way. cooling things down enables complexity to develop. OK it may be stable and relatively immobile like crystals in a lump of granite but these crystals hold the information on what the conditions were like when they were formed when they were formed and even information about what has happened to this lump of granite since it was formed. A gas is a gas it has no memory and is stuck in a perpetual now that doesn't change much unless the temeperature changes.
I hope that I have finally convinced you gases are simple, condensed matter is much much more complex This is not just my opinion but the general opinion of the scientific community.
Learn, create, test and tell
evolution rules in all things
God says so!
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How a priori is the notion that cosmic evolution cumulatively could result in so called "dead-matter" (as in the case of these new quantum robots) finally reestablishing themself as the final step by way of producing "living matter" (humans) capable of forming such "intelligent machines" that could far out perform their creators--humans?
DocN
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quote:
Originally posted by Soul Surfer
Hisenberg uncertainty defines both how accurately you can measure things and how much you disturb a system by measuring it.
Indeed, but I assumed this would not have a very noticeable effect at the atomic level.
My understanding is that the precision to which you can measure a particle is related to its wavelength, and a whole atom, being a fairly massive object, would have a relatively short wavelength, and thus would be able to be measured with relatively high precision.
Am I wrong in this interpretation?
quote:
Consider a gas in a small box at room temperature. You may be able to measure the velocities and directions of individual atoms by watching the brownian motion of a single colloidal particle suspended in it using light. You may even be able to measure most of the infra red photons being emitted as a result of the atoms of gas bouncing off each other but you most certainly could not ever identify one atom individually and track its path through the gas let alone all of them.
The difference between measuring one atom, or all of the atoms, to my mind seems to be more a matter of instrumentation and computational power. If one can theoretically measure one atom, then one can theoretically (if not necessarily practically) measure one million atoms, or one billion atoms, or one mole of atoms.
Could one not (subject to limitations on instrumentation and computational power) perform the following experiment.
In a small box, place an ionised gas at very low pressure (but at high energy, using very heavy atoms, such as uranium gas) such that the mean free path of the atoms will be greater than the size of the box, and such that the number of atoms hitting any given area of the walls of the box would be a manageable number.
Etch into the side of the box a closely spaced grid of sensors that will detect if an (ionised) atom hits the side of the box near the sensor. The intent is that the low density of the gas, combined with the close spacing of the grid, will mean that in the vast majority of occasions only a single atom will hit the side of the box within any single cell of the grid, that cell being surrounded by 4 or more sensors that will detect the position and velocity of the ion. Ofcourse, the sensors will inevitably absorb a little of the kinetic energy of the ions, but if the ions are of sufficient energy, and the sensors sufficiently sensitive, this need not be an excessive amount, albeit any absorption of energy will inevitably limit precision.
Then by measuring the points of impact, and the velocity and direction of impact, one could extrapolate the flight path of the atoms between the impacts with the walls of the box.
Although the mean free path will be larger than the size of the box, so the number of inter-atomic collisions will be small, but clearly there will be times when an atom does not arrive at a wall as expected (from its departure at it last known point of impact), and then one has to compute the likely collisions that might have caused the change of flight path.
Would such a system theoretically be able to model the movement of ions in a low density gas?
Would Heisenberg's uncertainty pose significant limits on the precision of such a system (clearly, Heisenberg's uncertainty places limits even on the measurements of the flight path of a tennis ball, but those limits are minuscule in comparison to the scale of measurement one is taking)?
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If this gas was condensed on to a solid surface it is possible to detect and manipulate atoms individually on this surface using an atomic force microscope (IBM have demonstrated this some years ago using xenon atoms).
Lat me try to put it in a different way. cooling things down enables complexity to develop. OK it may be stable and relatively immobile like crystals in a lump of granite but these crystals hold the information on what the conditions were like when they were formed when they were formed and even information about what has happened to this lump of granite since it was formed. A gas is a gas it has no memory and is stuck in a perpetual now that doesn't change much unless the temeperature changes.
I hope that I have finally convinced you gases are simple, condensed matter is much much more complex This is not just my opinion but the general opinion of the scientific community.
As you say, there are various tools (tunnelling electron microscope, and atomic force microscope) that can measure the discrete positions of each atom in a crystal. OK, these tools cannot measure velocity, so there will be no applicable Heisenberg limit; but on the other hand the inter atomic distances in gas are so much larger, and yet you seem to be saying that individual atoms cannot be measured in a gas?
I accept, and always have done, that the information contained in a a gas is only of the moment (not sure about the phrase 'perpetual now', since the very nature of now is its transience – but that I think is just semantics).
Where I still have a problem is that in the experiment I suggested above for measuring the atoms in a sparse gas would have problems, not least with the inordinate amount of computing power that would have to be used to keep track of all the atoms. Yet mapping the atoms within a crystal is well within the capacity of our current computing capabilities. That alone would indicate to me that a crystal is a far simpler system than a gas. Am I wrong in believing that the computing power needed to map the atoms in a gas is far greater than the computing power required to map the atoms in a crystal?
I accept your point about the complexity of the bulk material, but this does not to my mind translate to the relative complexities at the atomic levels.
I also accept that this discussion has been about gases and crystals, but gets a lot more complex when one starts looking at liquids. A liquid lacks the symmetry of the crystal that allows a massive reduction in computing power to model it, but it has a far more complex inter-atomic interactions than the gaseous form.
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Sorry but you are still thinking the wrong way and I can't think of any more convincing arguments at the moment.
Your suggested experiment just indicates more clearly the impossibility and futility of mesuring the motions of individual atoms in a gas or liquid because the knowledge of either of them would not produce any different results from the statistics of the kinetic theory when augamented by a few other corrections like Van der walls forces that allow viscosity to be estimated.
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