Is World Year of Physics ended ?

Ariane Von WolfLand
Ariane Von WolfLand
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The earth atmosphere is a


The earth atmosphere is a gamma ray detector and can discover the first "black holes". The encounter of a quantum of gamma ray bearing huge energy with the atmosphere's atoms, creates pairs of electrons and positrons (anti-electrons) which, after encountering other atoms, make appear pairs of new electrons and positrons , and so an electron current is created. The outcome is a sort of light called "Cerenkov radiation". So we can , by detecting rays of light at night sky, search for gamma ray explosions.

If actually the chaos and irregularities prevailed in primordial world, we can expect that the number of black holes are much more than what our observation of gamma ray shows.

Anyway and on the other hand if we keep our distance from this sort of data, many questions could touch our mind. Which part of what we can perceive is really "real"(the concept of "real" we understand usually)? What we imagine about the causality of events in cosmos , is not a kind of huge and continual illusion which veils the "truth" ? A strange and deep truth which is not some sort of matter but a "spirit" and an "Intelligence" ?

Ariane

Chipper Q
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Ariane, most interesting

Ariane, most interesting thread! I'm glad you mentioned positrons. It's my understanding that they can be expressed diagrammatically as electrons moving backwards in time. How does this relate to the discussion earlier in the thread about the arrow of time? Is it correct to say that this symmetry around the direction of time exists for every particle and its anti-particle?

Mike, I'm a bit confused by your comments - are we, or aren't we, breaking the laws of thermodynamics? What are the working definitions of order/disorder and simple/complex? I agree with the part of your post about there being a cost involved (energy-wise) when we do things like turning many grains of sand into a glass, but isn't the bottom line that energy is conserved? So how do we account for the existence of the glass, or a laser, or a computer? I don't see how these things would happen, if water only ever flowed its own way...

Mike Hewson
Mike Hewson
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RE: Mike, I'm a bit

Message 22930 in response to message 22929

Quote:
Mike, I'm a bit confused by your comments - are we, or aren't we, breaking the laws of thermodynamics?


No, we're not. Sorry, I was being rhetorical. :-)

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What are the working definitions of order/disorder


Fundamentally it's an ( objective ) number related to the counting of occupied quantum states, and this never decreases in an isolated system. Entropy is a measure of disorder.

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and simple/complex?


Whatever you want it to be. It's subjective. Order and simplicity are not always interchangeable words, although they may be for some situations. Same for disorder/complexity. There's an intersection here with information theory which can confuse. As an example, let us say I have ten ordinary playing cards of some one suit ( say Hearts ), numbered from 1 through to 10 ( no Kings, Queens or Jacks ). Suppose I shuffle and deal them out 'fairly' and get the exact sequence 1,2,3,4,5,6,7,8,9,10. Wow, you say! What are the odds of that etc... But what if I'd dealt the exact sequence 4,7,2,1,9,6,3,10,8,5? Would you be as excited/surprised? Well, you should be, because both sequences have exactly the same probability! Meaning that: if I repeat the shuffling/dealing a large number of times ( the more the better and may be a really big number ) the number of times each of the above sequences occur will steadily approach each other ( converge ). The first sequence is special to us because of ordering that makes it easy to specify by some 'simple' rule ( say: start at one, add one to get the next, and stop at ten ). The second sequence could no doubt be specified by some rule, offhand I don't know what, but clearly not as evident or as 'simple'. Now that 'fairly' adjective that I used above meant that the physical process which produces any given sequence was indifferent to any labelling of the cards. Hence given certain specified, reproducible, starting and ending states ( ie. ignoring the card labels ) all the sequences can be arranged to be thermodynamically equivalent ( in controlled conditions ) - yet they clearly have different 'information' content to us.
Now, if you're still with me, let's compare the 1,2,3,4,5,6,7,8,9,10 sequence versus any other sequence at all. Now the arrival of this 1...10 sequence looks really special, of low probability and wow! But those other sequences are in a vastly larger set, because we lumped them together that way.

Quote:
I agree with the part of your post about there being a cost involved (energy-wise) when we do things like turning many grains of sand into a glass, but isn't the bottom line that energy is conserved?


Yes it is, but that is only one constraint.
Another classic texbook example is a sealed box with a partition down the middle, initially some gas on one side and vacuum on the other. Remove the partition and shortly the gas will distribute all through the box ( by microscopically reversible collisions conserving energy ). But you'll be waiting quite a long time, probably never ( but maybe just until the next Big Crunch if there is one .. ), before the gas particles will all be on the original side of the box ( you can't rule it out ) - so you can put the partition back in leaving vacuum again on the other side! If you do the calculation of entropy ( not subjective simplicity ) it increases after the partition is removed compared to before.

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So how do we account for the existence of the glass, or a laser, or a computer?


Well, alot of thermodynamics can be analysed ( perhaps with difficulty ) by thinking as follows. You have a hot spot H, and a cold spot C. Hotter temperature means the average energy per particle is greater than the average energy per particle for the colder spot. If left alone ( H and C are isolated from the rest of the universe ) and in contact ( together ) energy will flow from H to C, and thus in time the temperature will become constant throughout at somewhere between the two original temperatures. So the hot place becomes cooler, and the cold place becomes hotter. However as part of this system there may be a mechanism for producing work during this equilibration. This work is essentially nett motion against a force. Classic example is the firebox of a steam engine ( the conceptual womb of thermodynamic theory ), which is the hot place, and the condensor where the steam becomes liquid water, which is the cold place. The work is produced where the hot steam expands and pushes the piston which makes the wheels go 'round and the train chug along to the next town... during which the states of the wood, water and all else involved ( dramatically ) increase the measure of their occupied quantum states. You can use this work, with matters suitably arranged, to make glass, lasers and computers!

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I don't see how these things would happen, if water only ever flowed its own way...


True, but it never gets to do that, does it? There is always interaction, and an isolated system is an unachievable abstraction, but with care can be closely approximated. On the plus side, careful thermodynamic thinking and modelling has yet to be contradicted by experiment, so like any good science remains falsifiable until some future counter-example is apparent.
Hope this helps, Mike. :-)

( edit ) In which case it is then becomes falsified and we have to adjust our thinking, limit it's applicability, or whatever....

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

gravywavy
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RE: IF evolution is simply

Message 22931 in response to message 22923

Quote:

IF evolution is simply the result of physical and chemical processes, they MUST obey the laws of thermodynamics, including of course the "dissipative structures" described by Prigogine and coworkers, that is modern thermodynamics. Cheers.

There are two answers to this.

The mainstream answer is that evolution is a local decrease in entropy at the expense of an even larger increase in entropy elsewhere. The law of increasing entropy only claims to be valid for a closed system, and living systems all import high grade energy (sunlight, food, etc) and export lower grade energy (body heat, 'not food', etc).

The dissident answer is to say that all systems tend towards stable equilibrium and this may or may not involve an increase in entropy. Everyone agrees that yes thermodynamic systems have as their stable configuration a low entropy state, all the matter thinly spread etc.

Dissidents would point out however that gravitational systems work differently - the most stable configuration is a clump or a spinning disk. If it turned out that evolution was not only a result of thermodynaic processes, those dissidents would say that the laws of thermodynamics did not apply.

~~gravywavy

Ariane Von WolfLand
Ariane Von WolfLand
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Nowadays we know that each


Nowadays we know that each particle has an anti-particle and these two can anihilate each-other.But given there is somehow a spontaneous smashing of symmetry, the number of particles around us is considerablely more than the anti-particles, This phenomenon has a virtual relation with the arrow of time. Until 1956 it was believed that the physics laws depend on three different symmetries C,P and T. In C symmetry the laws governing particles and anti-particles are the same. In P symmetry the laws governing each position and its reflection in the mirror are the same.In T symmetry by upside-downing the direction of motion of all particles and anti-particles, the system reaches its previous position. In other words, by moving along the direction of time or across it, the same laws govern.

But later, it has been demonstrated that the weak interaction doesn't follow the C symmetry,e.g. a world made up of anti-particles, would have a different behavior than ours. Although it seems that the weak interaction follows the mixed CP symmetry.

A mathematical theorem pretends that each theory following, at the same time, the quantum mechanic and the general relativity, should have the CPT symmetry, that means by replacing particles and anti-particles and reflecting all in a mirror and by upside-downing the arrow of time, the world should have an identical behavior. But it is not so because if only they don't upside-down the arrow of time, the world would not have the same behavior, because, not following the T symmetry , this would be a challenge against the physics laws...

Ariane

Mike Hewson
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RE: But later, it has been

Message 22933 in response to message 22932

Quote:
But later, it has been demonstrated that the weak interaction doesn't follow the C symmetry...


NO! P symmetry is violated by the weak force. It couples only to the 'left-handed' quarks and leptons.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

tullio
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RE: RE: IF evolution is

Message 22934 in response to message 22931

Quote:
Quote:

IF evolution is simply the result of physical and chemical processes, they MUST obey the laws of thermodynamics, including of course the "dissipative structures" described by Prigogine and coworkers, that is modern thermodynamics. Cheers.

.

The dissident answer is to say that all systems tend towards stable equilibrium and this may or may not involve an increase in entropy. Everyone agrees that yes thermodynamic systems have as their stable configuration a low entropy state, all the matter thinly spread etc.

Dissidents would point out however that gravitational systems work differently - the most stable configuration is a clump or a spinning disk. If it turned out that evolution was not only a result of thermodynaic processes, those dissidents would say that the laws of thermodynamics did not apply.


I always thought, on the basis of Boltzmann's equation, that a state of high entropy is stabler (more probable) than a state of low entropy, Am I wrong?
Tullio

MarkF
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The Weak theory violates P

The Weak theory violates P symmetry and neutral Kaon decay can violates C symmetry. In both cases CPT is always preserved.

MarkF
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RE: I always thought, on

Quote:
I always thought, on the basis of Boltzmann's equation, that a state of high entropy is stabler (more probable) than a state of low entropy, Am I wrong?


Not according to my understanding. But entropy is not the only thing that determines how a system will behave. For example a two moles Oxygen atoms will have more entropy the a mole of Oxygen molecules yet at atmospheric density you will almost always see only the later.

Chipper Q
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Thanks Mike, that helps quite

Thanks Mike, that helps quite a bit. So is the universe considered open or closed or isolated..? I understand it's flat, and possibly even just one of many in parallel, but ... how did the energy from the big bang get in? Is energy leaking out? When you mentioned everything occupying the lowest possible quantum state, would that then be like the pre-big bang singularity? What does 'increase the measure of their occupied quantum states' mean? Are more states occupied closer to the ground state, or does the measure of unoccupied states increase in quantity (in the steam engine example)?

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