Newsgroup: it.arti.fotografia
Titolo: [Fotopride] Mooolto lungo : lettura per il prossimo tema...

"  I will take a simple example. Suppose we have blue water, with ink, and
   white water, that is without ink, in a tank, with a little separation, and
   then we pull out the separation very delicately. The water starts to
   separate, blue on one side and white on the other side. Wait a while.
   Gradually the blue mixes up with the white, and after a while the water is
   ?luke blue?, I mean it is sort of fifty-fifty, the color uniformly
   distributed throughout. Now if we wait and watch this for a long time, it
   does not by itself separate...
   That gives us some clue. Let us look at the molecules. Suppose that we take
   a moving picture of the blue and white water mixing. It will look funny when
   we run it backwards, because we will start with uniform water and gradually
   the thing will separate -- it will be obviously nutty. Now we magnify the
   picture, so that every physicist can watch, atom by atom, to find out what
   happens irreversibly -- where the laws of balance of forward and backward
   break down. So you start, and you look at the picture. You have atoms of two
   different kinds (it?s ridiculous, but let?s call them blue and white)
   jiggling all the time in thermal motion. If we were to start at the
   beginning, we should have mostly atoms of one kind on one side, and atoms of
   the other kind on the other side. Now these atoms are jiggling around,
   billions and billions of them, and if we start them with one kind all on one
   side, and the other kind on the other side, we see that in their perpetual
   irregular motions they will get mixed up, and that is why the water becomes
   more or less uniformly blue.
   Let us watch any one collision selected from that picture, and in the moving
   picture the atoms come together this way and bounce off that way. Now run
   that section of the film backwards, and you find the pair of atoms moving
   together the other way and bouncing off this way. And the physicist looks
   with his keen eye, and measures everything, and says, ?That?s all right,
   that?s according to the laws of physics. If two molecules came together this
   way, they would bounce off this way?. It is reversible. The laws of molecular
   collision are reversible.
   So if you watch too carefully you cannot understand it at all, because every
   one of the collisions is absolutely reversible, and yet the whole moving
   picture shows something absurd, which is that in the reversed picture the
   molecules start in the reversed condition -- blue, white, blue, white, blue,
   white -- and as time goes on, through all the collisions, the blue separates
   from the white. But they cannot do that -- it is not natural that the
   accidents of life should be such that the blues will separate themselves
   from the whites. And yet if you watch this reversed movie very carefully
   every collision is okay.
   Well you see that all there is to it is that the irreversibility is caused
   by the general accidents of life. If you start with a thing that is
   separated and make irregular changes, it does get more uniform. But if it
   starts uniform and you make irregular changes, it does not get separated. It
   could get separated. It is not against the laws of physics that the
   molecules bounce around so that they separate. It is just unlikely. It would
   never happen in a million years. And that is the answer. Things are
   irreversible only in a sense that going one way is likely, and going the
   other way, although it is possible and is according to the laws of physics,
   would not happen in a million years. It is just ridiculous to expect that if
   you sit there long enough the jiggling of the atoms will separate a uniform
   mixture of ink and water into ink on one side and water on the other...
   And so the apparent irreversibility of nature does not come from the
   irreversibility of the fundamental physical laws; it comes from the
   characteristic that if you start with an ordered system, and have the
   irregularities of nature, the bouncing of molecules, then the thing goes one
   way. (pp.105-107)
   ...I do not know if you have ever had the experience -- I have -- of sitting
   on the beach with several towels, and suddenly a tremendous downpour comes.
   You pick up the towels as quickly as you can, and run into the bathhouse.
   Then you start to dry yourself, and you find that this towel is a little
   wet, but it is drier than you are. You keep drying with this one until you
   find that it is too wet -- it is wetting you as much as drying you -- and
   you try another one; and pretty soon you discover a horrible thing -- that
   all the towels are damp and so are you. There is no way to get any drier,
   even though you have many towels, because there is no difference in some
   sense between the wetness of the towels and the wetness of yourself. I could
   invent a kind of quantity which I could call ?ease of removing water?. The
   towel has the same ease of removing water from it as you have, so when you
   touch yourself with the towel, as much water comes off the towel on to you
   as comes from you to the towel. It does no mean there is the same amount of
   water in the towel as there is on you -- a big towel will have more water in
   it than a little towel, but they have the same dampness. When things get to
   the same dampness then there is nothing you can do any longer.
   Now the water is like the energy, because the total amount of water is not
   changing. (If the bathhouse door is open and you can run into the sun and
   get dried out, or find another towel, then you?re saved, but suppose
   everything is closed, and you can?t get away from these towels or get any
   new towels.) In the same way if you imagine a part of the world that is
   closed, and wait long enough, in the accidents of the world the energy, like
   the water, will be distributed over all the parts evenly until there is
   nothing left of one-way-ness, nothing left of the real interest of the world
   as we experience it...
   Incidentally, the thing that corresponds to the dampness or the ?ease of
   removing water? is called temperature, and although I say when two things
   are at the same temperature they get balanced, it does not mean they have
   the same energy in them; it means that it is just as easy to pick energy off
   one as to pick it off the other. Temperature is like ?ease of removing
   energy?. So if you sit them next to each other, nothing apparently happens;
   they pass energy back and forth equally, but the net result is nothing. So
   when things have become all of the same temperature, there is no more energy
   available to do anything. The principle of irreversibility is that if things
   are at different temperatures and are left to themselves, as time goes on
   they become more and more at the same temperature, and the availability of
   energy is perpetually decreasing.
   This is another name for what is called the entropy law, which says the
   entropy is always increasing. But never mind the words; stated the other
   way, the availability of energy is always decreasing. And that is a
   characteristic of the world, in the sense that it is due to the chaos of
   irregular molecular motions. Things of different temperature, if left to
   themselves, tend to become the same temperature. If you have two things at
   the same temperature, like water on an ordinary stove without a fire under
   it, the water is not going to freeze and the stove get hot. But if you have
   a hot stove with ice, it goes the other way. So the one-way-ness is always
   to the loss of the availability of energy."
							R. P. Feynman
|~~~~~~|
|(O>   |\  Fabio Cavaliere (Homebrew apprentice & GLUG member)
|//\   | | "I play dead - and the hurt stops" (Bjork)
|V_/_  | | e-mail > 
cava...@server1.fisica.unige.it
|######|-  GLUG on the Web : 
http://genova.linux.it
+------+

 .......
     [megaCUT]
ma lo scappellamento a destra o a sinistra?
:-)
GG
--------------------------------
Inviato via 
http://usenet.libero.it

 R. P. Feynman
Occhéi, ritiro la mia candidatura a giudice. 
Alla prossima entropata verbolabile, ritiro anche l'hosting...

Un'ottima foto esemplificativa invece del concetto di degrado della qualità
dell'energia sarebbe quella classica del particolare dei dischi in carbonio
di una F1 in staccata.
Frenando surriscaldi i dischi, ma puoi riscaldare i dischi dei freni quanto
vuoi che la macchina mica si muove :-)
A.A.I.
------------------------------------------------------------
Antonio Taccone | Siamo scienziati, non ingegneri!
ata...@tin.it
     | A. A. Bertossi, 1990 - Durante una lezione
                           | Università di Pisa - Dipartimento di
Informatica

 white water, .... cut-issimo!!
Ma che birra ti sei bevuto questa volta??????????????????????
Lo Strano
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Venia, pieta' ! "Reeeesta con nooooi...nuuuun ce lassssa'...."


> Una threcher ! Cheddomande...
Pensavo una Piscemberger! ;) (calda dicono che sia buonissima!)

Ma la foto la vuoi prima, durante, nel mentre, nel divenire, dell'essere,
con la grana gia' messcolata o con la grana ttta a dx, con la grana tutta
asx.....? eh?
N
PS : se non si capisce sono arrivato solo fino ai 3/4 poi ho ceduto,
sigh...!
N

Ragazzi cambiate pusher!!!!
--
                 - L' APACHE -
 
http://digilander.libero.it/mauriziotoni
  *****************************

>>Ragazzi cambiate pusher!!!!
....costa poco....
:PPPPPP
N

Se surriscaldi le palle di qualcuno invece... egli si muove, giusto?
--
Nizoo
Web Page: 
http://digilander.iol.it/nizoo
 
http://www.nizoo.it
"Zott !!!" <zottw...@virgilio.it.levalo> ha scritto nel messaggio
news:9447a.237852$0v.66...@news1.tin.it...


 Informatica
Dimmi che hai davvero sentito Bertossi con le tue orecchie mentre
pronunciava queste parole ... MI TI CO! :-)
Potere alla Scienza!
Bye
Carmine

 "  I will take a simple example. Suppose we have blue water, with ink, and
bla bla bla...
letto tutto, che ho vinto?
saluti isoentropici
giuseppe

 Alla prossima entropata verbolabile, ritiro anche l'hosting...
Non conosci Richard Feynman...
--
Phil O'Sophy || Filippo M. Caroti
www.filippocaroti.com
phi...@libero.it
______________________________________________________
"At my sign unleash the hell."                 (Maximus Decimus Meridius)
______________________________________________________
"Suonavo il piano nel bar di Rusty da quattro mesi o giů di lě, quando
incontrai Rima Marshall.
Entrň nel bar una sera di temporale, con la pioggia che batteva sul tetto
di metallo e il tuono che rombava in lontananza."              (J.H.Chase)
______________________________________________________
Cast a cold eye
on life, on death.
Horseman pass by.                                   (tombstone of W.B.Yeats)
______________________________________________________
Alě, boma yé... Alě, boma yé...  (100.000 people in Kinshasa stadium)
______________________________________________________

 Non conosci Richard Feynman...
In effetti, agnosco

 Potere alla Scienza!
Confermo. E non sono il solo di quel corso ad avere questa frase in
signature, ha fatto epoca erano gli ultimi anni del boletus marzottiferus...
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più che quotidianamente compio esperimenti di miscelazione dei gas.
E sempre scopro  che che in effetti si miscelano.
Daltronde sono ancora vivo, se le mie scureggie rimanessero in
prossimità della zona di eiezione, probabilmente sarei già
morto da tempo....
invece, fortunatamente, si espandono raggiungendo le
nari chi mi sa a fianco. Gioia e giubilo! l'entropia è aumentata.
Ma pultroppo, o per fortuna, il mio ufficio non è un sistema chiuso
dopo qualche tempo la concentrazione di gas intestinali diventa così
bassa che scende sotto la soglia di percettibilità umana.
Sono sicuro che il cane che stà di sotto in cortile invece ha una soglia
più bassa, non si vuole fare mai accarezzare da me.
----
ciao
aXSe
http://www.meta.is.it/alberi/
 

 morto da tempo....
perche'? sei un fumatore?
quella che si dice autocombustione...
--
bobo
http://digilander.libero.it/bobowashere

 Una threcher ! Cheddomande...
ogni tanto ripenso al tipo che aveva "invaso" iaf e che ci degno'
graziosamente di segnalare la fine delle ostilita' con un apposito post...
dove sara' ora? l'avranno gia' paracadutato su Baghdad?
--
bobo
http://digilander.libero.it/bobowashere