Re: defining laws in isolation or 'no other force acting'
David Deutsch <david.deutsch-LR/[email protected]> Sun, 5 Jan 2014 18:44:33 +0000
| Newsgroups | gmane.science.physics.fabric-of-reality |
|---|---|
| Message-ID | <[email protected]> |
--Apple-Mail=_6698B766-FE59-4C6B-8E59-25714D5FF23D Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="windows-1252" On 15 Dec 2013, at 04:48, hibbsa-/[email protected] wrote: > Hi DD, hope you are we= ll, > Quoting from your CT paper > > "2.2 Constructor-independent laws of= physics > In physics, too, most laws are about substrates only: they hold = for all possible > constructors. But the prevailing conception disguises th= at. For example, one way of > formulating a conservation law in the prevail= ing conception is that for every isolated > physical system S, a certain qu= antity Q(S) never changes. But since an isolated > system never deviates fr= om a particular trajectory, almost all its attributes (namely, > all deviat= ions from that trajectory) remain unchanged, not just conserved quantities.= > For instance, the total energy of the atoms of an isolated crystal remai= ns unchanged, > but so does their arrangement, and only the former invarian= ce is due to a > conservation law. In constructor-theoretic terms, the arra= ngement could be changed > by a constructor while the energy could not. > M= ore generally, what makes the attributes that we call =91conserved quantiti= es=92 > significant is not that they cannot change when a system is isolate= d, but that they > cannot be changed, whether or not the system is isolated= , without depleting some > external resource." > > Reading this I'm curiou= s, DD, why in your judgement, assumptions about isolation, or 'no other for= ces acting' and so on, tend to be used when defining laws? > > They are u= sed when the laws are about isolated systems. We can't choose what the laws= we discover are going to say. > I think it's because that is the simplest,= by far clearest, way to be very clear what the law actually is. > It allow= s a statement like this "for any isolated physical system S, a certain quan= tity Q(s) remains constant" instead of much longer statements that have to = enail that energy or whatever, cannot be created or destroyed...but it can = seem to be but what's going on there is energy is being transported from so= mewhere else.... > > As in Newton's laws of motion with assumptions about = no other force acting...'. He wasn't saying that was the only time the law = was true. > > I appreciate this is a very marginal aspect of your CT work,= but I do think you are operating a misunderstanding here and the other ins= tances like perpetual motion etc. > Or perhaps I am....I shall look out for= what you have to say > In that sense, the laws of constructor theory *ar= e* about isolated systems: the substrate plus constructor. -- David Deutsc= h --Apple-Mail=_6698B766-FE59-4C6B-8E59-25714D5FF23D Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/htm= l4/strict.dtd"> <html> <head> </head> <body style=3D"background-color: #fff;"> <span style=3D"display:none"> </span> <!--~-|**|PrettyHtmlStartT|**|-~--> <div id=3D"ygrp-mlmsg" style=3D"position:relative;"> <div id=3D"ygrp-msg" style=3D"z-index: 1;"> <!--~-|**|PrettyHtmlEndT|**|-~--> <div id=3D"ygrp-text" > =20=20=20=20=20=20 =20=20=20=20=20=20 <p>On 15 Dec 2013, at 04:48, <a href=3D"mailto:hibbsa-/[email protected]">hibb= sa-/[email protected]</a> wrote:<br><div><br class=3D"Apple-interchange-newline"><bl= ockquote type=3D"cite"><div style=3D"font-family: Monaco;font-size: 14px;fo= nt-style: normal;font-variant: normal;font-weight: normal;letter-spacing: n= ormal;text-align: start;text-indent: 0px;text-transform: none;white-space: = normal;">Hi DD, hope you are well, <p>Quoting from your CT paper</p><p= >"2.2 Constructor-independent laws of physics<br>In physics, too, most laws= are about substrates only: they hold for all possible<br>constructors. But= the prevailing conception disguises that. For example, one way of<br>formu= lating a conservation law in the prevailing conception is that for every is= olated<br>physical system S, a certain quantity Q(S) never changes. But sin= ce an isolated<br>system never deviates from a particular trajectory, almos= t all its attributes (namely,<br>all deviations from that trajectory) remai= n unchanged, not just conserved quantities.<br>For instance, the total ener= gy of the atoms of an isolated crystal remains unchanged,<br>but so does th= eir arrangement, and only the former invariance is due to a<br>conservation= law. In constructor-theoretic terms, the arrangement could be changed<br>b= y a constructor while the energy could not.<br>More generally, what makes t= he attributes that we call =91conserved quantities=92<br>significant is not= that they cannot change when a system is isolated, but that they<br>cannot= be changed, whether or not the system is isolated, without depleting some<= br>external resource."</p><p>Reading this I'm curious, DD, why in your judg= ement, assumptions about isolation, or 'no other forces acting' and so on, = tend to be used when defining laws?</p><div><br></div></div></blockquote>Th= ey are used when the laws are about isolated systems. We can't choose what = the laws we discover are going to say.<br><blockquote type=3D"cite"><div st= yle=3D"font-family: Monaco;font-size: 14px;font-style: normal;font-variant:= normal;font-weight: normal;letter-spacing: normal;text-align: start;text-i= ndent: 0px;text-transform: none;white-space: normal;"><div>I think it's bec= ause that is the simplest, by far clearest, way to be very clear what the l= aw actually is.</div><p>It allows a statement like this "for any isolated p= hysical system S, a certain quantity Q(s) remains constant" instead of much= longer statements that have to enail that energy or whatever, cannot be cr= eated or destroyed...but it can seem to be but what's going on there i= s energy is being transported from somewhere else....</p><p>As in Newton's = laws of motion with assumptions about no other force acting...'. He wasn't = saying that was the only time the law was true.</p><div>I appreciate this i= s a very marginal aspect of your CT work, but I do think you are operating = a misunderstanding here and the other instances like perpetual motion etc.<= /div><p>Or perhaps I am....I shall look out for what you have to say</= p></div></blockquote><br></div><div>In that sense, the laws of constructor = theory *are* about isolated systems: the substrate plus constructor.</div><= div><br></div><div>-- David Deutsch</div><br></p> </div> =20=20=20=20=20 <!--~-|**|PrettyHtmlStart|**|-~--> <div style=3D"color: #fff; height: 0;">__._,_.___</div> =20=20=20=20=20=20=20=20=20=20 =20=20 =20=20=20=20 <table cellspacing=3D4px style=3D"margin-top: 20px; margin-bottom: 10px= ;"> <tbody> <tr> <td style=3D"font-size: 12px; font-family: arial; font-weight: bo= ld; padding: 7px 5px 5px; color: #FFF; background-color: #F2F2F2; border: 1= px solid #EAEAEA " > <a style=3D"text-decoration: none; color: #2D50FD= " href=3D"http://groups.yahoo.com/group/Fabric-of-Reality/post;_ylc=3DX3oDM= TJxaHV1ZDFkBF9TAzk3MzU5NzE0BGdycElkAzE4ODg2MDAEZ3Jwc3BJZAMxNzA1MDIwNTg1BG1z= Z0lkAzI1NjA5BHNlYwNmdHIEc2xrA3JwbHkEc3RpbWUDMTM4ODk0ODYxNA--?act=3Dreply&me= ssageNum=3D25609">Reply via web post</a> </td> <td style=3D"font-size: 12px; font-family: arial; padding: 7px 5p= x 5px; color: #FFF; background-color: #F2F2F2; border: 1px solid #EAEAEA; "= > <a href=3D"mailto:David.Deutsch-LR/[email protected]?subject=3DRe%3A%20def= ining%20laws%20in%20isolation%20or%20%26%2339%3Bno%20other%20force%20acting= %26%2339%3B" style=3D"text-decoration: none; color: #2D50FD;"> Reply to sender </a>=20 </td> <td style=3D"font-size: 12px; font-family: arial; padding: 7px 5p= x 5px; color: #FFF; background-color: #F2F2F2; border: 1px solid #EAEAEA; "= > <a href=3D"mailto:[email protected]?subject=3DR= e%3A%20defining%20laws%20in%20isolation%20or%20%26%2339%3Bno%20other%20forc= e%20acting%26%2339%3B" style=3D"text-decoration: none; color: #2D50FD"> Reply to group </a>=20 </td> <td style=3D"font-size: 12px; font-family: arial; padding: 7px 5p= x 5px; color: #FFF; background-color: #F2F2F2; border: 1px solid #EAEAEA; "= > <a href=3D"http://groups.yahoo.com/group/Fabric-of-Reality/post= ;_ylc=3DX3oDMTJlYmZwOXVkBF9TAzk3MzU5NzE0BGdycElkAzE4ODg2MDAEZ3Jwc3BJZAMxNzA= 1MDIwNTg1BHNlYwNmdHIEc2xrA250cGMEc3RpbWUDMTM4ODk0ODYxNA--" style=3D"text-de= coration: none; color: #2D50FD">Start a New Topic</a> </td> <td style=3D"font-size: 12px; font-family: arial; padding: 7px 5p= x 5px; color: #2D50FD; background-color: #F2F2F2; border: 1px solid #EAEAEA= ; " > <a href=3D"http://groups.yahoo.com/group/Fabric= -of-Reality/message/25606;_ylc=3DX3oDMTM2OGttOTR2BF9TAzk3MzU5NzE0BGdycElkAz= E4ODg2MDAEZ3Jwc3BJZAMxNzA1MDIwNTg1BG1zZ0lkAzI1NjA5BHNlYwNmdHIEc2xrA3Z0cGMEc= 3RpbWUDMTM4ODk0ODYxNAR0cGNJZAMyNTYwNg--" style=3D"text-decoration: none; co= lor: #2D50FD;">Messages in this topic</a> (2) </td> </tr> </tbody> </table> =20=20=20=20=20=20=20=20 <!------- Start Nav Bar ------> <!-- |**|begin egp html banner|**| --> <div id=3D"ygrp-vital" style=3D"background-color: #f2f2f2; font-family: Ver= dana; font-size: 10px; margin-bottom: 10px; padding: 10px;"> <span id=3D"vithd" style=3D"font-weight: bold; color: #333; text-tran= sform: uppercase; ">Recent Activity:</span> <ul style=3D"list-style-type: none; margin: 0; padding: 0; display: inl= ine;"> </ul> =20=20=20=20 <div style=3D"clear: both; padding-top: 2px; color: #1e66ae;"> <a href=3D"http://groups.yahoo.com/group/Fabric-of-Reality;_ylc=3DX3oDM= TJlMmwzamplBF9TAzk3MzU5NzE0BGdycElkAzE4ODg2MDAEZ3Jwc3BJZAMxNzA1MDIwNTg1BHNl= YwN2dGwEc2xrA3ZnaHAEc3RpbWUDMTM4ODk0ODYxNA--" style=3D"text-decoration: non= e;">Visit Your Group</a> </div> </div> =20=20 <div id=3D"ft" style=3D"font-family: Arial; font-size: 11px; margin-top: 5p= x; padding: 0 2px 0 0; clear: both;"> <a href=3D"http://groups.yahoo.com/;_ylc=3DX3oDMTJkM3BtZXU5BF9TAzk3NDc2NT= kwBGdycElkAzE4ODg2MDAEZ3Jwc3BJZAMxNzA1MDIwNTg1BHNlYwNmdHIEc2xrA2dmcARzdGltZ= QMxMzg4OTQ4NjE0" style=3D"float: left;"><img src=3D"http://l.yimg.com/ru/st= atic/images/yg/img/email/new_logo/logo-groups-137x15.png" height=3D"15" wid= th=3D"137" alt=3D"Yahoo! 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