Re: defining laws in isolation or 'no other force acting'
Gary Oberbrunner <[email protected]> Mon, 6 Jan 2014 09:00:18 -0500
| Newsgroups | gmane.science.physics.fabric-of-reality |
|---|---|
| Message-ID | <CAFChFyh6rfm2a6vjN9-CCgwwdQViVrV2Ozvb08d+zDFa5CxtcQ@mail.gmail.com> |
--ieg59StBxogjT1fps53QPmNPvB9MXQNVajNmf9N Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit On Mon, Jan 6, 2014 at 7:23 AM, <hibbsa-/[email protected]> wrote: > > > ---In [email protected], <david.deutsch@...> wrote: > ... >>> In that sense, the laws of constructor theory *are* about isolated systems: the substrate plus constructor. >> >> The isolated system doubles as a better way to make clear there aren't other influences acting. Certainly there are applications where the boundary has independent value....say in how the major problems of mechanical engineering were solved (which were fundamental in nature) >> >> But, take Newton's laws of motion. Say, an object will remain at rest or continue the way its going at constant velocity, WHEN no other forces are acting. >> >> Does that say that when forces are acting, inertia and the other laws aren't also acting? No one would say that. Newton uses forces acting and that law in combination to get orbital behaviour, show conservation of momentum hence explain elliptical orbit and so on. > > You just draw the line in a different place in that case. The object undergoing the force, as well as the object(s) exerting the force. But you exclude all the irrelevant stuff like what's going on on Pluto. As usual, the math tells the story more succinctly: f=ma. This is _always_ true, and covers both of your cases above. Sometimes, like in electromagnetism, you have to use a surface integral around the boundary of the system of interest (to enumerate the flux in/out of the system for instance). -- Gary --ieg59StBxogjT1fps53QPmNPvB9MXQNVajNmf9N Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> </head> <body style="background-color: #fff;"> <span style="display:none"> </span> <!--~-|**|PrettyHtmlStartT|**|-~--> <div id="ygrp-mlmsg" style="position:relative;"> <div id="ygrp-msg" style="z-index: 1;"> <!--~-|**|PrettyHtmlEndT|**|-~--> <div id="ygrp-text" > <p>On Mon, Jan 6, 2014 at 7:23 AM, <hibbsa-/[email protected]> wrote:<br> <br> ><br> ><br> > ---In [email protected], <david.deutsch@...> wrote:<br> > ...<br> >>> In that sense, the laws of constructor theory *are* about isolated systems: the substrate plus constructor.<br> >><br> >> The isolated system doubles as a better way to make clear there aren't other influences acting. Certainly there are applications where the boundary has independent value....say in how the major problems of mechanical engineering were solved (which were fundamental in nature)<br> >><br> >> But, take Newton's laws of motion. Say, an object will remain at rest or continue the way its going at constant velocity, WHEN no other forces are acting.<br> >><br> >> Does that say that when forces are acting, inertia and the other laws aren't also acting? No one would say that. Newton uses forces acting and that law in combination to get orbital behaviour, show conservation of momentum hence explain elliptical orbit and so on.<br> ><br> > You just draw the line in a different place in that case. The object undergoing the force, as well as the object(s) exerting the force. But you exclude all the irrelevant stuff like what's going on on Pluto. As usual, the math tells the story more succinctly: f=ma. This is _always_ true, and covers both of your cases above.<br> <br> Sometimes, like in electromagnetism, you have to use a surface integral around the boundary of the system of interest (to enumerate the flux in/out of the system for instance).<br> <br> -- <br> Gary<br> <br> </p> </div> <!--~-|**|PrettyHtmlStart|**|-~--> <div style="color: #fff; height: 0;">__._,_.___</div> <table cellspacing=4px style="margin-top: 20px; margin-bottom: 10px;"> <tbody> <tr> <td style="font-size: 12px; font-family: arial; font-weight: bold; padding: 7px 5px 5px; color: #FFF; background-color: #F2F2F2; border: 1px solid #EAEAEA " > <a style="text-decoration: none; color: #2D50FD" href="http://groups.yahoo.com/group/Fabric-of-Reality/post;_ylc=X3oDMTJxZmgxZjhxBF9TAzk3MzU5NzE0BGdycElkAzE4ODg2MDAEZ3Jwc3BJZAMxNzA1MDIwNTg1BG1zZ0lkAzI1NjEzBHNlYwNmdHIEc2xrA3JwbHkEc3RpbWUDMTM4OTAxODQ2OQ--?act=reply&messageNum=25613">Reply via web post</a> </td> <td style="font-size: 12px; font-family: arial; padding: 7px 5px 5px; color: #FFF; background-color: #F2F2F2; border: 1px solid #EAEAEA; " > <a href="mailto:[email protected]?subject=Re%3A%20defining%20laws%20in%20isolation%20or%20%27no%20other%20force%20acting%27" style="text-decoration: none; color: #2D50FD;"> Reply to sender </a> </td> <td style="font-size: 12px; font-family: arial; padding: 7px 5px 5px; color: #FFF; background-color: #F2F2F2; border: 1px solid #EAEAEA; "> <a href="mailto:[email protected]?subject=Re%3A%20defining%20laws%20in%20isolation%20or%20%27no%20other%20force%20acting%27" style="text-decoration: none; color: #2D50FD"> Reply to group </a> </td> <td style="font-size: 12px; font-family: arial; padding: 7px 5px 5px; color: #FFF; background-color: #F2F2F2; border: 1px solid #EAEAEA; " > <a href="http://groups.yahoo.com/group/Fabric-of-Reality/post;_ylc=X3oDMTJlMDVjZHZoBF9TAzk3MzU5NzE0BGdycElkAzE4ODg2MDAEZ3Jwc3BJZAMxNzA1MDIwNTg1BHNlYwNmdHIEc2xrA250cGMEc3RpbWUDMTM4OTAxODQ2OQ--" style="text-decoration: none; color: #2D50FD">Start a New Topic</a> </td> <td style="font-size: 12px; font-family: arial; padding: 7px 5px 5px; color: #2D50FD; background-color: #F2F2F2; border: 1px solid #EAEAEA; " > <a href="http://groups.yahoo.com/group/Fabric-of-Reality/message/25606;_ylc=X3oDMTM2ajcycWY2BF9TAzk3MzU5NzE0BGdycElkAzE4ODg2MDAEZ3Jwc3BJZAMxNzA1MDIwNTg1BG1zZ0lkAzI1NjEzBHNlYwNmdHIEc2xrA3Z0cGMEc3RpbWUDMTM4OTAxODQ2OQR0cGNJZAMyNTYwNg--" style="text-decoration: none; color: #2D50FD;">Messages in this topic</a> (5) </td> </tr> </tbody> </table> <!------- Start Nav Bar ------> <!-- |**|begin egp html banner|**| --> <div id="ygrp-vital" style="background-color: #f2f2f2; font-family: Verdana; font-size: 10px; margin-bottom: 10px; padding: 10px;"> <span id="vithd" style="font-weight: bold; color: #333; text-transform: uppercase; ">Recent Activity:</span> <ul style="list-style-type: none; margin: 0; padding: 0; display: inline;"> </ul> <div style="clear: both; padding-top: 2px; color: #1e66ae;"> <a href="http://groups.yahoo.com/group/Fabric-of-Reality;_ylc=X3oDMTJlajhuYW9qBF9TAzk3MzU5NzE0BGdycElkAzE4ODg2MDAEZ3Jwc3BJZAMxNzA1MDIwNTg1BHNlYwN2dGwEc2xrA3ZnaHAEc3RpbWUDMTM4OTAxODQ2OQ--" style="text-decoration: none;">Visit Your Group</a> </div> </div> <div id="ft" style="font-family: Arial; font-size: 11px; margin-top: 5px; padding: 0 2px 0 0; clear: both;"> <a href="http://groups.yahoo.com/;_ylc=X3oDMTJkZG5lbWtyBF9TAzk3MzU5NzE0BGdycElkAzE4ODg2MDAEZ3Jwc3BJZAMxNzA1MDIwNTg1BHNlYwNmdHIEc2xrA2dmcARzdGltZQMxMzg5MDE4NDY5" style="float: left;"><img src="http://l.yimg.com/ru/static/images/yg/img/email/new_logo/logo-groups-137x15.png" height="15" width="137" alt="Yahoo! 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