View Full Version : Mach's Principle, intertia, and radiation reaction
Blake Winter
Oct25-04, 08:09 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n\nI\'ve been reading about various explanations for Mach\'s principle and\ninertia, and a lot of them referred to the radiation reaction problem.\nI read that this problem entails some difficulty with conservation\nlaws unless treated very carefully, and so on. I also read that\nMach\'s principle is usually thought to only work along spacelike\nhypersurfaces or else to be due to some time-symmetric\n"Wheeler-Feynman" effect.\nHowever, I was thinking, if I remember correctly Thirring and Lense\nshowed that rotational inertia could result from a spinning shell of\nmatter around the object (e.g. the distant stars, approximated as a\nspinning shell). If this is so, then could we not describe an object\nwhich is initially not rotating, then starts to rotate, then stops\nagain also by describing the "outer shell" suddenly starting to spin\nat some previous time, and stopping again, in such a way as to have\nthe spinning perceived by the object at the same time as we claim he\nstarts spinning, and stopping in the same manner? This would not\ninvolve the interaction going over the spacelike hypersurface but\nrather be a result of a "previous" acceleration of the matter shell,\nfollowed by a "previous" stopping of it. Likewise, couldn\'t we\ndescribe linear acceleration as being equivalent to having a large\nmatter field all about suddenly start accelerating and then stop again\n(but of course, the field would have to start sometime in the past, so\nthat its effects reached the object at the same time as we claim it\nstarted accelerating)?\nAnd couldn\'t a similar effect be responsible for the electromagnetic\nradiation reaction problem? Of course, it would react a lot less,\nbecause there are two types of EM charge which mostly cancel, but\nwould still leave some small net field due to nonuniformity in the\ndistribution of positive and negative charge.\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>I've been reading about various explanations for Mach's principle and
inertia, and a lot of them referred to the radiation reaction problem.
I read that this problem entails some difficulty with conservation
laws unless treated very carefully, and so on. I also read that
Mach's principle is usually thought to only work along spacelike
hypersurfaces or else to be due to some time-symmetric
"Wheeler-Feynman" effect.
However, I was thinking, if I remember correctly Thirring and Lense
showed that rotational inertia could result from a spinning shell of
matter around the object (e.g. the distant stars, approximated as a
spinning shell). If this is so, then could we not describe an object
which is initially not rotating, then starts to rotate, then stops
again also by describing the "outer shell" suddenly starting to spin
at some previous time, and stopping again, in such a way as to have
the spinning perceived by the object at the same time as we claim he
starts spinning, and stopping in the same manner? This would not
involve the interaction going over the spacelike hypersurface but
rather be a result of a "previous" acceleration of the matter shell,
followed by a "previous" stopping of it. Likewise, couldn't we
describe linear acceleration as being equivalent to having a large
matter field all about suddenly start accelerating and then stop again
(but of course, the field would have to start sometime in the past, so
that its effects reached the object at the same time as we claim it
started accelerating)?
And couldn't a similar effect be responsible for the electromagnetic
radiation reaction problem? Of course, it would react a lot less,
because there are two types of EM charge which mostly cancel, but
would still leave some small net field due to nonuniformity in the
distribution of positive and negative charge.
Phillip Helbig---remove CLOTHES to reply
Oct27-04, 10:55 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nIn article <87423d2a.0410241828.24ca36f@posting.google.com>,\ nblake.winter@houghton.edu (Blake Winter) writes:\n\n> I\'ve been reading about various explanations for Mach\'s principle and\n> inertia,\n\nI have nothing to say about your post, but am following it up since\nfolks interested in it will probably be interested in my question:\n\nIs anyone doing "active research" on Mach\'s Principle?\n\nI believe there was a conference on Mach\'s Principle in Germany a few\nyears ago, but I believe that that is the only time I\'ve heard of it\noutside of accounts of a historical nature. Most sum things up by\nsaying "it could never be agreed what Mach\'s Principle actually means,\nso research on it died down".\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>In article <87423d2a.0410241828.24ca36f@posting.google.com>,
blake.winter@houghton.edu (Blake Winter) writes:
> I've been reading about various explanations for Mach's principle and
> inertia,
I have nothing to say about your post, but am following it up since
folks interested in it will probably be interested in my question:
Is anyone doing "active research" on Mach's Principle?
I believe there was a conference on Mach's Principle in Germany a few
years ago, but I believe that that is the only time I've heard of it
outside of accounts of a historical nature. Most sum things up by
saying "it could never be agreed what Mach's Principle actually means,
so research on it died down".
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>"Blake Winter" <blake.winter@houghton.edu> wrote in message\nnews:87423d2a.0410241828.24ca36f@posting. google.com...\n>\n>\n>\n> I\'ve been reading about various explanations for Mach\'s principle and\n> inertia, and a lot of them referred to the radiation reaction problem.\n> I read that this problem entails some difficulty with conservation\n> laws unless treated very carefully, and so on. I also read that\n> Mach\'s principle is usually thought to only work along spacelike\n> hypersurfaces or else to be due to some time-symmetric\n> "Wheeler-Feynman" effect.\n> However, I was thinking, if I remember correctly Thirring and Lense\n> showed that rotational inertia could result from a spinning shell of\n> matter around the object (e.g. the distant stars, approximated as a\n> spinning shell).\n\nI am quite new to the subject of frame dragging but I think you remember\nwrong. That would be Mach, contradicting one of the basic hypotheses of\nNewton, and I think it has never been demonstrated and even abandoned by\nEinstein. Thirring and Lense is said to be a prediction of a small deviation\nof the laws of Newton due to the effect of a rotating mass on matter around\nit, right?\n\nI look forward to hear a precision by someone who knows more about this!\n\nHarald\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Blake Winter" <blake.winter@houghton.edu> wrote in message
news:87423d2a.0410241828.24ca36f@posting.google.co m...
>
>
>
> I've been reading about various explanations for Mach's principle and
> inertia, and a lot of them referred to the radiation reaction problem.
> I read that this problem entails some difficulty with conservation
> laws unless treated very carefully, and so on. I also read that
> Mach's principle is usually thought to only work along spacelike
> hypersurfaces or else to be due to some time-symmetric
> "Wheeler-Feynman" effect.
> However, I was thinking, if I remember correctly Thirring and Lense
> showed that rotational inertia could result from a spinning shell of
> matter around the object (e.g. the distant stars, approximated as a
> spinning shell).
I am quite new to the subject of frame dragging but I think you remember
wrong. That would be Mach, contradicting one of the basic hypotheses of
Newton, and I think it has never been demonstrated and even abandoned by
Einstein. Thirring and Lense is said to be a prediction of a small deviation
of the laws of Newton due to the effect of a rotating mass on matter around
it, right?
I look forward to hear a precision by someone who knows more about this!
Harald
tessel@tum.bot
Nov9-04, 03:45 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>On Mon, 25 Oct 2004, Blake Winter asked about Mach\'s principle.\n\nI and others have posted here -very- extensively about this topic on many\nprevious occassions, so I\'ll be brief!\n\n> I\'ve been reading about various explanations for Mach\'s principle\n\nThe first thing to understand is that "Mach\'s principle" means many things\nto many different people, so you should never use this term without "scare\nquotes" or else a careful explanation of exactly what you have in mind.\nFor example, you can look for preprints on the ArXiv (start with the\nexposition by Bondi for a discussion of various versions of "Mach\'s\nPrinciple") and you can look for previous posts in this group.\n\n> I read that this problem entails some difficulty with conservation laws\n> unless treated very carefully, and so on. I also read that Mach\'s\n> principle is usually thought to only work along spacelike hypersurfaces\n> or else to be due to some time-symmetric "Wheeler-Feynman" effect.\n\nWhere exactly did you read all this? (If I knew, and could find the\ndocuments in question, I might be able to tell what these authors mean by\n"Mach\'s principle". Mostly likely, they mean different things, which\nwould certainly confuse a beginner! To be sure, I myself probably won\'t\nhave time to read anything you cite in reply--- but other knowledgeable\nposters here might.)\n\n> could we not describe an object which is initially not rotating, then\n> starts to rotate, then stops again also by describing the "outer shell"\n> suddenly starting to spin at some previous time, and stopping again, in\n> such a way as to have the spinning perceived by the object at the same\n> time as we claim he starts spinning, and stopping in the same manner?\n\nI didn\'t understand your real question here, but it appears you overlooked\nat least three observations which you must always keep in mind when\nconstructing thought experiments in gtr:\n\n* mass and angular momentum are conserved in gtr (although this can be\ntricky to formulate even in weak-field gtr),\n\n* according to gtr, any form of mass-energy will gravitate,\n\n* gtr is more realistic than say Newtonian gravitation, and thus much more\nrestrictive in what it considers "legal" initial conditions.\n\nIn this case, with sufficient care you can push the mystery of the\nultimate source of the angular momentum you wish to impart to your\nintially nonspinning shell off to spatial infinity, but you do need to\naccount for it. For example, in principle, you can try to model some\nobject which comes in from spatial infinity, strikes your shell and starts\nit rotating. As you can see, it is difficult to set up a thought\nexperiment with sufficient symmetry to make the analysis tractable!\n\nCompare say Maxwell\'s theory of EM, where you can postulate a charged disk\nwhich is spun by some -unmodeled- mechanical device, such as a steam\nengine, which is very helpful. But in a (classical relativistic)\ngravitation theory, such as gtr, we cannot -legally- postulate such a\ndeux-ex-machina!\n\nYou might look for past posts to this newsgroup giving explicit\ncalculations in weak-field gtr for spinning shells, spherical and\notherwise (i.e. going beyond Lense-Thirring\'s computation). Some of these\nmight be archived on John Baez\'s website "Relativity on the World Wide\nWeb", which IIRC also offers some useful pointers to further web resources\nregarding "Mach\'s principle". Also google for past posts on\ngravitomagnetism, Bel decomposition of the Riemann tensor wrt some\nobserver (analog of decomposing F_(ab) into electric and magnetic vectors\ntaken wrt some observer), radiation reaction, Vaidya thought experiments,\netc.\n\nPhilip Helbig asked:\n\n> Is anyone doing "active research" on Mach\'s Principle?\n>\n> I believe there was a conference on Mach\'s Principle in Germany a few\n> years ago,\n\nYes (I\'ve also misplaced the web citation, arghgh), and various authors\n(e.g. Ciufolini, Jantzen) continue to publish on topics which I claim are\nclosely allied to "Mach\'s Principle", e.g chestnuts like rotating disks,\nthe very difficult question of what it means to say that an object is\n"rotating" (anyone who thinks this is easy simply hasn\'t thought about it\nhard enough!), etc. I\'ve noticed that some stuff from European schools\ndoesn\'t seem to make it to the ArXiv, so be sure to searching the web. I\nthink all this work is entirely unsatisfactory, BTW, but I mostly applaud\nthe effort...\n\n> but I believe that that is the only time I\'ve heard of it outside of\n> accounts of a historical\n\nor philosphical (as in philosophy of physics/mathematics)\n\n> nature. Most sum things up by saying "it could never be agreed what\n> Mach\'s Principle actually means, so research on it died down".\n\nI think it would be fairer to say that noone has gotten very far\n(perennial claims in the literature notwithstanding). See e.g.\n\nauthor = {Ignazio Ciufolini and John Archibald Wheeler},\ntitle = {Gravitation and Inertia},\npublisher = {Princeton University Press},\nyear = 1995}\n\nwhere I think the problem in the first chapter will be evident (but the\nbook is still interesting and even inspiring). I think many folks out\nthere are privately musing (some years ago I was one of them!), since the\ninterest/importance of these questions are widely recognized, but\ncomparatively few rush into print.\n\n"T. Essel" (hiding somewhere in cyberspace)\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>On Mon, 25 Oct 2004, Blake Winter asked about Mach's principle.
I and others have posted here -very- extensively about this topic on many
previous occassions, so I'll be brief!
> I've been reading about various explanations for Mach's principle
The first thing to understand is that "Mach's principle" means many things
to many different people, so you should never use this term without "scare
quotes" or else a careful explanation of exactly what you have in mind.
For example, you can look for preprints on the ArXiv (start with the
exposition by Bondi for a discussion of various versions of "Mach's
Principle") and you can look for previous posts in this group.
> I read that this problem entails some difficulty with conservation laws
> unless treated very carefully, and so on. I also read that Mach's
> principle is usually thought to only work along spacelike hypersurfaces
> or else to be due to some time-symmetric "Wheeler-Feynman" effect.
Where exactly did you read all this? (If I knew, and could find the
documents in question, I might be able to tell what these authors mean by
"Mach's principle". Mostly likely, they mean different things, which
would certainly confuse a beginner! To be sure, I myself probably won't
have time to read anything you cite in reply--- but other knowledgeable
posters here might.)
> could we not describe an object which is initially not rotating, then
> starts to rotate, then stops again also by describing the "outer shell"
> suddenly starting to spin at some previous time, and stopping again, in
> such a way as to have the spinning perceived by the object at the same
> time as we claim he starts spinning, and stopping in the same manner?
I didn't understand your real question here, but it appears you overlooked
at least three observations which you must always keep in mind when
constructing thought experiments in gtr:
* mass and angular momentum are conserved in gtr (although this can be
tricky to formulate even in weak-field gtr),
* according to gtr, any form of mass-energy will gravitate,
* gtr is more realistic than say Newtonian gravitation, and thus much more
restrictive in what it considers "legal" initial conditions.
In this case, with sufficient care you can push the mystery of the
ultimate source of the angular momentum you wish to impart to your
intially nonspinning shell off to spatial infinity, but you do need to
account for it. For example, in principle, you can try to model some
object which comes in from spatial infinity, strikes your shell and starts
it rotating. As you can see, it is difficult to set up a thought
experiment with sufficient symmetry to make the analysis tractable!
Compare say Maxwell's theory of EM, where you can postulate a charged disk
which is spun by some -unmodeled- mechanical device, such as a steam
engine, which is very helpful. But in a (classical relativistic)
gravitation theory, such as gtr, we cannot -legally- postulate such a
deux-ex-machina!
You might look for past posts to this newsgroup giving explicit
calculations in weak-field gtr for spinning shells, spherical and
otherwise (i.e. going beyond Lense-Thirring's computation). Some of these
might be archived on John Baez's website "Relativity on the World Wide
Web", which IIRC also offers some useful pointers to further web resources
regarding "Mach's principle". Also google for past posts on
gravitomagnetism, Bel decomposition of the Riemann tensor wrt some
observer (analog of decomposing F_(ab) into electric and magnetic vectors
taken wrt some observer), radiation reaction, Vaidya thought experiments,
etc.
Philip Helbig asked:
> Is anyone doing "active research" on Mach's Principle?
>
> I believe there was a conference on Mach's Principle in Germany a few
> years ago,
Yes (I've also misplaced the web citation, arghgh), and various authors
(e.g. Ciufolini, Jantzen) continue to publish on topics which I claim are
closely allied to "Mach's Principle", e.g chestnuts like rotating disks,
the very difficult question of what it means to say that an object is
"rotating" (anyone who thinks this is easy simply hasn't thought about it
hard enough!), etc. I've noticed that some stuff from European schools
doesn't seem to make it to the ArXiv, so be sure to searching the web. I
think all this work is entirely unsatisfactory, BTW, but I mostly applaud
the effort...
> but I believe that that is the only time I've heard of it outside of
> accounts of a historical
or philosphical (as in philosophy of physics/mathematics)
> nature. Most sum things up by saying "it could never be agreed what
> Mach's Principle actually means, so research on it died down".
I think it would be fairer to say that noone has gotten very far
(perennial claims in the literature notwithstanding). See e.g.
author = {Ignazio Ciufolini and John Archibald Wheeler},
title = {Gravitation and Inertia},
publisher = {Princeton University Press},
year = 1995}
where I think the problem in the first chapter will be evident (but the
book is still interesting and even inspiring). I think many folks out
there are privately musing (some years ago I was one of them!), since the
interest/importance of these questions are widely recognized, but
comparatively few rush into print.
"T. Essel" (hiding somewhere in cyberspace)
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Philip Helbig (perhaps) asked:\n\n> Is anyone doing "active research"\n> on Mach\'s Principle?\n\nTry this paper, among many more\nhttp://www.ensmp.fr/aflb/AFLB-283/aflb283p549.pdf\n\nThere are also books, like:\n- Mach\'s Principle and the Origin of Inertia\nby M. Sachs (Editor), A.R. Roy (Editor)\n- Mach\'s Principle: From Newton\'s Bucket to Quantum Gravity,\nby Julian B. Barbour (Editor)\n- Origin of Inertia: Extended Mach\'s Principle and\nCosmological Consequences,\nby Amitabha Ghosh\n\nRegards,\ns.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Philip Helbig (perhaps) asked:
> Is anyone doing "active research"
> on Mach's Principle?
Try this paper, among many more
http://www.ensmp.fr/aflb/AFLB-283/aflb283p549.pdf
There are also books, like:
- Mach's Principle and the Origin of Inertia
by M. Sachs (Editor), A.R. Roy (Editor)
- Mach's Principle: From Newton's Bucket to Quantum Gravity,
by Julian B. Barbour (Editor)
- Origin of Inertia: Extended Mach's Principle and
Cosmological Consequences,
by Amitabha Ghosh
Regards,
s.
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