will Gravity Probe B speak to the "speed of gravity" issue?

robert bristow-johnson

<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>.... either indirectly (by supporting/refuting GR) or by direct measure of some sort?\n\njust curious.\n\nr b-j\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>.... either indirectly (by supporting/refuting GR) or by direct measure of some sort?

just curious.

[tex]r b-j[/tex]

robert bristow-johnson

<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>\nthanks to T. Bunn and J. Baez for setting me straight on the "particles of\nopposite mass" question. i just didn\'t account for all of the minus signs\n(namely the one on the inertial mass). so now i get it. (i\'m saying this\nhere because there is no other way for me to post a "thank you" and "i get\nit now" without posting something substantive about physics.\n\nback to this:\n\nIn article 4cbb922e.0404210824.4dc1ed41@posting.google.com, robert\nbristow-johnson at rbj@surfglobal.net wrote on 04/21/2004 16:25:\n\n> ... either indirectly (by supporting/refuting GR) or by direct measure of some\n> sort?\n\ni guess more specifically, *if* the "speed of gravity" is significantly\ndifferent than the speed of E&M, will the 40 milliarcseconds/year deflection\nof GP-B\'s gyroscope become a different value than 40 milliarcseconds/year?\n\nregarding my own study of GR, i\'m still chomping on\nhttp://pancake.uchicago.edu/~carroll/notes/grtinypdf.pdf which appears to me\nto be the best free primer on GR that i can get on the web. but i\'m not\nthere, yet.\n\nr b-j\n\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>thanks to T. Bunn and J. Baez for setting me straight on the "particles of
opposite mass" question. i just didn't account for all of the minus signs
(namely the one on the inertial mass). so now i get it. (i'm saying this
here because there is no other way for me to post a "thank you" and "i get
it now" without posting something substantive about physics.

back to this:

In article 4cbb922e.0404210824.4dc1ed41@posting.google.com, robert
bristow-johnson at rbj@surfglobal.net wrote on [itex]04/21/2004 16:25:[/itex]

> ... either indirectly (by supporting/refuting GR) or by direct measure of some
> sort?

i guess more specifically, *if* the "speed of gravity" is significantly
different than the speed of E&M, will the 40 milliarcseconds/year deflection
of [itex]GP-B's[/itex] gyroscope become a different value than 40 milliarcseconds/year?

regarding my own study of GR, i'm still chomping on
http://pancake.uchicago.edu/~carroll.../grtinypdf.pdf which appears to me
to be the best free primer on GR that i can get on the web. but i'm not
there, yet.

[tex]r b-j[/tex]

CuriousGreg

On the same topic, I was wondering whether the speed of gravity could be measured by observing the change in gravitational lensing when viewing objects beyond a supernova...

As the star's mass gets converted to energy, the lensing effect it has on more distant but near-colinear stars (or other objects) should diminish. By observing how far off-line those objects are, and how fast the gravitational lensing characteristics change, could we not determine the speed at which the gravity waves were traveling?

kopeikins

Quote by CuriousGreg

On the same topic, I was wondering whether the speed of gravity could be measured by observing the change in gravitational lensing when viewing objects beyond a supernova...

As the star's mass gets converted to energy, the lensing effect it has on more distant but near-colinear stars (or other objects) should diminish. By observing how far off-line those objects are, and how fast the gravitational lensing characteristics change, could we not determine the speed at which the gravity waves were traveling?

This kind of experiment has been done in 2002 when Jupiter passed by a quasar. It has proved that the speed of gravity, at least in the near zone of the Solar system, is the same as the speed of light. Details are in http://www.nrao.edu/pr/2003/gravity/ and math in
http://www.iop.org/EJ/abstract/0264-9381/21/13/010

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