Gravity Probe B: Wy Niobium? [Archive]

Replicator Creator

May13-04, 05:25 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>\nThe balls of the gyroscope of Gravity Probe B are covered by a metal\ncalled Niobium. Why? And Why Nb ?\nThanks\nBubo\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>The balls of the gyroscope of Gravity Probe B are covered by a metal
called Niobium. Why? And Why Nb ?
Thanks
Bubo

Uncle Al

May14-04, 04:10 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>Replicator Creator wrote:\n>\n> The balls of the gyroscope of Gravity Probe B are covered by a metal\n> called Niobium. Why? And Why Nb ?\n\nNiobium reproducibly goes superconducting at 9.288 K and below,\n\nMetrologia 21(4) 169-180 (1985)\n\nThe core is kept at 1.8 K during 13 months of the experiment. A\nspinning superconductor has an associated magnetic field. The\nspinning balls\' 3D position is precisely detected by SQUIDs\n(Superconducting Quantum Interference Devices) a ten-thousandth of an\ninch away. The whole experiment is contained inside multiple layers\nof normal and superconducting magnetic shields to bar external fields.\n\nA SQUID can detect a change of one quantum of magnetic flux. SQUIDs\ncan detect a change of 5x10^(-14) gauss, corresponding to a change of\nthe gyroscope\'s angular momentum vector of 0.1 milliarcseconds\ncompared to a total expected experimental accumulation of 42\nmilliarcseconds (3,600,000 milliarcseconds in one degree).\n\nBackground: An electron sitting before you dispalys an electrostatic\nfield from its electrical charge. A solid ball sitting before you\ndisplays a gravitational field from its mass. A moving electron\n(electric current) generates a magnetic field. A rotating ball\n(moving mass, a mass current) analogously creates a gravimagnetic\nfield in General Relativity. GR says that both mass and momentum\ncreate gravitation. Gravity Probe B will find out.\n\nWe expect GR (Einstein; metric gravitation theory) to perform down to\nthe last significant decimal place. Other predictive theories of\ngravitation (Weitzenboek; affine gravitation) give identical\npredictions. A test of fundametnally different metric vs. affine\ntheories of gravitation must look where they *disagree,* not where\nthey do agree.\n\nContemporary science generally lacks the cajones to fund risk - the\nrisk of failure. Contemporary science is therefore both awesomely\nproductive and woefully defective. It almost wholly lacks the ability\nto make discovery absent bootlegging or insubordination. Note that\nBednorz and Muller/IBM Zurich were threatened with termination and\nprosecution for embezzling laboratory funds vs. their stated project\nof high heat capacity cryogenic insulation. Look up their Nobel\nPrize. (IBM backed down - but it shouldn\'t have, firing the bastards\nand prosecuting them both, for admitted infractions of the rules.)\n\n--\nUncle Al\nhttp://www.mazepath.com/uncleal/qz.pdf\nhttp://www.mazepath.com/uncleal/eotvos.htm\n(Do something naughty to physics)\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>Replicator Creator wrote:
>
> The balls of the gyroscope of Gravity Probe B are covered by a metal
> called Niobium. Why? And Why Nb ?

Niobium reproducibly goes superconducting at 9.288 K and below,

Metrologia 21(4) 169-180 (1985)

The core is kept at 1.8 K during 13 months of the experiment. A
spinning superconductor has an associated magnetic field. The
spinning balls' 3D position is precisely detected by SQUIDs
(Superconducting Quantum Interference Devices) a ten-thousandth of an
inch away. The whole experiment is contained inside multiple layers
of normal and superconducting magnetic shields to bar external fields.

A SQUID can detect a change of one quantum of magnetic flux. SQUIDs
can detect a change of 5x10^(-14) gauss, corresponding to a change of
the gyroscope's angular momentum vector of .1 milliarcseconds
compared to a total expected experimental accumulation of 42
milliarcseconds (3,600,000 milliarcseconds in one degree).

Background: An electron sitting before you dispalys an electrostatic
field from its electrical charge. A solid ball sitting before you
displays a gravitational field from its mass. A moving electron
(electric current) generates a magnetic field. A rotating ball
(moving mass, a mass current) analogously creates a gravimagnetic
field in General Relativity. GR says that both mass and momentum
create gravitation. Gravity Probe B will find out.

We expect GR (Einstein; metric gravitation theory) to perform down to
the last significant decimal place. Other predictive theories of
gravitation (Weitzenboek; affine gravitation) give identical
predictions. A test of fundametnally different metric vs. affine
theories of gravitation must look where they *disagree,* not where
they do agree.

Contemporary science generally lacks the cajones to fund risk - the
risk of failure. Contemporary science is therefore both awesomely
productive and woefully defective. It almost wholly lacks the ability
to make discovery absent bootlegging or insubordination. Note that
Bednorz and Muller/IBM Zurich were threatened with termination and
prosecution for embezzling laboratory funds vs. their stated project
of high heat capacity cryogenic insulation. Look up their Nobel
Prize. (IBM backed down - but it shouldn't have, firing the bastards
and prosecuting them both, for admitted infractions of the rules.)

--
Uncle Al
http://www.mazepath.com/uncleal/qz.pdf
http://www.mazepath.com/uncleal/eotvos.htm
(Do something naughty to physics)

Douglas Natelson

May17-04, 06:17 PM

<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>Replicator Creator wrote:\n\n> The balls of the gyroscope of Gravity Probe B are covered by a metal\n> called Niobium. Why? And Why Nb ?\n\nLook here:\nhttp://einstein.stanford.edu/content/story_of_gpb/gpbsty5.html\n\nThe detection scheme for detecting gyro precession is to use\nexquisitely sensitive magnetometers to detect the London\nmoment (magnetic moment of a spinning superconductor).\nNiobium is particularly attractive because it superconducts\nat 9 K, well above liquid helium temperatures, and it can\nbe prepared in smooth, uniform films.\n\n--DN\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>Replicator Creator wrote:

> The balls of the gyroscope of Gravity Probe B are covered by a metal
> called Niobium. Why? And Why Nb ?

Look here:
http://einstein.stanford.edu/content/story_of_gpb/gpbsty5.html

The detection scheme for detecting gyro precession is to use
exquisitely sensitive magnetometers to detect the London
moment (magnetic moment of a spinning superconductor).
Niobium is particularly attractive because it superconducts
at 9 K, well above liquid helium temperatures, and it can
be prepared in smooth, uniform films.

--DN

Gordon D. Pusch

May25-04, 01:30 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>Douglas Natelson <natelson@no-spam.rice.no-spam.edu> writes:\n\n> Replicator Creator wrote:\n>\n>> The balls of the gyroscope of Gravity Probe B are covered by a metal\n>> called Niobium. Why? And Why Nb ?\n>\n> Look here:\n> http://einstein.stanford.edu/content/story_of_gpb/gpbsty5.html\n>\n> The detection scheme for detecting gyro precession is to use\n> exquisitely sensitive magnetometers to detect the London\n> moment (magnetic moment of a spinning superconductor).\n> Niobium is particularly attractive because it superconducts\n> at 9 K, well above liquid helium temperatures, and it can\n> be prepared in smooth, uniform films.\n\nIt\'s also important to note that, like many pure metals, Niobium is a\n"Type-I" superconductor, not a "Type-II" superconductor, which means that\nwhen it goes superconducting, it will automatically expel all magnetic flux\nfrom its interior via the Meissner effect (modulo the London effect), and\nthere will be no trapped "flux vortices" as would usually occur when a\n"Type-II" material goes superconducting. The fact that a "Type-I"\nsuperconductor automatically expels flux from its interior is important,\nbecause trapped flux would leave the sphere a spurious "non-London" magnetic\nmoment, which would ruin the experiment.\n\n\n-- Gordon D. Pusch\n\nperl -e \'\\$_ = "gdpusch\\@NO.xnet.SPAM.com\\n"; s/NO\\.//; s/SPAM\\.//; print;\'\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>Douglas Natelson <natelson@no-spam.rice.no-spam.edu> writes:

> Replicator Creator wrote:
>
>> The balls of the gyroscope of Gravity Probe B are covered by a metal
>> called Niobium. Why? And Why Nb ?
>
> Look here:
> http://einstein.stanford.edu/content/story_of_gpb/gpbsty5.html
>
> The detection scheme for detecting gyro precession is to use
> exquisitely sensitive magnetometers to detect the London
> moment (magnetic moment of a spinning superconductor).
> Niobium is particularly attractive because it superconducts
> at 9 K, well above liquid helium temperatures, and it can
> be prepared in smooth, uniform films.

It's also important to note that, like many pure metals, Niobium is a
"Type-I" superconductor, not a "Type-II" superconductor, which means that
when it goes superconducting, it will automatically expel all magnetic flux
from its interior via the Meissner effect (modulo the London effect), and
there will be no trapped "flux vortices" as would usually occur when a
"Type-II" material goes superconducting. The fact that a "Type-I"
superconductor automatically expels flux from its interior is important,
because trapped flux would leave the sphere a spurious "non-London" magnetic
moment, which would ruin the experiment.

-- Gordon D. Pusch

perl -e '$_ = "gdpusch\@NO.xnet.SPAM.com\n"; s/NO\.//; s/SPAM\.//; print;'