curvature or gravitons [Archive]

a b

Oct12-04, 10:49 AM

Uncle Al

Oct12-04, 01:57 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>\na b wrote:\n>\n> Hi\n>\n> This is a stupid question but has been annoying me for\n> quite a while now (obviously im not exactly an\n> expert).. I understand when it is said that gravity\n> isnt a force (obvious from Galileo\'s experiments\n> already),\n\nDepends. Metric gravitation has spacetime curvature that is\ndefinitely not a force. Affine gravitation has spacetime torsion, and\nthat looks like an EMF force cross product. Metric and affine\ngravitation are all but indistinguishable by experiment. Only three\ndisjoint non-overlaps are experimentally accessible. Note that\ngravitation *only affects mass,* including mass currents.\n\n1) Spin-polarized test masses have been examined. The greatest mass\nfraction spin polarized solid theoretically possible is undecatiplet\nMn-55. It is 0.005 mass-% spin mass. Magnets are typically a few\nparts-per-million spin-polarized mass (electron spin and spin angular\nmometum of electron orbits are two separate cases). There is nothing\nto be seen at achievable experimental sensitivies - too dilute.\n\nhttp://www.npl.washington.edu/eotwash/spin1.html\nhttp://www.npl.washington.edu/eotwash/publications/cpta.html\nhttp://www.npl.washington.edu/eotwash/publications/cpt01.pdf\nLecture Notes in Physics 562 439 (2001)\nPhys. Rev. Lett. 70(6) 701 (1993)\nhttp://arXiv.org/abs/gr-qc/0102020\nPhys. Rev. D 42(4) 977 (1990)\nMod. Phy. Lett. A 16(12) 763 (2001)\nPhys. Uspekhi 39(6) 623 (1996)\n\n2) Macroscopic physical spin also works - if it is relativistic!\nAchievable spins in ordinary matter are not nearly enough,\n\nPhys. Rev. D 66 022002 (2002)\n<http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PRVDAQ000066000002022002000001&idtype=cvips>\nPhys. Rev. D 65 042005 (2002)\n<http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PRVDAQ000065000004042005000001&idtype=cvips>\n\nGravity Probe-B has four gyros spinning at 10,000 rpm, two parallel\nand two antiparallel, but their 70 kg housing is only spinning at\n0.778 rpm. Orbit is free fall. It is also a supremely sensitive\nphysical spin EP test. I\'ve got an inquiry into Francis Everitt at\nStanford. He\'s mulling it over (ignoring it).\n\n3) Geometric parity. Metric gravitation is parity-even\n(Equivalence Principle); affine gravitation can be parity-odd (no\nEquivalence Principle). The hemiparity Eotvos experiment of optically\nright-handed quartz against amorphous fused silica, both being\ncompositionally identical pure SiO2, is running in Huazhong\nUniversity. It will be followed by the full parity Eotvos experiment,\nleft- vs. right-handed quartz, then the hemiparity Eotvos experiment\nleft-handed quartz against fused silica. The Chinese use cylindrical\ntest masses. An American research group volunteered solid spheres but\nhas not begun an investigation.\n\nhttp://www.mazepath.com/uncleal/qz.pdf\n\nBottom line: Whether gravitation corresponds to a force or not\ndepends on your model. There is no limiting empirical evidence either\nway.\n\n> but then some books say "tidal" forces cant\n> ge "gauged away". So.. i just wanted clarification on\n> this, is it regarded as a force similar to\n> electromagnetism and weak/strong forces or is it JUST\n> manifestation of curvature ? because these seem very\n> dissimilar to me\n\nA spherical gravitation source (the Earth) has a divergent\ngravitational field. This adds quadrupole components (tidal forces)\nto a particle in free fall (a free fall solid spherical ball of water\nbecomes an ellipsoid with its long axis pointed toward the center of\nmass). In principle, considering a sufficiently small volume of space\nwill in kind reduce tidal forces to arbitrarily small magnitudes. All\nmass in the universe afftects your test mass. A perfectly flat\nMinkowski space (no curvature) therefore cannot be achieved.\n\nEotvos balance rotors have evolved to null moments of inertia at least\nthrough second order in modest volumes of space (~6 cm aross),\n\nhttp://www.npl.washington.edu/eotwash/pendc.html\nGood to 5 in 10^13 difference/average for Equivalence Principle\nhttp://www.npl.washington.edu/eotwash/m6_2.html\nGood to 1 in 10^13 difference/average for Equivalence Principle\n\nDense masses may be arrayed about the balance to further flatten the\nlocal field, or it may be buried in a bedrock chamber.\n\n> Another related question: when it is said that no one\n> really doubts the existence of graviton,\n\nQuite the contrary. There is zero evidence for its existence. The\nmath is curve fitting.\n\n> does it also\n> mean that people think gravity can be treated in the\n> same way as other forces ? For example the fact that\n> gravity affects light as well as "massive" particles\n\nIt is more complicated than that,\n\nhttp://arXiv.org/abs/gr-qc/9909014\nPhys. Rev. Lett. 92 (2004) 121101\nfalling light\n\n> does it mean spacetime really is curved or can gravity\n> be described simply as an exchange of graviton and\n> forget about "curvature of spacetime" ?\n\nNo gravitons unless you have empirical evidence. Gravitation is\ngeometry unless otherwise demonstrated.\n\n> Does graviton\n> somehow interact with photon and ? and isnt graviton\n> supposed to be the quantum of gravitational wave ? but\n> isnt there more to gravity than just gravitational\n> waves...\n\nGravitational waves are propagating quadrupolar disturbances.\nGravitation and gravitational waves are wholly different.\n\n> Its just very annoying when trying to understand the\n> difference between quantum (gauge) field theory and\n> gravity that it seems there are2 totally different\n> things. Gravitons on the other and and curvature of\n> spacetime on the other. And these are conceptually\n> totally different things.\n\nI am unaware of any theory of quantized gravitation that contains\nobservables. M-theory and lattice quantum gravitation are particulary\negregious here. If it isn\'t falsifiable by observation it isn\'t\nscience - it is mathematics or (shudder) philosophy.\n\n> And the fact that covariant derivative or connection\n> is crucial to both. Is there any easy way to explain\n> the difference of the use connection in general\n> relativity and in gauge theories of em, weak and\n> strong forces ?\n\nIs the Equivalence Principle a valid postulate? If you can identify\ntwo local test masses that fall differently in vacuum, a tremendous\nvolume of parity-even gravitation theory is simply wrong. If not,\ngravitation is not supportably modeled as a force. Start here because\nthe testing is ab initio limited, easy, inexpensive, and\nwell-characterized.\n\nGeometric parity is the last unexamined Equivalence Principle\nchallenge - and it\'s running. Quartz is a mathematically extremal\ncase for opposite parity test masses, but its atoms are light (avg.\nmw=20.028). One could go to slightly less mathematically extremal\nheavy atom cases, but those large single crystals are supremely\nexpensive to obtain (e.g., SnGa6Te10, avg. mw=106.65)\n\n--\nUncle Al\nhttp://www.mazepath.com/uncleal/\n(Toxic URL! Unsafe for children and most mammals)\nhttp://www.mazepath.com/uncleal/qz.pdf\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>a b wrote:
>
> Hi
>
> This is a stupid question but has been annoying me for
> quite a while now (obviously im not exactly an
> expert).. I understand when it is said that gravity
> isnt a force (obvious from Galileo's experiments
> already),

Depends. Metric gravitation has spacetime curvature that is
definitely not a force. Affine gravitation has spacetime torsion, and
that looks like an EMF force cross product. Metric and affine
gravitation are all but indistinguishable by experiment. Only three
disjoint non-overlaps are experimentally accessible. Note that
gravitation *only affects mass,* including mass currents.

1) Spin-polarized test masses have been examined. The greatest mass
fraction spin polarized solid theoretically possible is undecatiplet
Mn-55. It is .005 mass-% spin mass. Magnets are typically a few
parts-per-million spin-polarized mass (electron spin and spin angular
mometum of electron orbits are two separate cases). There is nothing
to be seen at achievable experimental sensitivies - too dilute.

http://www.npl.washington.edu/eotwash/spin1.html
http://www.npl.washington.edu/eotwash/publications/cpta.html
http://www.npl.washington.edu/eotwash/publications/cpt01.pdf
Lecture Notes in Physics 562 439 (2001)
Phys. Rev. Lett. 70(6) 701 (1993)
http://arXiv.org/abs/http://www.arxiv.org/abs/gr-qc/0102020
Phys. Rev. D 42(4) 977 (1990)
Mod. Phy. Lett. A 16(12) 763 (2001)
Phys. Uspekhi 39(6) 623 (1996)

2) Macroscopic physical spin also works - if it is relativistic!
Achievable spins in ordinary matter are not nearly enough,

Phys. Rev. D 66 022002 (2002)
<http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PRVDAQ000066000002022002000001&idtype=cvips>
Phys. Rev. D 65 042005 (2002)
<http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PRVDAQ000065000004042005000001&idtype=cvips>

Gravity Probe-B has four gyros spinning at 10,000 rpm, two parallel
and two antiparallel, but their 70 kg housing is only spinning at
.778 rpm. Orbit is free fall. It is also a supremely sensitive
physical spin EP test. I've got an inquiry into Francis Everitt at
Stanford. He's mulling it over (ignoring it).

3) Geometric parity. Metric gravitation is parity-even
(Equivalence Principle); affine gravitation can be parity-odd (no
Equivalence Principle). The hemiparity Eotvos experiment of optically
right-handed quartz against amorphous fused silica, both being
compositionally identical pure SiO2, is running in Huazhong
University. It will be followed by the full parity Eotvos experiment,
left- vs. right-handed quartz, then the hemiparity Eotvos experiment
left-handed quartz against fused silica. The Chinese use cylindrical
test masses. An American research group volunteered solid spheres but
has not begun an investigation.

http://www.mazepath.com/uncleal/qz.pdf

Bottom line: Whether gravitation corresponds to a force or not
depends on your model. There is no limiting empirical evidence either
way.

> but then some books say "tidal" forces cant
> ge "gauged away". So.. i just wanted clarification on
> this, is it regarded as a force similar to
> electromagnetism and weak/strong forces or is it JUST
> manifestation of curvature ? because these seem very
> dissimilar to me

A spherical gravitation source (the Earth) has a divergent
gravitational field. This adds quadrupole components (tidal forces)
to a particle in free fall (a free fall solid spherical ball of water
becomes an ellipsoid with its long axis pointed toward the center of
mass). In principle, considering a sufficiently small volume of space
will in kind reduce tidal forces to arbitrarily small magnitudes. All
mass in the universe afftects your test mass. A perfectly flat
Minkowski space (no curvature) therefore cannot be achieved.

Eotvos balance rotors have evolved to null moments of inertia at least
through second order in modest volumes of space (~6 cm aross),

http://www.npl.washington.edu/eotwash/pendc.html
Good to 5 in 10^13 difference/average for Equivalence Principle
http://www.npl.washington.edu/eotwash/m6_2.html
Good to 1 in 10^13 difference/average for Equivalence Principle

Dense masses may be arrayed about the balance to further flatten the
local field, or it may be buried in a bedrock chamber.

> Another related question: when it is said that no one
> really doubts the existence of graviton,

Quite the contrary. There is zero evidence for its existence. The
math is curve fitting.

> does it also
> mean that people think gravity can be treated in the
> same way as other forces ? For example the fact that
> gravity affects light as well as "massive" particles

It is more complicated than that,

http://arXiv.org/abs/http://www.arxiv.org/abs/gr-qc/9909014
Phys. Rev. Lett. 92 (2004) 121101
falling light

> does it mean spacetime really is curved or can gravity
> be described simply as an exchange of graviton and
> forget about "curvature of spacetime" ?

No gravitons unless you have empirical evidence. Gravitation is
geometry unless otherwise demonstrated.

> Does graviton
> somehow interact with photon and ? and isnt graviton
> supposed to be the quantum of gravitational wave ? but
> isnt there more to gravity than just gravitational
> waves...

Gravitational waves are propagating quadrupolar disturbances.
Gravitation and gravitational waves are wholly different.

> Its just very annoying when trying to understand the
> difference between quantum (gauge) field theory and
> gravity that it seems there are2 totally different
> things. Gravitons on the other and and curvature of
> spacetime on the other. And these are conceptually
> totally different things.

I am unaware of any theory of quantized gravitation that contains
observables. M-theory and lattice quantum gravitation are particulary
egregious here. If it isn't falsifiable by observation it isn't
science - it is mathematics or (shudder) philosophy.

> And the fact that covariant derivative or connection
> is crucial to both. Is there any easy way to explain
> the difference of the use connection in general
> relativity and in gauge theories of em, weak and
> strong forces ?

Is the Equivalence Principle a valid postulate? If you can identify
two local test masses that fall differently in vacuum, a tremendous
volume of parity-even gravitation theory is simply wrong. If not,
gravitation is not supportably modeled as a force. Start here because
the testing is ab initio limited, easy, inexpensive, and
well-characterized.

Geometric parity is the last unexamined Equivalence Principle
challenge - and it's running. Quartz is a mathematically extremal
case for opposite parity test masses, but its atoms are light (avg.
mw=20.028). One could go to slightly less mathematically extremal
heavy atom cases, but those large single crystals are supremely
expensive to obtain (e.g., SnGa6Te10, avg. mw=106.65)

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf