View Full Version : cold dark matter in the sun-earth solar system
<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>\nif there is a signifcant amount of cold dark matter in the galaxy and\nuniverse at large, possibly supersymmetric neutralinos,\n\nthen is there a significant amount of cold dark matter in our solar\nsystem? is there any observational evidence which would suggest that\nthe orbits of the planets require more unobserved dark matter?\n\nwhile GR\'s greatest early success over newtonian gravity is the\ncorrect prediction of the precession of the perihelion of Mercury\'s\norbit, if there is *enough* unobserved dark matter exerting a\ngravitational pull, could that also account for the the precession of\nthe perihelion of Mercury\'s orbit strictly through Newtonian gravity?\n\nhow could cold dark matter not appear to be in the solar system, but\nbe present in the universe at large?\n\nif neutrinos have mass they must exert gravity, and is there enough\ngravity resulting from neutrinos on our solarsystem which requires\n"corrections"?\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>if there is a signifcant amount of cold dark matter in the galaxy and
universe at large, possibly supersymmetric neutralinos,
then is there a significant amount of cold dark matter in our solar
system? is there any observational evidence which would suggest that
the orbits of the planets require more unobserved dark matter?
while GR's greatest early success over newtonian gravity is the
correct prediction of the precession of the perihelion of Mercury's
orbit, if there is *enough* unobserved dark matter exerting a
gravitational pull, could that also account for the the precession of
the perihelion of Mercury's orbit strictly through Newtonian gravity?
how could cold dark matter not appear to be in the solar system, but
be present in the universe at large?
if neutrinos have mass they must exert gravity, and is there enough
gravity resulting from neutrinos on our solarsystem which requires
"corrections"?
Urs Schreiber
Sep1-04, 04:52 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"Daniel" <ensabah6@yahoo.com> schrieb im Newsbeitrag\nnews:ba566c17.0408312148.6c2473a2@pos ting.google.com...\n>\n> if there is a signifcant amount of cold dark matter in the galaxy and\n> universe at large, possibly supersymmetric neutralinos,\n> then is there a significant amount of cold dark matter in our solar\n> system? is there any observational evidence which would suggest that\n> the orbits of the planets require more unobserved dark matter?\n\nThere are experiments showing evidence of WIMP drak matter right here in the\nsolar system. See this message by John Baez:\n\nhttp://groups.google.de/groups?selm=b848qo%24epr%241%40glue.ucr.edu\n\nfor some links.\n\n> if neutrinos have mass they must exert gravity, and is there enough\n> gravity resulting from neutrinos on our solarsystem which requires\n> "corrections"?\n\nThe total mass even of massive neutrinos turns out to be very small compared\nto the total amount of dark matter that is supposed to be out there.\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>"Daniel" <ensabah6@yahoo.com> schrieb im Newsbeitrag
news:ba566c17.0408312148.6c2473a2@posting.google.c om...
>
> if there is a signifcant amount of cold dark matter in the galaxy and
> universe at large, possibly supersymmetric neutralinos,
> then is there a significant amount of cold dark matter in our solar
> system? is there any observational evidence which would suggest that
> the orbits of the planets require more unobserved dark matter?
There are experiments showing evidence of WIMP drak matter right here in the
solar system. See this message by John Baez:
http://groups.google.de/groups?selm=b848qo%24epr%241%40glue.ucr.edu
for some links.
> if neutrinos have mass they must exert gravity, and is there enough
> gravity resulting from neutrinos on our solarsystem which requires
> "corrections"?
The total mass even of massive neutrinos turns out to be very small compared
to the total amount of dark matter that is supposed to be out there.
ebunn@lfa221051.richmond.edu
Sep1-04, 11:03 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>\nIn article <41358dd6\\$1@news.sentex.net>,\nUrs Schreiber <Urs.Schreiber@uni-essen.de> wrote:\n>\n>"Daniel" <ensabah6@yahoo.com> schrieb im Newsbeitrag\n>news:ba566c17.0408312148.6c2473a2@po sting.google.com...\n>>\n>> if there is a signifcant amount of cold dark matter in the galaxy and\n>> universe at large, possibly supersymmetric neutralinos,\n>> then is there a significant amount of cold dark matter in our solar\n>> system? is there any observational evidence which would suggest that\n>> the orbits of the planets require more unobserved dark matter?\n>\n>There are experiments showing evidence of WIMP dark matter right here in the\n>solar system. See this message by John Baez:\n>\n>http://groups.google.de/groups?selm=b848qo%24epr%241%40glue.ucr.edu\n>\n>f or some links.\n\nJust to be clear, this post doesn\'t refer to evidence that dark matter\nhas a detectable gravitational influence on the orbits of planets. It\ndoes refer to claimed evidence that dark matter has been found in the\nsolar system, but what\'s being described is direct (nongravitational)\ndetections of WIMP dark matter particles passing through the research\ngroup\'s lab.\n\n(As John Baez points out, these results are very controversial: one\nexperiment claims a detection, but competing groups haven\'t been able\nto replicate their results.)\n\nTo answer Daniel\'s question, the density of dark matter in our solar\nsystem isn\'t high enough to have detectable effects on planetary\norbits.\n\n(You can interpret that last statement either theoretically -- that\nis, we can estimate the local density of dark matter from theoretical\nmodels, and the effect on planetary orbits is predicted to be\nnegligible -- or experimentally -- that is, no such effects are\nactually seen. Both are true.)\n\n-Ted\n\n\n--\n[E-mail me at name@domain.edu, as opposed to name@machine.domain.edu.]\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 <41358dd6$1@news.sentex.net>,
Urs Schreiber <Urs.Schreiber@uni-essen.de> wrote:
>
>"Daniel" <ensabah6@yahoo.com> schrieb im Newsbeitrag
>news:ba566c17.0408312148.6c2473a2@posting.google.c om...
>>
>> if there is a signifcant amount of cold dark matter in the galaxy and
>> universe at large, possibly supersymmetric neutralinos,
>> then is there a significant amount of cold dark matter in our solar
>> system? is there any observational evidence which would suggest that
>> the orbits of the planets require more unobserved dark matter?
>
>There are experiments showing evidence of WIMP dark matter right here in the
>solar system. See this message by John Baez:
>
>http://groups.google.de/groups?selm=b848qo%24epr%241%40glue.ucr.edu
>
>for some links.
Just to be clear, this post doesn't refer to evidence that dark matter
has a detectable gravitational influence on the orbits of planets. It
does refer to claimed evidence that dark matter has been found in the
solar system, but what's being described is direct (nongravitational)
detections of WIMP dark matter particles passing through the research
group's lab.
(As John Baez points out, these results are very controversial: one
experiment claims a detection, but competing groups haven't been able
to replicate their results.)
To answer Daniel's question, the density of dark matter in our solar
system isn't high enough to have detectable effects on planetary
orbits.
(You can interpret that last statement either theoretically -- that
is, we can estimate the local density of dark matter from theoretical
models, and the effect on planetary orbits is predicted to be
negligible -- or experimentally -- that is, no such effects are
actually seen. Both are true.)
-Ted
--
[E-mail me at name@domain.edu, as opposed to name@machine.domain.edu.]
Arvind Rajaraman
Sep2-04, 03:26 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>ensabah6@yahoo.com (Daniel) wrote in message news:<ba566c17.0408312148.6c2473a2@posting.google. com>...\n> if there is a signifcant amount of cold dark matter in the galaxy and\n> universe at large, possibly supersymmetric neutralinos,\n>\n> then is there a significant amount of cold dark matter in our solar\n> system? is there any observational evidence which would suggest that\n> the orbits of the planets require more unobserved dark matter?\n\nThe density of dark matter in the local halo is roughly 0.3GeV/cm^3.\nThe Earth-Sun distance is roughly 1.5 X 10^{13} cm. So the amount of\ndark matter enclosed in Earth orbit is roughly 10^{40} GeV. For\ncomparison, the Sun\'s mass is about 10^{57} GeV. So the dark matter\nenclosed is 10^{-17} of the mass of the Sun. It therefore has a\nnegligible effect on the orbit.\n\nHowever, if you consider the whole galaxy, dark matter contributes\nmore than 10 times the mass of luminous matter.\n\n>\n> while GR\'s greatest early success over newtonian gravity is the\n> correct prediction of the precession of the perihelion of Mercury\'s\n> orbit, if there is *enough* unobserved dark matter exerting a\n> gravitational pull, could that also account for the the precession of\n> the perihelion of Mercury\'s orbit strictly through Newtonian gravity?\n>\n\nThe precession due to dark matter is several orders of magnitude\nsmaller than the effects from GR.\n>\n> if neutrinos have mass they must exert gravity, and is there enough\n> gravity resulting from neutrinos on our solarsystem which requires\n> "corrections"?\n\nNeutrinos form a tiny fraction of dark matter, so their effects are\neven smaller.\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>ensabah6@yahoo.com (Daniel) wrote in message news:<ba566c17.0408312148.6c2473a2@posting.google.com>...
> if there is a signifcant amount of cold dark matter in the galaxy and
> universe at large, possibly supersymmetric neutralinos,
>
> then is there a significant amount of cold dark matter in our solar
> system? is there any observational evidence which would suggest that
> the orbits of the planets require more unobserved dark matter?
The density of dark matter in the local halo is roughly .3GeV/cm^3.
The Earth-Sun distance is roughly 1.5 X 10^{13} cm. So the amount of
dark matter enclosed in Earth orbit is roughly 10^{40} GeV. For
comparison, the Sun's mass is about 10^{57} GeV. So the dark matter
enclosed is 10^{-17} of the mass of the Sun. It therefore has a
negligible effect on the orbit.
However, if you consider the whole galaxy, dark matter contributes
more than 10 times the mass of luminous matter.
>
> while GR's greatest early success over newtonian gravity is the
> correct prediction of the precession of the perihelion of Mercury's
> orbit, if there is *enough* unobserved dark matter exerting a
> gravitational pull, could that also account for the the precession of
> the perihelion of Mercury's orbit strictly through Newtonian gravity?
>
The precession due to dark matter is several orders of magnitude
smaller than the effects from GR.
>
> if neutrinos have mass they must exert gravity, and is there enough
> gravity resulting from neutrinos on our solarsystem which requires
> "corrections"?
Neutrinos form a tiny fraction of dark matter, so their effects are
even smaller.
Nicolaas Vroom
Sep2-04, 03:28 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>"Daniel" <ensabah6@yahoo.com> schreef in bericht\nnews:ba566c17.0408312148.6c2473a2@posting .google.com...\n>\n> if there is a signifcant amount of cold dark matter in the galaxy and\n> universe at large, possibly supersymmetric neutralinos,\n>\n> then is there a significant amount of cold dark matter in our solar\n> system? is there any observational evidence which would suggest that\n> the orbits of the planets require more unobserved dark matter?\n\nThe point is that you can explain the movement of the planets\nwithout the introduction of dark matter\nOn the other hand in principle it is possible that there is dark matter.\nThe whole issue depends on the physical distribution of this\ndark matter.\n\nFor example in principle the following scenario is possible:\nThe sun consists for 99% of visible matter and for 1% of\ndark matter, the last even distributed in a spherical layer around\nthe sun, all within the perihelion of Mercury.\nThat means the total mass stays the same.\nWithin this scenario the movement of the planets would be\nthe same.\nThe biggest problem with this scenario I expect would be the\nphysical behaviour of the outer layer of the Sun i.e. the behaviour\nof sun flares and sun eruptions.\n\n( I never tried a simulation were this spherical layer will be larger\nbut if it reaches until aphelion than the movement of Mercury\nwill be effected.)\n\n> while GR\'s greatest early success over newtonian gravity is the\n> correct prediction of the precession of the perihelion of Mercury\'s\n> orbit, if there is *enough* unobserved dark matter exerting a\n> gravitational pull, could that also account for the the precession of\n> the perihelion of Mercury\'s orbit strictly through Newtonian gravity?\n\nIMO this suggestion is correct.\nIn principle you could explain the behaviour of Mercury by introducing\na disc like distribution of dark matter around the equator of the Sun.\n\nThe visible almost spherical shape of the Sun does not allow\nfor such an explanation.\n\n> how could cold dark matter not appear to be in the solar system, but\n> be present in the universe at large ?\n\nThere are three issues:\n1. The amount of darkmatter in the solar system.\n2. The amount of darkmatter in galaxies\n3. The amount of darkmatter in the universe.\n\nThe answer on issue #1 is very small and almost zero.\n\nIf that answer is true than issue #2 implies that there is\nno darkmatter within the neighbourhood of any star within\nour galaxy.\nThe most probably place for dark matter is then within the\ndisc but outside the stars.\n\nWhat makes this picture difficult is the following:\nA spiral galaxy consists of two parts: a bulge and a disc\nAnd the disc also consits of two parts:\nA visible part and an invisible part.\nThis invisible part consists of small stars and can be\ncompared with the kuiper belt around the sun.\nThe difficult part is that when you introduce a small number\nof those invisible stars in a simulation, that this has a huge\neffect on the rotation curve and almost becomes flat.\n\nFor more information see the thread:\n"Galactic Rotation Curves Online?" in sci.astro.research\n\nIssue #3 is outside my competence.\n\nNicolaas Vroom\nhttp://users.pandora.be/nicvroom/\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>"Daniel" <ensabah6@yahoo.com> schreef in bericht
news:ba566c17.0408312148.6c2473a2@posting.google.c om...
>
> if there is a signifcant amount of cold dark matter in the galaxy and
> universe at large, possibly supersymmetric neutralinos,
>
> then is there a significant amount of cold dark matter in our solar
> system? is there any observational evidence which would suggest that
> the orbits of the planets require more unobserved dark matter?
The point is that you can explain the movement of the planets
without the introduction of dark matter
On the other hand in principle it is possible that there is dark matter.
The whole issue depends on the physical distribution of this
dark matter.
For example in principle the following scenario is possible:
The sun consists for 99% of visible matter and for 1% of
dark matter, the last even distributed in a spherical layer around
the sun, all within the perihelion of Mercury.
That means the total mass stays the same.
Within this scenario the movement of the planets would be
the same.
The biggest problem with this scenario I expect would be the
physical behaviour of the outer layer of the Sun i.e. the behaviour
of sun flares and sun eruptions.
( I never tried a simulation were this spherical layer will be larger
but if it reaches until aphelion than the movement of Mercury
will be effected.)
> while GR's greatest early success over newtonian gravity is the
> correct prediction of the precession of the perihelion of Mercury's
> orbit, if there is *enough* unobserved dark matter exerting a
> gravitational pull, could that also account for the the precession of
> the perihelion of Mercury's orbit strictly through Newtonian gravity?
IMO this suggestion is correct.
In principle you could explain the behaviour of Mercury by introducing
a disc like distribution of dark matter around the equator of the Sun.
The visible almost spherical shape of the Sun does not allow
for such an explanation.
> how could cold dark matter not appear to be in the solar system, but
> be present in the universe at large ?
There are three issues:
1. The amount of darkmatter in the solar system.
2. The amount of darkmatter in galaxies
3. The amount of darkmatter in the universe.
The answer on issue #1 is very small and almost zero.
If that answer is true than issue #2 implies that there is
no darkmatter within the neighbourhood of any star within
our galaxy.
The most probably place for dark matter is then within the
disc but outside the stars.
What makes this picture difficult is the following:
A spiral galaxy consists of two parts: a bulge and a disc
And the disc also consits of two parts:
A visible part and an invisible part.
This invisible part consists of small stars and can be
compared with the kuiper belt around the sun.
The difficult part is that when you introduce a small number
of those invisible stars in a simulation, that this has a huge
effect on the rotation curve and almost becomes flat.
For more information see the thread:
"Galactic Rotation Curves Online?" in sci.astro.research
Issue #3 is outside my competence.
Nicolaas Vroom
http://users.pandora.be/nicvroom/
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