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alistair
May12-04, 01:40 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>Does the expansion of the universe have a rate of change of ACCELERATION?\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">&nbsp;&nbsp;View this Usenet post in original ASCII form </a></div><P></jabberwocky>Does the expansion of the universe have a rate of change of ACCELERATION?
Uncle Al
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>\n\nalistair wrote:\n&gt;\n&gt; Does the expansion of the universe have a rate of change of ACCELERATION?\n\nhttp://arXiv.org/abs/astro-ph/0310723\nWMAP + Sloane Digital Sky Survey\n\nAcceleration (re dark energy) appears to be increasing with time, and\nthe rate of increase is increasing with time. Several lay articles\nhave been written about this re the end of the universe\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</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">&nbsp;&nbsp;View this Usenet post in original ASCII form </a></div><P></jabberwocky>alistair wrote:
>
> Does the expansion of the universe have a rate of change of ACCELERATION?

http://arXiv.org/abs/http://www.arxiv.org/abs/astro-ph/0310723
WMAP + Sloane Digital Sky Survey

Acceleration (re dark energy) appears to be increasing with time, and
the rate of increase is increasing with time. Several lay articles
have been written about this re the end of the universe

--
Uncle Al
http://www.mazepath.com/uncleal/qz.pdf
http://www.mazepath.com/uncleal/eotvos.htm
(Do something naughty to physics)
tessel@tum.bot
May14-04, 04:09 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>Alistair asked:\n\n&gt; Does the expansion of the universe\n\nAccording to an FRW (Friedmann-Robertson-Walker) cosmological model? With\nnonzero Lambda?\n\n&gt; have a rate of change of ACCELERATION?\n\nDo you mean the standard "acceleration parameter" discussed in standard\ntextbooks in the context of FRW models?\n\nIf so, see first the undergraduate textbook\n\nauthor = {Ray D\'Inverno},\ntitle = {Introducing {E}instein\'s Relativity},\npublisher = {Clarendon Press},\nyear = 1995}\n\nwhich offers a good, easy to read discussion of FRW models (including\nnonzero Lambda). Then you can look for past posts to sci.physics.*\ncontrasting in detail two distinct notions of "acceleration parameter"\nfor nonzero Lambda FRW models.\n\nIncidentally, in another thread you claimed\n\n&gt; MOND basically says that if you double the distance of a star from the\n&gt; galactic centre, then you half the force of gravity, instead of\n&gt; quartering it as Newton\'s inverse square law would say. This is what a\n&gt; physical theory needs to explain.\n\nSince MOND should reduce to Newtonian gravity in an appropriate limit,\nclearly you must modify your description :-/\n\nA general request to all posters who have fallen into bad habits: please\nbe kind to the long-suffering moderators--- and readers!-- and make every\nattempt to write posts which are\n\n(i) concise\n\n(ii) clear\n\n(iii) correct.\n\nThis will save time and effort and -greatly- improve the impression you\nmake on others here.\n\n"T. Essel" (hiding somewhere in cyberspace)\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">&nbsp;&nbsp;View this Usenet post in original ASCII form </a></div><P></jabberwocky>Alistair asked:

> Does the expansion of the universe

According to an FRW (Friedmann-Robertson-Walker) cosmological model? With
nonzero \Lambda?

> have a rate of change of ACCELERATION?

Do you mean the standard "acceleration parameter" discussed in standard
textbooks in the context of FRW models?

If so, see first the undergraduate textbook

author = {Ray D'Inverno},
title = {Introducing {E}instein's Relativity},
publisher = {Clarendon Press},
year = 1995}

which offers a good, easy to read discussion of FRW models (including
nonzero \Lambda). Then you can look for past posts to sci.physics.*
contrasting in detail two distinct notions of "acceleration parameter"
for nonzero \Lambda FRW models.

Incidentally, in another thread you claimed

> MOND basically says that if you double the distance of a star from the
> galactic centre, then you half the force of gravity, instead of
> quartering it as Newton's inverse square law would say. This is what a
> physical theory needs to explain.

Since MOND should reduce to Newtonian gravity in an appropriate limit,
clearly you must modify your description :-/

A general request to all posters who have fallen into bad habits: please
be kind to the long-suffering moderators--- and readers!-- and make every
attempt to write posts which are

(i) concise

(ii) clear

(iii) correct.

This will save time and effort and -greatly- improve the impression you
make on others here.

"T. Essel" (hiding somewhere in cyberspace)
ebunn@lfa221051.richmond.edu
May14-04, 09:16 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>Xref: core-easynews sci.physics.research:56200\nX-Received-Date: Fri, 14 May 2004 07:15:34 MST (news.easynews.com)\n\n\nIn article &lt;861c1b21.0405080157.6b210cf9@posting.google.com&gt;, \nalistair &lt;alistair@goforit64.fsnet.co.uk&gt; wrote:\n\n&gt;Does the expansion of the universe have a rate of change of ACCELERATION?\n\nIt\'s not clear to me whether you really mean acceleration or rate of\nchange of acceleration. Either way, the answer, according to the most\nnatural-looking interpretation of our best available data, is yes.\nThe expansion appears to have positive acceleration today, and to have had\nnegative acceleration in the past. Here\'s a sample news article\nfrom last fall:\n\nhttp://www.newscientist.com/news/news.jsp?id=ns99994264\n\nThese are difficult observations, and it\'s still possible that either\nthe data or the interpretation is wrong. Personally, I think that\nthis is probably right though. There are several different lines of\nevidence that all point towards the same model of the Universe. Any\none of these lines of evidence could be wrong, but the consilience\nbetween them is very suggestive to me.\n\n-Ted\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">&nbsp;&nbsp;View this Usenet post in original ASCII form </a></div><P></jabberwocky>Xref: core-easynews sci.physics.research:56200
X-Received-Date: Fri, 14 May 2004 07:15:34 MST (news.easynews.com)


In article <861c1b21.0405080157.6b210cf9@posting.google.com>,
alistair <alistair@goforit64.fsnet.co.uk> wrote:

>Does the expansion of the universe have a rate of change of ACCELERATION?

It's not clear to me whether you really mean acceleration or rate of
change of acceleration. Either way, the answer, according to the most
natural-looking interpretation of our best available data, is yes.
The expansion appears to have positive acceleration today, and to have had
negative acceleration in the past. Here's a sample news article
from last fall:

http://www.newscientist.com/news/news.jsp?id=ns99994264

These are difficult observations, and it's still possible that either
the data or the interpretation is wrong. Personally, I think that
this is probably right though. There are several different lines of
evidence that all point towards the same model of the Universe. Any
one of these lines of evidence could be wrong, but the consilience
between them is very suggestive to me.

-Ted

--
[E-mail me at name@domain.edu, as opposed to name@machine.domain.edu.]
Gordon D. Pusch
May14-04, 09:27 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>alistair@goforit64.fsnet.co.uk (alistair) writes:\n\n&gt; Does the expansion of the universe have a rate of change of ACCELERATION?\n\nNo one knows. It was hard enough just to get a crude measurement of\nthe _sign_ of the deceleration parameter, let alone its magnitude !!!\nGetting an accurate measurement of the "cosmic jolt" is likely\nto be highly difficult for the foreseeable future; for more detail,\nsee &lt;http://www.arxiv.org/abs/gr-qc/0309109&gt; for a theoretical discussion,\nand &lt;http://www.arxiv.org/abs/astro-ph/0402512&gt; for an observational\ndiscussion.\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">&nbsp;&nbsp;View this Usenet post in original ASCII form </a></div><P></jabberwocky>alistair@goforit64.fsnet.co.uk (alistair) writes:

> Does the expansion of the universe have a rate of change of ACCELERATION?

No one knows. It was hard enough just to get a crude measurement of
the _sign_ of the deceleration parameter, let alone its magnitude !!!
Getting an accurate measurement of the "cosmic jolt" is likely
to be highly difficult for the foreseeable future; for more detail,
see <http://www.arxiv.org/abs/http://www.arxiv.org/abs/gr-qc/0309109> for a theoretical discussion,
and <http://www.arxiv.org/abs/http://www.arxiv.org/abs/astro-ph/0402512> for an observational
discussion.


-- Gordon D. Pusch

perl -e '$_ = "gdpusch\@NO.xnet.SPAM.com\n"; s/NO\.//; s/SPAM\.//; print;'
mathman
May17-04, 07:48 PM
Probably yes. After inflation, expansion slowed doen for a while, but now it is speeding up.