View Full Version : dark energy
alistair
May17-04, 07:36 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>what is dark energy?\nIs it massless electromagnetic waves? A kind of rest mass?\nDoes it have electric charge or spin? Does it redshift as\nthe universe expands? Does it have a temperature?\nIf it is a property of space then what exactly does that mean?\nDoes anybody really have a clue as to what dark energy is?\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>what is dark energy?
Is it massless electromagnetic waves? A kind of rest mass?
Does it have electric charge or spin? Does it redshift as
the universe expands? Does it have a temperature?
If it is a property of space then what exactly does that mean?
Does anybody really have a clue as to what dark energy is?
Doug Sweetser
May29-04, 11:54 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 wrote:\n\n> what is dark energy?\n\nDark energy is an area of study that hopes to address is why does the\nUniverse appear to be increasing its rate of expansion? Gravity, as we\nunderstand it today, cannot do the trick because as an attractive\nforce, it can only slow down acceleration.\n\nIn my own personal lexicon, I call an "area of study" a topic that does\nnot have specific, concrete predictions. Einstein\'s work on gravity\nfrom 1905-1916 was an area of study. It became what I call a\n"hypothesis" when Schwarzschild found a solution, and the theory made\nthree predictions about light bending around the Sun, gravitational\nredshift (really a test of equivalence), and the precession of the\nperihelion of Mercury. A "theory" I define as a system to do many\ncalculations that have been confirmed by experiment. So with these\nmore precise than is generally used terms, general relativity went from\nand area of study, to a hypothesis, to a theory.\n\nThere are three big areas of study in gravity today: dark energy, dark\nmatter, and string theory (where the "theory" in "string theory" is a\nlabel not consistent with my above definition). Each addresses a\ndifferent issue in the study of gravity. Dark energy hopes to address\nthe acceleration of the Universe. Dark matter concerns rotation\nprofiles of disk galaxies and other large collections of matter that\nappear to be moving around in ways inconsistent with the application of\nNewton\'s law of gravity. String theory is one of several roads to\nquantum gravity.\n\nAn area of study is something where no one really has a clue what the\ntopic is about. There are labels for the main characters involved -\nvacuum energy, WIMPS, strings on the Planck scale - but any of the\nbasic properties can change with a shift in the area of study.\nResearchers in these areas struggle _in public_ to find a hypothesis,\nsomething that can be tested, so the work can transition from an area\nof study, to a testable hypothesis, to a theory. On an emotional\nlevel, there will be people who passionately support the area of study,\nas well as those who just as passionately want to ditch the entire\neffort. People investigate cold versus hot dark matter. I don\'t know\nabout the issue of temperature for dark energy, but at this point,\nanyone is free to speculate.\n\nWhen reading science news, I focus on the problem, not on the promotion\nof a particular area of study. Data came in from NASA recently adding\nmore data to the observation that the Universe is currently\naccelerating. Most of those articles promoted the dark energy area of\nstudy in the title.\n\nMy own method is to ignore most of the chatter made by people in an area\nof study. My reasoning is like this. The people working in such areas\nare some of the brightest on the planet. Think about how good people\nget at chess or piano: these folks are like that with physics. If\nthere was a solution in an area of study, one of these brilliantly\nbright people should have found it already.\n\nWe are trying to explain the behaviour of simple, dead stupid matter.\nThe math for gravity should be a wee bit simpler that EM since they are\nso darn similar classically. I don\'t think there is any dark energy,\nthere is not a gram of dark matter, and string theory will prove to be\nentirely unnecessary. Do I have any hypotheses? One concrete one is\nthat gravity waves will not have a transverse polarization. I have a\npartially worked out effort to explain the rotation profile of one\nparticular galaxy, NCG 3198. If I could find a fan of quantum field\ntheory, I think there is enough structure to my work to make a\nscattering calculation, but I don\'t have those skills today myself to\ndo it all alone. I don\'t know how different the metric I work with\nwill be in the classical tests yet because second order PPN\ncalculations get tricky technically (see a recent post of mine if\ninterested). And my health is bad. I am not confident my work will\nmake the clear move to a series of well formed hypotheses, but it is\nwhere I focus my limited means.\n\n\ndoug\nquaternions.com\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>alistair wrote:
> what is dark energy?
Dark energy is an area of study that hopes to address is why does the
Universe appear to be increasing its rate of expansion? Gravity, as we
understand it today, cannot do the trick because as an attractive
force, it can only slow down acceleration.
In my own personal lexicon, I call an "area of study" a topic that does
not have specific, concrete predictions. Einstein's work on gravity
from 1905-1916 was an area of study. It became what I call a
"hypothesis" when Schwarzschild found a solution, and the theory made
three predictions about light bending around the Sun, gravitational
redshift (really a test of equivalence), and the precession of the
perihelion of Mercury. A "theory" I define as a system to do many
calculations that have been confirmed by experiment. So with these
more precise than is generally used terms, general relativity went from
and area of study, to a hypothesis, to a theory.
There are three big areas of study in gravity today: dark energy, dark
matter, and string theory (where the "theory" in "string theory" is a
label not consistent with my above definition). Each addresses a
different issue in the study of gravity. Dark energy hopes to address
the acceleration of the Universe. Dark matter concerns rotation
profiles of disk galaxies and other large collections of matter that
appear to be moving around in ways inconsistent with the application of
Newton's law of gravity. String theory is one of several roads to
quantum gravity.
An area of study is something where no one really has a clue what the
topic is about. There are labels for the main characters involved -
vacuum energy, WIMPS, strings on the Planck scale - but any of the
basic properties can change with a shift in the area of study.
Researchers in these areas struggle _in public_ to find a hypothesis,
something that can be tested, so the work can transition from an area
of study, to a testable hypothesis, to a theory. On an emotional
level, there will be people who passionately support the area of study,
as well as those who just as passionately want to ditch the entire
effort. People investigate cold versus hot dark matter. I don't know
about the issue of temperature for dark energy, but at this point,
anyone is free to speculate.
When reading science news, I focus on the problem, not on the promotion
of a particular area of study. Data came in from NASA recently adding
more data to the observation that the Universe is currently
accelerating. Most of those articles promoted the dark energy area of
study in the title.
My own method is to ignore most of the chatter made by people in an area
of study. My reasoning is like this. The people working in such areas
are some of the brightest on the planet. Think about how good people
get at chess or piano: these folks are like that with physics. If
there was a solution in an area of study, one of these brilliantly
bright people should have found it already.
We are trying to explain the behaviour of simple, dead stupid matter.
The math for gravity should be a wee bit simpler that EM since they are
so darn similar classically. I don't think there is any dark energy,
there is not a gram of dark matter, and string theory will prove to be
entirely unnecessary. Do I have any hypotheses? One concrete one is
that gravity waves will not have a transverse polarization. I have a
partially worked out effort to explain the rotation profile of one
particular galaxy, NCG 3198. If I could find a fan of quantum field
theory, I think there is enough structure to my work to make a
scattering calculation, but I don't have those skills today myself to
do it all alone. I don't know how different the metric I work with
will be in the classical tests yet because second order PPN
calculations get tricky technically (see a recent post of mine if
interested). And my health is bad. I am not confident my work will
make the clear move to a series of well formed hypotheses, but it is
where I focus my limited means.
doug
quaternions.com
Phillip Helbig---remove CLOTHES to reply
May31-04, 06:26 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 <c920ul\\$s9q\\$1@pcls4.std.com>, Doug Sweetser\n<sweetser@alum.mit.edu> writes:\n\n> alistair wrote:\n>\n> > what is dark energy?\n>\n> Dark energy is an area of study that hopes to address is why does the\n> Universe appear to be increasing its rate of expansion? Gravity, as we\n> understand it today, cannot do the trick because as an attractive\n> force, it can only slow down acceleration.\n>\n> In my own personal lexicon, I call an "area of study" a topic that does\n> not have specific, concrete predictions.\n\nALL the observational data are consistent with "dark energy" being the\ntraditional cosmological constant. This makes very concrete\npredictions: what the apparent magnitude of standard candles will be at\nredshifts where they have not yet been observed, what the age of the\nuniverse is etc.\n\n> My own method is to ignore most of the chatter made by people in an area\n> of study. My reasoning is like this. The people working in such areas\n> are some of the brightest on the planet. Think about how good people\n> get at chess or piano: these folks are like that with physics. If\n> there was a solution in an area of study, one of these brilliantly\n> bright people should have found it already.\n\nAs (if I recall correctly) Gell-Mann said about Hawking, if you know the\nwave function of the universe, why aren\'t you rich?\n\nSince the acceleration has been forced on even non-believers by the\nobservations, there have been LOTS of theories as to the "cause" of it.\nPresumably, almost all of these are wrong.\n\nI think one needs to separate the rather strong observational data from\nthe large number of theoretical papers about possible "causes" of dark\nenergy. I have to admit my scepticism is increased by the fact that if\nthe cosmological constant appears so "easily and naturally", why wasn\'t\nthe paper published before the convincing observations were there?\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 <c920ul$s9q$1@pcls4.std.com>, Doug Sweetser
<sweetser@alum.mit.edu> writes:
> alistair wrote:
>
> > what is dark energy?
>
> Dark energy is an area of study that hopes to address is why does the
> Universe appear to be increasing its rate of expansion? Gravity, as we
> understand it today, cannot do the trick because as an attractive
> force, it can only slow down acceleration.
>
> In my own personal lexicon, I call an "area of study" a topic that does
> not have specific, concrete predictions.
ALL the observational data are consistent with "dark energy" being the
traditional cosmological constant. This makes very concrete
predictions: what the apparent magnitude of standard candles will be at
redshifts where they have not yet been observed, what the age of the
universe is etc.
> My own method is to ignore most of the chatter made by people in an area
> of study. My reasoning is like this. The people working in such areas
> are some of the brightest on the planet. Think about how good people
> get at chess or piano: these folks are like that with physics. If
> there was a solution in an area of study, one of these brilliantly
> bright people should have found it already.
As (if I recall correctly) Gell-Mann said about Hawking, if you know the
wave function of the universe, why aren't you rich?
Since the acceleration has been forced on even non-believers by the
observations, there have been LOTS of theories as to the "cause" of it.
Presumably, almost all of these are wrong.
I think one needs to separate the rather strong observational data from
the large number of theoretical papers about possible "causes" of dark
energy. I have to admit my scepticism is increased by the fact that if
the cosmological constant appears so "easily and naturally", why wasn't
the paper published before the convincing observations were there?
Jim Jastrzebski
May31-04, 04:20 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>"Doug Sweetser" <sweetser@alum.mit.edu> wrote in message\nnews:c920ul\\$s9q\\$1@pcls4.std.com...\n\ n> Dark energy is an area of study that hopes to address is why does the\n> Universe appear to be increasing its rate of expansion? Gravity, as we\n> understand it today, cannot do the trick because as an attractive\n> force, it can only slow down acceleration.\n\nThat\'s not completely correct. Gravity, "as we understand\nit today", only simulates a force because it looks like causing\naccelerations in ordinary (3D) space. It is surely not attractive\nnor repulsive, the same as any inertial force that gravity\nactually is. Therefore it seems that the space could either\nexpand or contract regardless of the amount of energy\naround.\n\nIntroducing forces into gravity would change it from the\nEinsteinian one back into Newtonian plus "relativistic\ncorrections" (PPN model). It wouldn\'t be physics in the\nsense that it wouldn\'t enhance our understanding of nature\nbut it would be a phenomenological theory based on\nappearances and matching some math to them. Not what\nphysics is for but what very well fits the destiny of applied\nmath.\n\n> My own method is to ignore most of the chatter made by people in an area\n> of study. My reasoning is like this. The people working in such areas\n> are some of the brightest on the planet. Think about how good people\n> get at chess or piano: these folks are like that with physics. If\n> there was a solution in an area of study, one of these brilliantly\n> bright people should have found it already.\n\nThat\'s not completely correct. The studies show that brilliant scientists\nrarely make discoveries. They are made by people like Einstein, who\ncouldn\'t even participate in discussion of math his own theory because\nthey were far over his head (apparently he said that he stopped\nunderstanding his theory when the mathematicians started explaining\nit). Yet Einstein had enough understanding of physics that in 1950 he\nproposed to drop the condition of symmetry of the spacetime metric\n(in "On the Generalized Theory of Gravitation"). Accidentally this\nproposition makes "dark energy" unnecessary to explain why we see\nthe accelerating expansion. Also why we see the expansion at all.\nAnd it also restores the validity of the principle of conservation of\nenergy that brilliant people traded for the expansion of the univerese\nthat they liked better. Unfortunately, doing all those things, Einstein\'s\nproposition also requires that the geometry of spacetime must be\nnon Riemannian, which if accepted, would put a lot of brilliant\npeople out of business. So it can\'t be done.\n\n> We are trying to explain the behaviour of simple, dead stupid matter.\n> The math for gravity should be a wee bit simpler that EM since they are\n> so darn similar classically.\n\nThat\'s not completely correct. Some extremely simple things have\nextremely complicated math. Just take 3 body problem that nature\nsolves effortlessly and instantly.\n\n> I don\'t think there is any dark energy,\n> there is not a gram of dark matter, and string theory will prove to be\n> entirely unnecessary.\n\nThat\'s completely correct. :-)\n\n> doug\n> quaternions.com\n\n-- Jim\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>"Doug Sweetser" <sweetser@alum.mit.edu> wrote in message
news:c920ul$s9q$1@pcls4.std.com...
> Dark energy is an area of study that hopes to address is why does the
> Universe appear to be increasing its rate of expansion? Gravity, as we
> understand it today, cannot do the trick because as an attractive
> force, it can only slow down acceleration.
That's not completely correct. Gravity, "as we understand
it today", only simulates a force because it looks like causing
accelerations in ordinary (3D) space. It is surely not attractive
nor repulsive, the same as any inertial force that gravity
actually is. Therefore it seems that the space could either
expand or contract regardless of the amount of energy
around.
Introducing forces into gravity would change it from the
Einsteinian one back into Newtonian plus "relativistic
corrections" (PPN model). It wouldn't be physics in the
sense that it wouldn't enhance our understanding of nature
but it would be a phenomenological theory based on
appearances and matching some math to them. Not what
physics is for but what very well fits the destiny of applied
math.
> My own method is to ignore most of the chatter made by people in an area
> of study. My reasoning is like this. The people working in such areas
> are some of the brightest on the planet. Think about how good people
> get at chess or piano: these folks are like that with physics. If
> there was a solution in an area of study, one of these brilliantly
> bright people should have found it already.
That's not completely correct. The studies show that brilliant scientists
rarely make discoveries. They are made by people like Einstein, who
couldn't even participate in discussion of math his own theory because
they were far over his head (apparently he said that he stopped
understanding his theory when the mathematicians started explaining
it). Yet Einstein had enough understanding of physics that in 1950 he
proposed to drop the condition of symmetry of the spacetime metric
(in "On the Generalized Theory of Gravitation"). Accidentally this
proposition makes "dark energy" unnecessary to explain why we see
the accelerating expansion. Also why we see the expansion at all.
And it also restores the validity of the principle of conservation of
energy that brilliant people traded for the expansion of the univerese
that they liked better. Unfortunately, doing all those things, Einstein's
proposition also requires that the geometry of spacetime must be
non Riemannian, which if accepted, would put a lot of brilliant
people out of business. So it can't be done.
> We are trying to explain the behaviour of simple, dead stupid matter.
> The math for gravity should be a wee bit simpler that EM since they are
> so darn similar classically.
That's not completely correct. Some extremely simple things have
extremely complicated math. Just take 3 body problem that nature
solves effortlessly and instantly.
> I don't think there is any dark energy,
> there is not a gram of dark matter, and string theory will prove to be
> entirely unnecessary.
That's completely correct. :-)
> doug
> quaternions.com
-- Jim
alistair
Jun1-04, 04:43 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>\nDOUG SWEETSER:\n"I don\'t think there is any dark energy"\n\nALISTAIR writes:\n\nSteven Weinberg thinks there might be. I saw somewhere on the web that\nhe said " "Dark energy is the bone in the throat for cosmologists and\nparticle physicists."\n\n\n[Moderator\'s note:\n\n1) As has been explained by experts in this thread, the\n/\\CDM standard model of cosmology, which says that dark energy makes\nup roughly 70% of the energy density of the universe, is highly favored\nby data and internal consistency and is generally taken to be correct, not\njust by Steven Weinberg.\n\n2) All participants of this discussion are highly encouraged to use the well\nestablished conventions for formatting posts, in particular concerning\nquotations. See http://www-stud.uni-essen.de/~sb0264/HowToPost.html .\n\n-usc]\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>DOUG SWEETSER:
"I don't think there is any dark energy"
ALISTAIR writes:
Steven Weinberg thinks there might be. I saw somewhere on the web that
he said " "Dark energy is the bone in the throat for cosmologists and
particle physicists."
[Moderator's note:
1) As has been explained by experts in this thread, the
/\CDM standard model of cosmology, which says that dark energy makes
up roughly 70% of the energy density of the universe, is highly favored
by data and internal consistency and is generally taken to be correct, not
just by Steven Weinberg.
2) All participants of this discussion are highly encouraged to use the well
established conventions for formatting posts, in particular concerning
quotations. See http://www-stud.uni-essen.de/~sb0264/HowToPost.html .
-usc]
Doug Sweetser
Jun1-04, 02:12 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>Hello:\n\nUrs wrote:\n\n> 1) As has been explained by experts in this thread, the\n> /\\CDM standard model of cosmology, which says that dark energy makes\n> up roughly 70% of the energy density of the universe, is highly\n> favored by data and internal consistency and is generally taken to be\n> correct, not just by Steven Weinberg.\n\nI think there is an ever improving set of data saying there is a\nproblem. The models are up for grabs. I thought CDM stood for "cold\ndark matter." Dark matter addresses a different issue than dark\nenergy. Dark energy is the cosmological constant. Yes, lots of people\ndiscuss this issue, but no one should have a lot of confidence in\neither dark matter or dark energy. They are important models to keep\nworking on, but I will call the bluff.\n\n\ndoug\nquaternions.com\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>Hello:
Urs wrote:
> 1) As has been explained by experts in this thread, the
> /\CDM standard model of cosmology, which says that dark energy makes
> up roughly 70% of the energy density of the universe, is highly
> favored by data and internal consistency and is generally taken to be
> correct, not just by Steven Weinberg.
I think there is an ever improving set of data saying there is a
problem. The models are up for grabs. I thought CDM stood for "cold
dark matter." Dark matter addresses a different issue than dark
energy. Dark energy is the cosmological constant. Yes, lots of people
discuss this issue, but no one should have a lot of confidence in
either dark matter or dark energy. They are important models to keep
working on, but I will call the bluff.
doug
quaternions.com
Urs Schreiber
Jun1-04, 02:24 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>\n"Doug Sweetser" <sweetser@alum.mit.edu> schrieb im Newsbeitrag\nnews:c9hqbo\\$kj5\\$1@pcls4.std.com.. .\n> Hello:\n>\n> Urs wrote:\n>\n> > 1) As has been explained by experts in this thread, the\n> > /\\CDM standard model of cosmology, which says that dark energy makes\n> > up roughly 70% of the energy density of the universe, is highly\n> > favored by data and internal consistency and is generally taken to be\n> > correct, not just by Steven Weinberg.\n>\n> I think there is an ever improving set of data saying there is a\n> problem. The models are up for grabs. I thought CDM stood for "cold\n> dark matter." Dark matter addresses a different issue than dark\n> energy. Dark energy is the cosmological constant. Yes, lots of people\n> discuss this issue, but no one should have a lot of confidence in\n> either dark matter or dark energy. They are important models to keep\n> working on, but I will call the bluff.\n\n"/\\CDM" (read: "Lambda CDM") is the shorthand for the cosmological model\nwhich includes a cosmological constant (capital Lambda) as well as cold dark\nmatter (in addition to the ordinary matter) which has been spectacularly\nconfirmed by recent experimental data. For more information on this issue\nthere is a very nice review by Sean Carroll\n\nhttp://pancake.uchicago.edu/~carroll/preposterous.html .\n\nEverybody trying to challenge widely accepted results is well advised to\nfirst acquaint himself with the theory in question.\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>"Doug Sweetser" <sweetser@alum.mit.edu> schrieb im Newsbeitrag
news:c9hqbo$kj5$1@pcls4.std.com...
> Hello:
>
> Urs wrote:
>
> > 1) As has been explained by experts in this thread, the
> > /\CDM standard model of cosmology, which says that dark energy makes
> > up roughly 70% of the energy density of the universe, is highly
> > favored by data and internal consistency and is generally taken to be
> > correct, not just by Steven Weinberg.
>
> I think there is an ever improving set of data saying there is a
> problem. The models are up for grabs. I thought CDM stood for "cold
> dark matter." Dark matter addresses a different issue than dark
> energy. Dark energy is the cosmological constant. Yes, lots of people
> discuss this issue, but no one should have a lot of confidence in
> either dark matter or dark energy. They are important models to keep
> working on, but I will call the bluff.
"/\CDM" (read: "\Lambda CDM") is the shorthand for the cosmological model
which includes a cosmological constant (capital \Lambda) as well as cold dark
matter (in addition to the ordinary matter) which has been spectacularly
confirmed by recent experimental data. For more information on this issue
there is a very nice review by Sean Carroll
http://pancake.uchicago.edu/~carroll/preposterous.html .
Everybody trying to challenge widely accepted results is well advised to
first acquaint himself with the theory in question.
Phillip Helbig---remove CLOTHES to reply
Jun2-04, 03:56 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\nIn article <c9hqbo\\$kj5\\$1@pcls4.std.com>, Doug Sweetser\n<sweetser@alum.mit.edu> writes:\n\n>\n> > 1) As has been explained by experts in this thread, the\n> > /\\CDM standard model of cosmology, which says that dark energy makes\n> > up roughly 70% of the energy density of the universe, is highly\n> > favored by data and internal consistency and is generally taken to be\n> > correct, not just by Steven Weinberg.\n>\n> I think there is an ever improving set of data saying there is a\n> problem.\n\nCan you point us to some refereed-journal articles discussing these\ndata?\n\n> The models are up for grabs. I thought CDM stood for "cold\n> dark matter."\n\nIt does.\n\n> Dark matter addresses a different issue than dark\n> energy.\n\nIndeed.\n\n> Dark energy is the cosmological constant.\n\nYes.\n\nWhere\'s the problem?\n\nHistorically, there has ALWAYS been evidence for dark matter, at least\nsince Zwicky\'s work on galaxy clusters in the 1930s. Evidence for the\ncosmological constant is much more recent. In the past, most people\nignored it until the data forced it upon them. Another approach,\nfollowed by a minority, was to say "hey, we don\'t know that much about\nthe universe yes; let\'s just keep this as a free parameter and see what\nthe data say". The two concepts, dark matter and the cosmological\nconstant, really have little to do with one another.\n\nSomething of a red herring appeared in the late 1980s and early 1990s,\nwhen inflation\'s prediction of a flat universe, coupled with the lack of\nother need for a cosmological constant at the time, led some people to\nadd the remaining amount of matter to allow Omega to be 1 to the well\nestablished dark matter needed on the scales of galaxies and clusters of\ngalaxies. However, at the time there was certainly no convincing\nevidence of inflation (even today, it\'s not conclusive), an NO\nobservational evidence for this extra dark matter.\n\nNow, it might seem to some that this extra dark matter has been\n"replaced" by the cosmological constant in the current standard model.\nTo some extent, this is true, but there are several important\ndifferences. First, there is now very convincing OBSERVATIONAL evidence\nthat the universe is flat (from the CMB). Since the strongest signal in\nthe CMB, the position of the first acoustic peak, essentially measures\nthe sum of Omega_matter and the cosmological constant, this is a rather\nmodel-independent measurement. Subtract the measured value of Omega\n(from a variety of tests which assume neither flatness nor a value for\nthe cosmological constant) from 1 and you get a value for the\ncosmological constant. Thus, just the CMB and measurements of Omega\nlead one to the cosmological constant. One can then do a completely\ndifferent set of observations at completely different redshifts, namely\nlooking at the apparent magnitude of standard candles (supernovae---and\nA LOT of work has been put in to showing that they are standard\ncandles), and one finds that a cosmological constant is required to\nexplain the observations. These observations measure roughly Omega -\nlambda, whereas the CMB measures essentially Omega + lambda. Two\nequations, two unknowns, solve for both. The solution has Omega equal\nto that which is observed by more direct, local methods. So there is a\nconsistency check. In addition, as far as I know there are NO\nobservations in conflict with this standard model, and, although no one\ncosmological test on its own will pin down the values of the\ncosmological parameters, several independent combinations of\ncosmological tests will.\n\nIn the last 15 years, cosmology has moved from being a mainly\ntheoretical pursuit to being a data-driven science. Any alternative\nideas have to explain A LOT of observations. That wasn\'t the case 15\nyears ago, when there weren\'t that many observations to explain.\n\nOf course, there are many theoretical papers in cosmology attempting to\n"explain" the "origin of dark energy". Obviously, most of them are\nwrong, so it\'s not a stretch to entertain the possibility that all of\nthem are. I think these ideas will end up on the scrap-heap of science,\nalong with early observational efforts to determine the cosmological\nparameters by observation with woefully inadequate instruments, lack of\nunderstanding of evolutionary processes and negligence of selection\neffects. In other words, the main event and the side show have swapped\nplaces.\n\n> Yes, lots of people\n> discuss this issue, but no one should have a lot of confidence in\n> either dark matter or dark energy. They are important models to keep\n> working on, but I will call the bluff.\n\nWhat do you think is the problem? Even if one doesn\'t "believe" in dark\nenergy or dark matter, one has to come up with an explanation for the\ndata, and according to Occam\'s razor it shouldn\'t be more complicated\nthan the explanation it is trying to replace.\n\nNote that an observation and its explanation are two different things.\nPeople saw that apples fell long before Einstein, and even long before\nNewton. The fact that a theory of gravity was lacking shouldn\'t have\nled one to believe that perhaps apples don\'t fall. Similarly, lack of\nunderstanding about the cosmological constant shouldn\'t lead one to\ndoubt the observations.\n\nScience isn\'t a collection of facts, it\'s a way of thinking. Biology\nwasn\'t somehow "incomplete" before gorillas were discovered, even though\nthey didn\'t appear in pre-gorilla biology.\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>In article <c9hqbo$kj5$1@pcls4.std.com>, Doug Sweetser
<sweetser@alum.mit.edu> writes:
>
> > 1) As has been explained by experts in this thread, the
> > /\CDM standard model of cosmology, which says that dark energy makes
> > up roughly 70% of the energy density of the universe, is highly
> > favored by data and internal consistency and is generally taken to be
> > correct, not just by Steven Weinberg.
>
> I think there is an ever improving set of data saying there is a
> problem.
Can you point us to some refereed-journal articles discussing these
data?
> The models are up for grabs. I thought CDM stood for "cold
> dark matter."
It does.
> Dark matter addresses a different issue than dark
> energy.
Indeed.
> Dark energy is the cosmological constant.
Yes.
Where's the problem?
Historically, there has ALWAYS been evidence for dark matter, at least
since Zwicky's work on galaxy clusters in the 1930s. Evidence for the
cosmological constant is much more recent. In the past, most people
ignored it until the data forced it upon them. Another approach,
followed by a minority, was to say "hey, we don't know that much about
the universe yes; let's just keep this as a free parameter and see what
the data say". The two concepts, dark matter and the cosmological
constant, really have little to do with one another.
Something of a red herring appeared in the late 1980s and early 1990s,
when inflation's prediction of a flat universe, coupled with the lack of
other need for a cosmological constant at the time, led some people to
add the remaining amount of matter to allow \Omega to be 1 to the well
established dark matter needed on the scales of galaxies and clusters of
galaxies. However, at the time there was certainly no convincing
evidence of inflation (even today, it's not conclusive), an NO
observational evidence for this extra dark matter.
Now, it might seem to some that this extra dark matter has been
"replaced" by the cosmological constant in the current standard model.
To some extent, this is true, but there are several important
differences. First, there is now very convincing OBSERVATIONAL evidence
that the universe is flat (from the CMB). Since the strongest signal in
the CMB, the position of the first acoustic peak, essentially measures
the sum of \Omega_matter and the cosmological constant, this is a rather
model-independent measurement. Subtract the measured value of \Omega
(from a variety of tests which assume neither flatness nor a value for
the cosmological constant) from 1 and you get a value for the
cosmological constant. Thus, just the CMB and measurements of \Omega
lead one to the cosmological constant. One can then do a completely
different set of observations at completely different redshifts, namely
looking at the apparent magnitude of standard candles (supernovae---and
A LOT of work has been put in to showing that they are standard
candles), and one finds that a cosmological constant is required to
explain the observations. These observations measure roughly \Omega -\lambda, whereas the CMB measures essentially \Omega + \lambda. Two
equations, two unknowns, solve for both. The solution has \Omega equal
to that which is observed by more direct, local methods. So there is a
consistency check. In addition, as far as I know there are NO
observations in conflict with this standard model, and, although no one
cosmological test on its own will pin down the values of the
cosmological parameters, several independent combinations of
cosmological tests will.
In the last 15 years, cosmology has moved from being a mainly
theoretical pursuit to being a data-driven science. Any alternative
ideas have to explain A LOT of observations. That wasn't the case 15
years ago, when there weren't that many observations to explain.
Of course, there are many theoretical papers in cosmology attempting to
"explain" the "origin of dark energy". Obviously, most of them are
wrong, so it's not a stretch to entertain the possibility that all of
them are. I think these ideas will end up on the scrap-heap of science,
along with early observational efforts to determine the cosmological
parameters by observation with woefully inadequate instruments, lack of
understanding of evolutionary processes and negligence of selection
effects. In other words, the main event and the side show have swapped
places.
> Yes, lots of people
> discuss this issue, but no one should have a lot of confidence in
> either dark matter or dark energy. They are important models to keep
> working on, but I will call the bluff.
What do you think is the problem? Even if one doesn't "believe" in dark
energy or dark matter, one has to come up with an explanation for the
data, and according to Occam's razor it shouldn't be more complicated
than the explanation it is trying to replace.
Note that an observation and its explanation are two different things.
People saw that apples fell long before Einstein, and even long before
Newton. The fact that a theory of gravity was lacking shouldn't have
led one to believe that perhaps apples don't fall. Similarly, lack of
understanding about the cosmological constant shouldn't lead one to
doubt the observations.
Science isn't a collection of facts, it's a way of thinking. Biology
wasn't somehow "incomplete" before gorillas were discovered, even though
they didn't appear in pre-gorilla biology.
greywolf42
Jun2-04, 01:53 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>\nPhillip Helbig---remove CLOTHES to reply <helbig@astro.multiCLOTHESvax.de>\nwrote in message news:c9aim0\\$cu\\$3@online.de...\n>\n> In article <c920ul\\$s9q\\$1@pcls4.std.com>, Doug Sweetser\n> <sweetser@alum.mit.edu> writes:\n>\n> > alistair wrote:\n> >\n> > > what is dark energy?\n> >\n> > Dark energy is an area of study that hopes to address is why does the\n> > Universe appear to be increasing its rate of expansion? Gravity, as we\n> > understand it today, cannot do the trick because as an attractive\n> > force, it can only slow down acceleration.\n> >\n> > In my own personal lexicon, I call an "area of study" a topic that does\n> > not have specific, concrete predictions.\n>\n> ALL the observational data are consistent with "dark energy" being the\n> traditional cosmological constant.\n\nThat\'s because the data all measure the same physical observable. The\nnonlinearity of the redshift-distance relationship. It is this single\nobservable from which the "cosmological constant" is calculated.\n\n> This makes very concrete\n> predictions: what the apparent magnitude of standard candles will be at\n> redshifts where they have not yet been observed,\n\nThese aren\'t predictions. The "CC" is back calculated from these very\nitems.\n\n> what the age of the universe is etc.\n\nI\'m not aware of a calculation of the age of the universe that rests upon\nthe assumption of the cosmological constant. Could you point me to a\nreference?\n\n> > My own method is to ignore most of the chatter made by people in an area\n> > of study. My reasoning is like this. The people working in such areas\n> > are some of the brightest on the planet. Think about how good people\n> > get at chess or piano: these folks are like that with physics. If\n> > there was a solution in an area of study, one of these brilliantly\n> > bright people should have found it already.\n>\n> As (if I recall correctly) Gell-Mann said about Hawking, if you know the\n> wave function of the universe, why aren\'t you rich?\n>\n> Since the acceleration has been forced on even non-believers by the\n> observations, there have been LOTS of theories as to the "cause" of it.\n\nThe nonlinear redshift-distance observations was predicted by\n\'non-believers\'. (By the \'tired light\' crowd.)\n\n> Presumably, almost all of these are wrong.\n\nYes. And the cosmological constant theory is only one of the \'lots\' of\ntheories, for which most will be wrong.\n\n> I think one needs to separate the rather strong observational data from\n> the large number of theoretical papers about possible "causes" of dark\n> energy.\n\nYou mean from the possible \'causes\' of the nonlinear redshift-distance\nrelationship.\n\n"Dark energy" is a postulated cause of the observation. Dark energy is not\nan observation.\n\n> I have to admit my scepticism is increased by the fact that if\n> the cosmological constant appears so "easily and naturally", why wasn\'t\n> the paper published before the convincing observations were there?\n\nOn that we certainly agree.\n\n--\ngreywolf42\nubi dubium ibi libertas\n{remove planet for return e-mail}\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>Phillip Helbig---remove CLOTHES to reply <helbig@astro.multiCLOTHESvax.de>
wrote in message news:c9aim0$cu$3@online.de...
>
> In article <c920ul$s9q$1@pcls4.std.com>, Doug Sweetser
> <sweetser@alum.mit.edu> writes:
>
> > alistair wrote:
> >
> > > what is dark energy?
> >
> > Dark energy is an area of study that hopes to address is why does the
> > Universe appear to be increasing its rate of expansion? Gravity, as we
> > understand it today, cannot do the trick because as an attractive
> > force, it can only slow down acceleration.
> >
> > In my own personal lexicon, I call an "area of study" a topic that does
> > not have specific, concrete predictions.
>
> ALL the observational data are consistent with "dark energy" being the
> traditional cosmological constant.
That's because the data all measure the same physical observable. The
nonlinearity of the redshift-distance relationship. It is this single
observable from which the "cosmological constant" is calculated.
> This makes very concrete
> predictions: what the apparent magnitude of standard candles will be at
> redshifts where they have not yet been observed,
These aren't predictions. The "CC" is back calculated from these very
items.
> what the age of the universe is etc.
I'm not aware of a calculation of the age of the universe that rests upon
the assumption of the cosmological constant. Could you point me to a
reference?
> > My own method is to ignore most of the chatter made by people in an area
> > of study. My reasoning is like this. The people working in such areas
> > are some of the brightest on the planet. Think about how good people
> > get at chess or piano: these folks are like that with physics. If
> > there was a solution in an area of study, one of these brilliantly
> > bright people should have found it already.
>
> As (if I recall correctly) Gell-Mann said about Hawking, if you know the
> wave function of the universe, why aren't you rich?
>
> Since the acceleration has been forced on even non-believers by the
> observations, there have been LOTS of theories as to the "cause" of it.
The nonlinear redshift-distance observations was predicted by
'non-believers'. (By the 'tired light' crowd.)
> Presumably, almost all of these are wrong.
Yes. And the cosmological constant theory is only one of the 'lots' of
theories, for which most will be wrong.
> I think one needs to separate the rather strong observational data from
> the large number of theoretical papers about possible "causes" of dark
> energy.
You mean from the possible 'causes' of the nonlinear redshift-distance
relationship.
"Dark energy" is a postulated cause of the observation. Dark energy is not
an observation.
> I have to admit my scepticism is increased by the fact that if
> the cosmological constant appears so "easily and naturally", why wasn't
> the paper published before the convincing observations were there?
On that we certainly agree.
--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail}
ebunn@lfa221051.richmond.edu
Jun11-04, 10:45 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 <10bpmpdbtk7518a@corp.supernews.com>,\ngreywolf4 2 <mingstb@marssim-ss.com> wrote:\n>\n>Phillip Helbig---remove CLOTHES to reply <helbig@astro.multiCLOTHESvax.de>\n>wrote in message news:c9aim0\\$cu\\$3@online.de...\n\n>> ALL the observational data are consistent with "dark energy" being the\n>> traditional cosmological constant.\n>\n>That\'s because the data all measure the same physical observable. The\n>nonlinearity of the redshift-distance relationship. It is this single\n>observable from which the "cosmological constant" is calculated.\n\nThis is false for two reasons.\n\n1. The evidence for dark energy does not come just from measurements\nof the distance-redshift relation. For example, the WMAP power\nspectrum (which shows that space is flat), combined with about two\ndecades worth of overwhelming observational evidence that the matter\ndensity is too low for a flat Universe, gives a measurement of the\ndark energy density that\'s completely independent of, but agrees\nastonishingly well with, the evidence from the distance-redshift\nrelation. Note that those lines of evidence have absolutely nothing\nto do with the distance-redshift relation: they depend on completely\ndifferent physics and probe completely different epochs.\n\n2. Even if you restrict your attention to the supernova\ndistance-redshift relation, it\'s not correct to describe the\nnonlinearity of this relation as a single observable. In the early\ndays of the field, such a description would have been arguably\naccurate, but not anymore. The theory predicts a function, not a\nnumber, and that function has now been measured over a wide enough\nrange of z that a one-parameter fit isn\'t good enough.\n\n>> This makes very concrete\n>> predictions: what the apparent magnitude of standard candles will be at\n>> redshifts where they have not yet been observed,\n>\n>These aren\'t predictions. The "CC" is back calculated from these very\n>items.\n\nThis is false. What Phillip wrote is precisely true. The\ncosmological constant was measured from supernova measurements (and\nstrongly confirmed by other observations). *After that*, the measured\nvalue has been used to make definite predictions about the magnitude\nof standard candles at higher redshifts that, as Phillip said, had not\nyet been observed. This is a testable prediction of the model. If it\ncomes out wrong, the model will be falsified.\n\n>> what the age of the universe is etc.\n>\n>I\'m not aware of a calculation of the age of the universe that rests upon\n>the assumption of the cosmological constant. Could you point me to a\n>reference?\n\nThe most widely-quoted number these days for the age of the Universe\ncomes from the first-year WMAP papers. The first paper at\n\nhttp://map.gsfc.nasa.gov/m_mm/pub_papers/firstyear.html\n\ngives the number. This age depends significantly on the value of the\ncosmological constant.\n\n\n-Ted\n\n\n--\n[E-mail me at name@domain.edu, as opposed to name@machine.domain.edu.]\n\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>In article <10bpmpdbtk7518a@corp.supernews.com>,
greywolf42 <mingstb@marssim-ss.com> wrote:
>
>Phillip Helbig---remove CLOTHES to reply <helbig@astro.multiCLOTHESvax.de>
>wrote in message news:c9aim0$cu$3@online.de...
>> ALL the observational data are consistent with "dark energy" being the
>> traditional cosmological constant.
>
>That's because the data all measure the same physical observable. The
>nonlinearity of the redshift-distance relationship. It is this single
>observable from which the "cosmological constant" is calculated.
This is false for two reasons.
1. The evidence for dark energy does not come just from measurements
of the distance-redshift relation. For example, the WMAP power
spectrum (which shows that space is flat), combined with about two
decades worth of overwhelming observational evidence that the matter
density is too low for a flat Universe, gives a measurement of the
dark energy density that's completely independent of, but agrees
astonishingly well with, the evidence from the distance-redshift
relation. Note that those lines of evidence have absolutely nothing
to do with the distance-redshift relation: they depend on completely
different physics and probe completely different epochs.
2. Even if you restrict your attention to the supernova
distance-redshift relation, it's not correct to describe the
nonlinearity of this relation as a single observable. In the early
days of the field, such a description would have been arguably
accurate, but not anymore. The theory predicts a function, not a
number, and that function has now been measured over a wide enough
range of z that a one-parameter fit isn't good enough.
>> This makes very concrete
>> predictions: what the apparent magnitude of standard candles will be at
>> redshifts where they have not yet been observed,
>
>These aren't predictions. The "CC" is back calculated from these very
>items.
This is false. What Phillip wrote is precisely true. The
cosmological constant was measured from supernova measurements (and
strongly confirmed by other observations). *After that*, the measured
value has been used to make definite predictions about the magnitude
of standard candles at higher redshifts that, as Phillip said, had not
yet been observed. This is a testable prediction of the model. If it
comes out wrong, the model will be falsified.
>> what the age of the universe is etc.
>
>I'm not aware of a calculation of the age of the universe that rests upon
>the assumption of the cosmological constant. Could you point me to a
>reference?
The most widely-quoted number these days for the age of the Universe
comes from the first-year WMAP papers. The first paper at
http://map.gsfc.nasa.gov/m_{mm}/pub_papers/firstyear.html
gives the number. This age depends significantly on the value of the
cosmological constant.
-Ted
--
[E-mail me at name@domain.edu, as opposed to name@machine.domain.edu.]
greywolf42
Jun13-04, 09:39 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><ebunn@lfa221051.richmond.edu> wrote in message\nnews:cacibo\\$vq0\\$1@lfa222122.richmond. edu...\n>\n> In article <10bpmpdbtk7518a@corp.supernews.com>,\n> greywolf42 <mingstb@marssim-ss.com> wrote:\n> >\n> >Phillip Helbig---remove CLOTHES to reply\n<helbig@astro.multiCLOTHESvax.de>\n> >wrote in message news:c9aim0\\$cu\\$3@online.de...\n>\n> >> ALL the observational data are consistent with "dark energy" being the\n> >> traditional cosmological constant.\n> >\n> >That\'s because the data all measure the same physical observable. The\n> >nonlinearity of the redshift-distance relationship. It is this single\n> >observable from which the "cosmological constant" is calculated.\n>\n> This is false for two reasons.\n>\n> 1. The evidence for dark energy does not come just from measurements\n> of the distance-redshift relation.\n\nAs we see below, this is not true. Distance-redshift is the only (current)\nsource for \'dark energy\' or \'cosmological constant.\'\n\n> For example, the WMAP power\n> spectrum (which shows that space is flat),\n\nThis might have some validity. Except for the following \'stuff\' that must\nbe combined into the mix:\n\n> combined with about two\n> decades worth of overwhelming observational evidence that the matter\n> density is too low for a flat Universe,\n\nThat is completely circular. The only \'flat universe\' that is ruled out by\nlow matter density is the theoretical BB universe.\n\n> gives a measurement of the\n> dark energy density that\'s completely independent of, but agrees\n> astonishingly well with, the evidence from the distance-redshift\n> relation.\n\nIt isn\'t astonishing at all, based on the information you give above and\nbelow. It is completely circular.\n\n> Note that those lines of evidence have absolutely nothing\n> to do with the distance-redshift relation: they depend on completely\n> different physics and probe completely different epochs.\n\nYour interpretations are completely circular.\n\n> 2. Even if you restrict your attention to the supernova\n> distance-redshift relation, it\'s not correct to describe the\n> nonlinearity of this relation as a single observable.\n\n\n[Moderator\'s note: As a curve consists of more than one point it encodes more\nthan one observable. -usc]\n\n\n> In the early\n> days of the field, such a description would have been arguably\n> accurate, but not anymore.\n\nThe length of time an observable is observed, does not change it\'s status as\nan observable.\n\n> The theory predicts a function, not a\n> number, and that function has now been measured over a wide enough\n> range of z that a one-parameter fit isn\'t good enough.\n\nTheory is irrelvant to whether something is an observable. Regardless of\nthe number of theoretical parameters used in the theory.\n\n> >> This makes very concrete\n> >> predictions: what the apparent magnitude of standard candles will be at\n> >> redshifts where they have not yet been observed,\n> >\n> >These aren\'t predictions. The "CC" is back calculated from these very\n> >items.\n>\n> This is false. What Phillip wrote is precisely true.\n\nI disagree. See below.\n\n> The\n> cosmological constant was measured from supernova measurements (and\n> strongly confirmed by other observations).\n\nThe cosmological constant is a theoretical parameter, and is not a direct\nobservable. One measures the redshift-distance curve, using supernovae (for\nexample).\n\n> *After that*, the measured\n> value has been used to make definite predictions about the magnitude\n> of standard candles at higher redshifts that, as Phillip said, had not\n> yet been observed. This is a testable prediction of the model. If it\n> comes out wrong, the model will be falsified.\n\nBut the curve has already been determined. (If it comes out *wrong* then\nthe SN curve is shown to have been in error.) It is in no way a testable\n*prediction* of the new, improved BB model (with dark energy).\n\nAdditional methods of measuring the redshift-distance relation simply\nvalidate (or invalidate) the SN method.\n\n> >> what the age of the universe is etc.\n> >\n> >I\'m not aware of a calculation of the age of the universe that rests upon\n> >the assumption of the cosmological constant. Could you point me to a\n> >reference?\n>\n> The most widely-quoted number these days for the age of the Universe\n> comes from the first-year WMAP papers. The first paper at\n>\n> http://map.gsfc.nasa.gov/m_mm/pub_papers/firstyear.html\n>\n> gives the number. This age depends significantly on the value of the\n> cosmological constant.\n\nBut the cosmological constant is first determined by the SN data curve! And\nthe assumption of the Big Bang. Which is already backfit onto the CMBR.\n\nThus, you have once again gone circular. Thus, it is not a surprise at all\nthat the WMAP data -- combined with BB parameters -- returns the BB\nparameters.\n\n--\ngreywolf42\nubi dubium ibi libertas\n{remove planet for return e-mail}\n\n\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><ebunn@lfa221051.richmond.edu> wrote in message
news:cacibo$vq0$1@lfa222122.richmond.edu...
>
> In article <10bpmpdbtk7518a@corp.supernews.com>,
> greywolf42 <mingstb@marssim-ss.com> wrote:
> >
> >Phillip Helbig---remove CLOTHES to reply
<helbig@astro.multiCLOTHESvax.de>
> >wrote in message news:c9aim0$cu$3@online.de...
>
> >> ALL the observational data are consistent with "dark energy" being the
> >> traditional cosmological constant.
> >
> >That's because the data all measure the same physical observable. The
> >nonlinearity of the redshift-distance relationship. It is this single
> >observable from which the "cosmological constant" is calculated.
>
> This is false for two reasons.
>
> 1. The evidence for dark energy does not come just from measurements
> of the distance-redshift relation.
As we see below, this is not true. Distance-redshift is the only (current)
source for 'dark energy' or 'cosmological constant.'
> For example, the WMAP power
> spectrum (which shows that space is flat),
This might have some validity. Except for the following 'stuff' that must
be combined into the mix:
> combined with about two
> decades worth of overwhelming observational evidence that the matter
> density is too low for a flat Universe,
That is completely circular. The only 'flat universe' that is ruled out by
low matter density is the theoretical BB universe.
> gives a measurement of the
> dark energy density that's completely independent of, but agrees
> astonishingly well with, the evidence from the distance-redshift
> relation.
It isn't astonishing at all, based on the information you give above and
below. It is completely circular.
> Note that those lines of evidence have absolutely nothing
> to do with the distance-redshift relation: they depend on completely
> different physics and probe completely different epochs.
Your interpretations are completely circular.
> 2. Even if you restrict your attention to the supernova
> distance-redshift relation, it's not correct to describe the
> nonlinearity of this relation as a single observable.
[Moderator's note: As a curve consists of more than one point it encodes more
than one observable. -usc]
> In the early
> days of the field, such a description would have been arguably
> accurate, but not anymore.
The length of time an observable is observed, does not change it's status as
an observable.
> The theory predicts a function, not a
> number, and that function has now been measured over a wide enough
> range of z that a one-parameter fit isn't good enough.
Theory is irrelvant to whether something is an observable. Regardless of
the number of theoretical parameters used in the theory.
> >> This makes very concrete
> >> predictions: what the apparent magnitude of standard candles will be at
> >> redshifts where they have not yet been observed,
> >
> >These aren't predictions. The "CC" is back calculated from these very
> >items.
>
> This is false. What Phillip wrote is precisely true.
I disagree. See below.
> The
> cosmological constant was measured from supernova measurements (and
> strongly confirmed by other observations).
The cosmological constant is a theoretical parameter, and is not a direct
observable. One measures the redshift-distance curve, using supernovae (for
example).
> *After that*, the measured
> value has been used to make definite predictions about the magnitude
> of standard candles at higher redshifts that, as Phillip said, had not
> yet been observed. This is a testable prediction of the model. If it
> comes out wrong, the model will be falsified.
But the curve has already been determined. (If it comes out *wrong* then
the SN curve is shown to have been in error.) It is in no way a testable
*prediction* of the new, improved BB model (with dark energy).
Additional methods of measuring the redshift-distance relation simply
validate (or invalidate) the SN method.
> >> what the age of the universe is etc.
> >
> >I'm not aware of a calculation of the age of the universe that rests upon
> >the assumption of the cosmological constant. Could you point me to a
> >reference?
>
> The most widely-quoted number these days for the age of the Universe
> comes from the first-year WMAP papers. The first paper at
>
> http://map.gsfc.nasa.gov/m_{mm}/pub_papers/firstyear.html
>
> gives the number. This age depends significantly on the value of the
> cosmological constant.
But the cosmological constant is first determined by the SN data curve! And
the assumption of the Big Bang. Which is already backfit onto the CMBR.
Thus, you have once again gone circular. Thus, it is not a surprise at all
that the WMAP data -- combined with BB parameters -- returns the BB
parameters.
--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail}
Phillip Helbig---remove CLOTHES to reply
Jun14-04, 03:31 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 <10cmidvkitdv22e@corp.supernews.com>, "greywolf42"\n<mingstb@marssim-ss.com> writes:\n\n> > 1. The evidence for dark energy does not come just from measurements\n> > of the distance-redshift relation.\n>\n> As we see below, this is not true. Distance-redshift is the only (current)\n> source for \'dark energy\' or \'cosmological constant.\'\n>\n> > For example, the WMAP power\n> > spectrum (which shows that space is flat),\n>\n> This might have some validity. Except for the following \'stuff\' that must\n> be combined into the mix:\n>\n> > combined with about two\n> > decades worth of overwhelming observational evidence that the matter\n> > density is too low for a flat Universe,\n>\n> That is completely circular. The only \'flat universe\' that is ruled out by\n> low matter density is the theoretical BB universe.\n\nCan you define the "theoretical BB universe", explain why you call it\nthat, and provide some context so that it is clear that it is not some\nsort of straw man developed mainly for the argument here?\n\n> > gives a measurement of the\n> > dark energy density that\'s completely independent of, but agrees\n> > astonishingly well with, the evidence from the distance-redshift\n> > relation.\n>\n> It isn\'t astonishing at all, based on the information you give above and\n> below. It is completely circular.\n\nThis is just plain wrong. One can calculate Omega and lambda from the\nsupernovae data alone. One can measure Omega directly. One can measure\nthe sum of Omega and lambda from the CMB. These three measurements,\nmathematically, don\'t have to be consistent, i.e. there is not\nautomatically a value for lambda and Omega which satisfies all\nmeasurements, but observationally there is. Explain the circularity.\n\n> > 2. Even if you restrict your attention to the supernova\n> > distance-redshift relation, it\'s not correct to describe the\n> > nonlinearity of this relation as a single observable.\n>\n> > In the early\n> > days of the field, such a description would have been arguably\n> > accurate, but not anymore.\n>\n> The length of time an observable is observed, does not change it\'s status as\n> an observable.\n\nI think it is obvious to all readers now that you don\'t understand the\nlogic. The point is not that an observable is somehow different just\nbecause one observes it longer, but rather that more and better\nobservations show a curve which needs more than one parameter to fit it.\nWith a single parameter, there is room for degeneracy; with two\nparameters, much less room.\n\n> > >> This makes very concrete\n> > >> predictions: what the apparent magnitude of standard candles will be at\n> > >> redshifts where they have not yet been observed,\n> > >\n> > >These aren\'t predictions. The "CC" is back calculated from these very\n> > >items.\n> >\n> > This is false. What Phillip wrote is precisely true.\n>\n> I disagree. See below.\n>\n> > The\n> > cosmological constant was measured from supernova measurements (and\n> > strongly confirmed by other observations).\n>\n> The cosmological constant is a theoretical parameter, and is not a direct\n> observable. One measures the redshift-distance curve, using supernovae (for\n> example).\n\nYou are playing with words. If I measure the voltage in my car battery,\nI see a needle moving across a scale, or some LCD numbers appear in a\ndisplay. What\'s your point?\n\n> > *After that*, the measured\n> > value has been used to make definite predictions about the magnitude\n> > of standard candles at higher redshifts that, as Phillip said, had not\n> > yet been observed. This is a testable prediction of the model. If it\n> > comes out wrong, the model will be falsified.\n>\n> But the curve has already been determined. (If it comes out *wrong* then\n> the SN curve is shown to have been in error.) It is in no way a testable\n> *prediction* of the new, improved BB model (with dark energy).\n\nThis is complete rubbish, not because I say so, but because your\nstatement is plainly and simply not true. Give me some references which\ndemonstrate that the "curve has already been determined".\n\n> > >I\'m not aware of a calculation of the age of the universe that rests upon\n> > >the assumption of the cosmological constant. Could you point me to a\n> > >reference?\n> >\n> > The most widely-quoted number these days for the age of the Universe\n> > comes from the first-year WMAP papers. The first paper at\n> >\n> > http://map.gsfc.nasa.gov/m_mm/pub_papers/firstyear.html\n> >\n> > gives the number. This age depends significantly on the value of the\n> > cosmological constant.\n>\n> But the cosmological constant is first determined by the SN data curve! And\n> the assumption of the Big Bang. Which is already backfit onto the CMBR.\n\nAgain, this statement shows that you don\'t even understand the argument.\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 <10cmidvkitdv22e@corp.supernews.com>, "greywolf42"
<mingstb@marssim-ss.com> writes:
> > 1. The evidence for dark energy does not come just from measurements
> > of the distance-redshift relation.
>
> As we see below, this is not true. Distance-redshift is the only (current)
> source for 'dark energy' or 'cosmological constant.'
>
> > For example, the WMAP power
> > spectrum (which shows that space is flat),
>
> This might have some validity. Except for the following 'stuff' that must
> be combined into the mix:
>
> > combined with about two
> > decades worth of overwhelming observational evidence that the matter
> > density is too low for a flat Universe,
>
> That is completely circular. The only 'flat universe' that is ruled out by
> low matter density is the theoretical BB universe.
Can you define the "theoretical BB universe", explain why you call it
that, and provide some context so that it is clear that it is not some
sort of straw man developed mainly for the argument here?
> > gives a measurement of the
> > dark energy density that's completely independent of, but agrees
> > astonishingly well with, the evidence from the distance-redshift
> > relation.
>
> It isn't astonishing at all, based on the information you give above and
> below. It is completely circular.
This is just plain wrong. One can calculate \Omega and \lambda from the
supernovae data alone. One can measure \Omega directly. One can measure
the sum of \Omega and \lambda from the CMB. These three measurements,
mathematically, don't have to be consistent, i.e. there is not
automatically a value for \lambda and \Omega which satisfies all
measurements, but observationally there is. Explain the circularity.
> > 2. Even if you restrict your attention to the supernova
> > distance-redshift relation, it's not correct to describe the
> > nonlinearity of this relation as a single observable.
>
> > In the early
> > days of the field, such a description would have been arguably
> > accurate, but not anymore.
>
> The length of time an observable is observed, does not change it's status as
> an observable.
I think it is obvious to all readers now that you don't understand the
logic. The point is not that an observable is somehow different just
because one observes it longer, but rather that more and better
observations show a curve which needs more than one parameter to fit it.
With a single parameter, there is room for degeneracy; with two
parameters, much less room.
> > >> This makes very concrete
> > >> predictions: what the apparent magnitude of standard candles will be at
> > >> redshifts where they have not yet been observed,
> > >
> > >These aren't predictions. The "CC" is back calculated from these very
> > >items.
> >
> > This is false. What Phillip wrote is precisely true.
>
> I disagree. See below.
>
> > The
> > cosmological constant was measured from supernova measurements (and
> > strongly confirmed by other observations).
>
> The cosmological constant is a theoretical parameter, and is not a direct
> observable. One measures the redshift-distance curve, using supernovae (for
> example).
You are playing with words. If I measure the voltage in my car battery,
I see a needle moving across a scale, or some LCD numbers appear in a
display. What's your point?
> > *After that*, the measured
> > value has been used to make definite predictions about the magnitude
> > of standard candles at higher redshifts that, as Phillip said, had not
> > yet been observed. This is a testable prediction of the model. If it
> > comes out wrong, the model will be falsified.
>
> But the curve has already been determined. (If it comes out *wrong* then
> the SN curve is shown to have been in error.) It is in no way a testable
> *prediction* of the new, improved BB model (with dark energy).
This is complete rubbish, not because I say so, but because your
statement is plainly and simply not true. Give me some references which
demonstrate that the "curve has already been determined".
> > >I'm not aware of a calculation of the age of the universe that rests upon
> > >the assumption of the cosmological constant. Could you point me to a
> > >reference?
> >
> > The most widely-quoted number these days for the age of the Universe
> > comes from the first-year WMAP papers. The first paper at
> >
> > http://map.gsfc.nasa.gov/m_{mm}/pub_papers/firstyear.html
> >
> > gives the number. This age depends significantly on the value of the
> > cosmological constant.
>
> But the cosmological constant is first determined by the SN data curve! And
> the assumption of the Big Bang. Which is already backfit onto the CMBR.
Again, this statement shows that you don't even understand the argument.
greywolf42
Jun16-04, 03:57 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>[Moderator\'s note: This discussion is getting (a) repetitive and (b)\ntesty in tone. Everyone involved should think carefully about\nwhether there\'s significant additional physics content to be added\nbefore deciding to continue. -TB]\n\n\nPhillip Helbig---remove CLOTHES to reply <helbig@astro.multiCLOTHESvax.de>\nwrote in message news:caijfu\\$c49\\$2@online.de...\n>\n> In article <10cmidvkitdv22e@corp.supernews.com>, "greywolf42"\n> <mingstb@marssim-ss.com> writes:\n>\n> > > 1. The evidence for dark energy does not come just from measurements\n> > > of the distance-redshift relation.\n> >\n> > As we see below, this is not true. Distance-redshift is the only\n> > (current) source for \'dark energy\' or \'cosmological constant.\'\n> >\n> > > For example, the WMAP power\n> > > spectrum (which shows that space is flat),\n> >\n> > This might have some validity. Except for the following \'stuff\' that\n> > must be combined into the mix:\n> >\n> > > combined with about two\n> > > decades worth of overwhelming observational evidence that the matter\n> > > density is too low for a flat Universe,\n> >\n> > That is completely circular. The only \'flat universe\' that is ruled out\n> > by low matter density is the theoretical BB universe.\n>\n> Can you define the "theoretical BB universe",\n\nThe universe that the BB theory predicts.\n\n> explain why you call it that, and provide some context so that it is clear\nthat it is not some\n> sort of straw man developed mainly for the argument here?\n\n1) You made the claim that a \'flat universe\' is ruled out by low matter\ndensity.\n2) I pointed out that this claim of yours rests solely on the predictions of\nthe BB.\n\n> > > gives a measurement of the\n> > > dark energy density that\'s completely independent of, but agrees\n> > > astonishingly well with, the evidence from the distance-redshift\n> > > relation.\n> >\n> > It isn\'t astonishing at all, based on the information you give above and\n> > below. It is completely circular.\n>\n> This is just plain wrong. One can calculate Omega and lambda from the\n> supernovae data alone.\n\nBut these are theoretical parameters, belonging to the BB. The supernovae\ndata are observations.\n\n> One can measure Omega directly.\n\nHow, specifcally?\n\n> One can measure\n> the sum of Omega and lambda from the CMB.\n\nOne can *calculate* omega and lambda from the BB theory. But they aren\'t\nobservables, or measurables.\n\n> These three measurements,\n> mathematically, don\'t have to be consistent, i.e. there is not\n> automatically a value for lambda and Omega which satisfies all\n> measurements, but observationally there is. Explain the circularity.\n\nAlready shown, in the prior post. The circularity is in the calculation of\nthe numbers.\n\n> > > 2. Even if you restrict your attention to the supernova\n> > > distance-redshift relation, it\'s not correct to describe the\n> > > nonlinearity of this relation as a single observable.\n> >\n> > > In the early\n> > > days of the field, such a description would have been arguably\n> > > accurate, but not anymore.\n> >\n> > The length of time an observable is observed, does not change it\'s\n> > status as an observable.\n>\n> I think it is obvious to all readers now that you don\'t understand the\n> logic.\n\nI think it is clear to all readers now, that you cannot post a paragraph\nwithout a leading ad hominem.\n\n> The point is not that an observable is somehow different just\n> because one observes it longer, but rather that more and better\n> observations show a curve which needs more than one parameter to fit it.\n> With a single parameter, there is room for degeneracy; with two\n> parameters, much less room.\n\nYour *parameters* are theoretical components of a theory. The \'one\nparameter\' vs \'two parameter\' argument is irrelevant. Either the BB only\nalways had two parameters, or it one parameter ... or you are discussing two\ndifferent theories.\n\n{snip uncommented section}\n> >\n> > > The\n> > > cosmological constant was measured from supernova measurements (and\n> > > strongly confirmed by other observations).\n> >\n> > The cosmological constant is a theoretical parameter, and is not a\n> > direct observable. One measures the redshift-distance curve, using\n> > supernovae (for example).\n>\n> You are playing with words. If I measure the voltage in my car battery,\n> I see a needle moving across a scale, or some LCD numbers appear in a\n> display. What\'s your point?\n\nGiven quite clearly above. I made no allusion whatever about using analog\nvs. digital measuring devices.\n\n> > > *After that*, the measured\n> > > value has been used to make definite predictions about the magnitude\n> > > of standard candles at higher redshifts that, as Phillip said, had not\n> > > yet been observed. This is a testable prediction of the model. If it\n> > > comes out wrong, the model will be falsified.\n> >\n> > But the curve has already been determined. (If it comes out *wrong*\n> > then the SN curve is shown to have been in error.) It is in no way a\n> > testable *prediction* of the new, improved BB model (with dark energy).\n>\n> This is complete rubbish, not because I say so, but because your\n> statement is plainly and simply not true. Give me some references which\n> demonstrate that the "curve has already been determined".\n\nSee your prior statements.\n\n> > > >I\'m not aware of a calculation of the age of the universe that rests\n> > > >upon the assumption of the cosmological constant. Could you\n> > > >point me to a reference?\n> > >\n> > > The most widely-quoted number these days for the age of the Universe\n> > > comes from the first-year WMAP papers. The first paper at\n> > >\n> > > http://map.gsfc.nasa.gov/m_mm/pub_papers/firstyear.html\n> > >\n> > > gives the number. This age depends significantly on the value of the\n> > > cosmological constant.\n> >\n> > But the cosmological constant is first determined by the SN data curve!\n> > And the assumption of the Big Bang. Which is already backfit onto the\n> > CMBR.\n>\n> Again, this statement shows that you don\'t even understand the argument.\n\nWhen you can\'t refute, insult!\n\n--\ngreywolf42\nubi dubium ibi libertas\n{remove planet for return e-mail}\n\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>[Moderator's note: This discussion is getting (a) repetitive and (b)
testy in tone. Everyone involved should think carefully about
whether there's significant additional physics content to be added
before deciding to continue. -TB]
Phillip Helbig---remove CLOTHES to reply <helbig@astro.multiCLOTHESvax.de>
wrote in message news:caijfu$c49$2@online.de...
>
> In article <10cmidvkitdv22e@corp.supernews.com>, "greywolf42"
> <mingstb@marssim-ss.com> writes:
>
> > > 1. The evidence for dark energy does not come just from measurements
> > > of the distance-redshift relation.
> >
> > As we see below, this is not true. Distance-redshift is the only
> > (current) source for 'dark energy' or 'cosmological constant.'
> >
> > > For example, the WMAP power
> > > spectrum (which shows that space is flat),
> >
> > This might have some validity. Except for the following 'stuff' that
> > must be combined into the mix:
> >
> > > combined with about two
> > > decades worth of overwhelming observational evidence that the matter
> > > density is too low for a flat Universe,
> >
> > That is completely circular. The only 'flat universe' that is ruled out
> > by low matter density is the theoretical BB universe.
>
> Can you define the "theoretical BB universe",
The universe that the BB theory predicts.
> explain why you call it that, and provide some context so that it is clear
that it is not some
> sort of straw man developed mainly for the argument here?
1) You made the claim that a 'flat universe' is ruled out by low matter
density.
2) I pointed out that this claim of yours rests solely on the predictions of
the BB.
> > > gives a measurement of the
> > > dark energy density that's completely independent of, but agrees
> > > astonishingly well with, the evidence from the distance-redshift
> > > relation.
> >
> > It isn't astonishing at all, based on the information you give above and
> > below. It is completely circular.
>
> This is just plain wrong. One can calculate \Omega and \lambda from the
> supernovae data alone.
But these are theoretical parameters, belonging to the BB. The supernovae
data are observations.
> One can measure \Omega directly.
How, specifcally?
> One can measure
> the sum of \Omega and \lambda from the CMB.
One can *calculate* \omega and \lambda from the BB theory. But they aren't
observables, or measurables.
> These three measurements,
> mathematically, don't have to be consistent, i.e. there is not
> automatically a value for \lambda and \Omega which satisfies all
> measurements, but observationally there is. Explain the circularity.
Already shown, in the prior post. The circularity is in the calculation of
the numbers.
> > > 2. Even if you restrict your attention to the supernova
> > > distance-redshift relation, it's not correct to describe the
> > > nonlinearity of this relation as a single observable.
> >
> > > In the early
> > > days of the field, such a description would have been arguably
> > > accurate, but not anymore.
> >
> > The length of time an observable is observed, does not change it's
> > status as an observable.
>
> I think it is obvious to all readers now that you don't understand the
> logic.
I think it is clear to all readers now, that you cannot post a paragraph
without a leading ad hominem.
> The point is not that an observable is somehow different just
> because one observes it longer, but rather that more and better
> observations show a curve which needs more than one parameter to fit it.
> With a single parameter, there is room for degeneracy; with two
> parameters, much less room.
Your *parameters* are theoretical components of a theory. The 'one
parameter' vs 'two parameter' argument is irrelevant. Either the BB only
always had two parameters, or it one parameter ... or you are discussing two
different theories.
{snip uncommented section}
> >
> > > The
> > > cosmological constant was measured from supernova measurements (and
> > > strongly confirmed by other observations).
> >
> > The cosmological constant is a theoretical parameter, and is not a
> > direct observable. One measures the redshift-distance curve, using
> > supernovae (for example).
>
> You are playing with words. If I measure the voltage in my car battery,
> I see a needle moving across a scale, or some LCD numbers appear in a
> display. What's your point?
Given quite clearly above. I made no allusion whatever about using analog
vs. digital measuring devices.
> > > *After that*, the measured
> > > value has been used to make definite predictions about the magnitude
> > > of standard candles at higher redshifts that, as Phillip said, had not
> > > yet been observed. This is a testable prediction of the model. If it
> > > comes out wrong, the model will be falsified.
> >
> > But the curve has already been determined. (If it comes out *wrong*
> > then the SN curve is shown to have been in error.) It is in no way a
> > testable *prediction* of the new, improved BB model (with dark energy).
>
> This is complete rubbish, not because I say so, but because your
> statement is plainly and simply not true. Give me some references which
> demonstrate that the "curve has already been determined".
See your prior statements.
> > > >I'm not aware of a calculation of the age of the universe that rests
> > > >upon the assumption of the cosmological constant. Could you
> > > >point me to a reference?
> > >
> > > The most widely-quoted number these days for the age of the Universe
> > > comes from the first-year WMAP papers. The first paper at
> > >
> > > http://map.gsfc.nasa.gov/m_{mm}/pub_papers/firstyear.html
> > >
> > > gives the number. This age depends significantly on the value of the
> > > cosmological constant.
> >
> > But the cosmological constant is first determined by the SN data curve!
> > And the assumption of the Big Bang. Which is already backfit onto the
> > CMBR.
>
> Again, this statement shows that you don't even understand the argument.
When you can't refute, insult!
--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail}
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