View Full Version : DARK ENERGY
alistair
Jun4-04, 02:47 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> 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> > 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>"" (read: " CDM") is the shorthand for the cosmological model\n>which includes a cosmological constant (capital as well as cold dark\n>matter (in addition to the ordinary matter) which has been\nspectacularly\n>confirmed by recent experimental data. For more information on this\nissue\n>there is a very nice review by Sean Carroll\n\n>http://pancake.uchicago.edu/~carroll/preposterous.html .\n\n>Everybody trying to challenge widely accepted results is well advised\nto\n>first acquaint himself with the theory in question.\n\nALISTAIR writes:\n\nSean Carroll says on the website Urs Schreiber listed:\n\n"So the approximate coincidence we observe today between the amount of\ndark energy and the amount of matter is a short-lived one\n(cosmologically speaking) -- earlier on, the matter was dominating,\nand before too long (a few billion years) the dark energy will have\ncompletely taken over"\n\nWe know that less dark matter would make the distribution of stars in\ngalaxies different (perhaps the stars would have too high a velocity\nto stay together in a galaxy)and so would more dark matter.This would\naffect the evolution of galaxies and so life would not necessarily be\npresent in the universe now.\nIf dark matter turns out to be dark energy ( as some theorists are\nsaying)\nthen it would not be so surprising that living beings exist when the\ndark energy/dark matter/normal baryonic matter relative abundance is\nwhat we are currently observing.In fact, this could be used as an\nargument in favour of dark energy being dark matter.\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
> > 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.
>"" (read: " CDM") is the shorthand for the cosmological model
>which includes a cosmological constant (capital 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.
ALISTAIR writes:
Sean Carroll says on the website Urs Schreiber listed:
"So the approximate coincidence we observe today between the amount of
dark energy and the amount of matter is a short-lived one
(cosmologically speaking) -- earlier on, the matter was dominating,
and before too long (a few billion years) the dark energy will have
completely taken over"
We know that less dark matter would make the distribution of stars in
galaxies different (perhaps the stars would have too high a velocity
to stay together in a galaxy)and so would more dark matter.This would
affect the evolution of galaxies and so life would not necessarily be
present in the universe now.
If dark matter turns out to be dark energy ( as some theorists are
saying)
then it would not be so surprising that living beings exist when the
dark energy/dark matter/normal baryonic matter relative abundance is
what we are currently observing.In fact, this could be used as an
argument in favour of dark energy being dark matter.
Thomas Dent
Jun4-04, 02:48 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\n\n> People investigate cold versus hot dark matter. I don\'t know\n> about the issue of temperature for dark energy, but at this point,\n> anyone is free to speculate.\n\nNo, you are not free to speculate something that is at odds with data.\nHot dark matter has been shown to produce the wrong results for\nstructure formation - it smooths out fluctuations on small scales so\nthat it would be impossible to form galaxies early on in the Universe.\n\nGalaxy surveys tell you about structure formation, which in turn tells\nyou something about dark matter, which has already ruled out many of\nthe scenarios.\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.\n\nSo why isn\'t there someone who can play a perfect game of chess? Why\nhasn\'t anyone composed Beethoven\'s Sixth Piano Concerto? Some things\nare just *hard*.\n\n> If there was a solution in an area of study, one of these brilliantly\n> bright people should have found it already.\n\nThis is a complete non sequitur. Fifty years ago the number of bright\npeople in astrophysics/cosmology wasn\'t so very different from what it\nis now, yet they hadn\'t "got the solution" then.\n\nWhat sort of bizarre attitude is it to say, unless science can give us\nthe solution right now, it is obviously on the wrong track? For one\nthing, the data aren\'t nearly good enough to really tell us what\'s\ngoing on. You can\'t blame theorists for that.\n\n> We are trying to explain the behaviour of simple, dead stupid matter.\n\nActually, we\'re trying to explain the behaviour of *space*, which is\nrather less than simple, especially in G.R.\n\n> The math for gravity should be a wee bit simpler than EM since they are\n> so darn similar classically.\n\nIf you think GR has simple math then you\'re a lucky man. Gravity is\nabout twice as difficult (having a tensor field not a vector) and\nquantum gravity several orders of magnitude more difficult.\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
> 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.
No, you are not free to speculate something that is at odds with data.
Hot dark matter has been shown to produce the wrong results for
structure formation - it smooths out fluctuations on small scales so
that it would be impossible to form galaxies early on in the Universe.
Galaxy surveys tell you about structure formation, which in turn tells
you something about dark matter, which has already ruled out many of
the scenarios.
> 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.
So why isn't there someone who can play a perfect game of chess? Why
hasn't anyone composed Beethoven's Sixth Piano Concerto? Some things
are just *hard*.
> If there was a solution in an area of study, one of these brilliantly
> bright people should have found it already.
This is a complete non sequitur. Fifty years ago the number of bright
people in astrophysics/cosmology wasn't so very different from what it
is now, yet they hadn't "got the solution" then.
What sort of bizarre attitude is it to say, unless science can give us
the solution right now, it is obviously on the wrong track? For one
thing, the data aren't nearly good enough to really tell us what's
going on. You can't blame theorists for that.
> We are trying to explain the behaviour of simple, dead stupid matter.
Actually, we're trying to explain the behaviour of *space*, which is
rather less than simple, especially in G.R.
> The math for gravity should be a wee bit simpler than EM since they are
> so darn similar classically.
If you think GR has simple math then you're a lucky man. Gravity is
about twice as difficult (having a tensor field not a vector) and
quantum gravity several orders of magnitude more difficult.
Phillip Helbig---remove CLOTHES to reply
Jun7-04, 04:54 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>\n\n"greywolf42" <mingstb@marssim-ss.com> writes:\n\n> Phillip Helbig---remove CLOTHES to reply <helbig@astro.multiCLOTHESvax.de>\n> wrote 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>\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 true to some extent, but it would be going too far to say that\nALL THE DATA measure the same physical observable. Classical\ncosmological tests, sure, but in the case of the CMB, only in a very\nroundabout way.\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 just plain wrong, though one could think that perhaps I was a\nbit unclear. Based on your previous posts, however, it is clear to me\nthat you know exactly what I meant: One observes, say, the\napparent-magnitude--redshift relation over a certain range of redshift,\ncalculates the cosmological parameters, then PREDICTS what this\nrelationship will be AT LARGER REDSHIFT. In particular, the "new\nstandard model" has standard candles appearing fainter at moderate\nredshift, but at larger redshift they get brighter again. This pretty\nmuch rules out alternative models for the faintness at lower redshift,\nsuch as dust causing darkening (which is ruled out by other arguments as\nwell, such as the fact that the darkening is wavelength-independent\nwhile all known dust also causes reddening, leading to the more-or-less\nad hoc "grey dust" hypothesis).\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\nCome on. Look in a cosmology textbook. Calculating the age of the\nuniverse for given cosmological parameters is basic textbook stuff. I\nthink the age of the universe based on the latest cosmological\nparameters from WMAP was even in the New York Times. Tables were\npublished covering a wide range of parameters (even the current new\nstandard model) almost 40 years ago.\n\nReference?\n\n@ARTICLE {SRefsdalSdL67a,\nAUTHOR = "Sjur Refsdal and Rolf Stabell and\nF. G. de Lange",\nTITLE = "Numerical calculations on relativistic\ncosmological models",\nJOURNAL = MRAS,\nYEAR = "1967",\nVOLUME = "71",\nPAGES = "143"\n}\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>\n> The nonlinear redshift-distance observations was predicted by\n> \'non-believers\'. (By the \'tired light\' crowd.)\n\nCompletely wrong. Tired light has always been an ad-hoc theory to\nexplain redshift. I think you should point out a reference where this is\npredicted from first principles.\n\n> > Presumably, almost all of these are wrong.\n>\n> Yes. And the cosmological constant theory is only one of the \'lots\' of\n> theories, for which most will be wrong.\n\nDon\'t play with words. I carefully pointed out the difference\nbetween the observation of the cosmological constant as a relatively\nsecure fact, and more speculative theories as to its origin. If you\nmean the latter, then there is no one "cosmological constant theory"; if\nyou mean the former, then you are disputing the data but claiming to be\ndisputing "a theory" or "the theory". (This is similar to arguments\nused by creationists disputing evolution: they point out (real or\nimagined or misinterpreted) debates about the MECHANISM of evolution\namong biologists and try to bend this to cast doubt on the OBSERVATION\nthat evolution has occurred.)\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>\n> You mean from the possible \'causes\' of the nonlinear redshift-distance\n> relationship.\n>\n> "Dark energy" is a postulated cause of the observation. Dark energy is not\n> an observation.\n\nAgain, playing with words. If you are questioning things at this level,\nyou need to present a complete theory which explains the nonlinearity of\nthe redshift-distance relation outside the context of standard cosmology.\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>"greywolf42" <mingstb@marssim-ss.com> writes:
> 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 is true to some extent, but it would be going too far to say that
ALL THE DATA measure the same physical observable. Classical
cosmological tests, sure, but in the case of the CMB, only in a very
roundabout way.
> > 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 just plain wrong, though one could think that perhaps I was a
bit unclear. Based on your previous posts, however, it is clear to me
that you know exactly what I meant: One observes, say, the
apparent-magnitude--redshift relation over a certain range of redshift,
calculates the cosmological parameters, then PREDICTS what this
relationship will be AT LARGER REDSHIFT. In particular, the "new
standard model" has standard candles appearing fainter at moderate
redshift, but at larger redshift they get brighter again. This pretty
much rules out alternative models for the faintness at lower redshift,
such as dust causing darkening (which is ruled out by other arguments as
well, such as the fact that the darkening is wavelength-independent
while all known dust also causes reddening, leading to the more-or-less
ad hoc "grey dust" hypothesis).
> > 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?
Come on. Look in a cosmology textbook. Calculating the age of the
universe for given cosmological parameters is basic textbook stuff. I
think the age of the universe based on the latest cosmological
parameters from WMAP was even in the New York Times. Tables were
published covering a wide range of parameters (even the current new
standard model) almost 40 years ago.
Reference?
@ARTICLE {SRefsdalSdL67a,
AUTHOR = "Sjur Refsdal and Rolf Stabell and
F. G. de Lange",
TITLE = "Numerical calculations on relativistic
cosmological models",
JOURNAL = MRAS,
YEAR = "1967",
VOLUME = "71",
PAGES = "143"
}
> > > 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.)
Completely wrong. Tired light has always been an ad-hoc theory to
explain redshift. I think you should point out a reference where this is
predicted from first principles.
> > 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.
Don't play with words. I carefully pointed out the difference
between the observation of the cosmological constant as a relatively
secure fact, and more speculative theories as to its origin. If you
mean the latter, then there is no one "cosmological constant theory"; if
you mean the former, then you are disputing the data but claiming to be
disputing "a theory" or "the theory". (This is similar to arguments
used by creationists disputing evolution: they point out (real or
imagined or misinterpreted) debates about the MECHANISM of evolution
among biologists and try to bend this to cast doubt on the OBSERVATION
that evolution has occurred.)
> > 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.
Again, playing with words. If you are questioning things at this level,
you need to present a complete theory which explains the nonlinearity of
the redshift-distance relation outside the context of standard cosmology.
Phillip Helbig---remove CLOTHES to reply
Jun7-04, 04:54 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>\n\nIn article <861c1b21.0406011259.29daa479@posting.google.com>, \nalistair@goforit64.fsnet.co.uk (alistair) writes:\n\n> If dark matter turns out to be dark energy ( as some theorists are\n> saying)\n> then it would not be so surprising that living beings exist when the\n> dark energy/dark matter/normal baryonic matter relative abundance is\n> what we are currently observing.In fact, this could be used as an\n> argument in favour of dark energy being dark matter.\n\nNo theorist is saying this, at least in the sense you imply above. If\ndark energy literally WERE dark matter, then there would be no need to\ncall it something else.\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 <861c1b21.0406011259.29daa479@posting.google.com>,
alistair@goforit64.fsnet.co.uk (alistair) writes:
> If dark matter turns out to be dark energy ( as some theorists are
> saying)
> then it would not be so surprising that living beings exist when the
> dark energy/dark matter/normal baryonic matter relative abundance is
> what we are currently observing.In fact, this could be used as an
> argument in favour of dark energy being dark matter.
No theorist is saying this, at least in the sense you imply above. If
dark energy literally WERE dark matter, then there would be no need to
call it something else.
alistair
Jun7-04, 04:54 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>\ntdent@auth.gr (Thomas Dent) wrote in message news:<cb504c2c.0406020621.7a82ccea@posting.google. com>...\n> Doug Sweetser <sweetser@alum.mit.edu> wrote\n\n> If you think GR has simple math then you\'re a lucky man. Gravity is\n> about twice as difficult (having a tensor field not a vector) and\n> quantum gravity several orders of magnitude more difficult.\n\n\nALISTAIR writes:\n\nThere is no proof that Quantum gravity, if it is a real phenomenon,\nhas to be mathematically or conceptually difficult.One day, the\ngravitational field may be quantised without reference to\nmathematically difficult theories like qed and general relativity.Who\nknows!If you look at the thread on sci.physics.research "quantizing\ngravity" you will see discussion of ideas\nsuch as "what does it mean to quantize gravity?" Apparently there is\nnot even\nagreement on this in the physics community and apparently there is no\nagreement on what it means to quantize anything?!!\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>tdent@auth.gr (Thomas Dent) wrote in message news:<cb504c2c.0406020621.7a82ccea@posting.google.com>...
> Doug Sweetser <sweetser@alum.mit.edu> wrote
> If you think GR has simple math then you're a lucky man. Gravity is
> about twice as difficult (having a tensor field not a vector) and
> quantum gravity several orders of magnitude more difficult.
ALISTAIR writes:
There is no proof that Quantum gravity, if it is a real phenomenon,
has to be mathematically or conceptually difficult.One day, the
gravitational field may be quantised without reference to
mathematically difficult theories like qed and general relativity.Who
knows!If you look at the thread on sci.physics.research "quantizing
gravity" you will see discussion of ideas
such as "what does it mean to quantize gravity?" Apparently there is
not even
agreement on this in the physics community and apparently there is no
agreement on what it means to quantize anything?!!
vBulletin® v3.8.7, Copyright ©2000-2012, vBulletin Solutions, Inc.