Does Cold Dark Matter Radiate 2.73K Heat?
Chalky
perfectly black bodies radiate and absorb heat according to well known
laws, isn't it likely that cold dark matter will radiate heat with a
2.73K black body spectrum?
I realise that CDM is only meant to interact gravitationally, but,
afaict, that is merely because it has only been postulated to 'balance
the (gravitational) books' . However, either in the form of MACHOS or
WIMPS, I can't see how it could fail to obey black body radiation
laws.
Would this create any problems astrophysically?
[[Mod. note -- I think the key defining characteristic of dark matter
is that it's "dark", i.e., it doesn't interact via the strong, weak,
or electromagnetic forces. Not interacting electromagnetically
implies that dark matter neither absorbs nor emits thermal
(black-body) radiation.
It's not quite the same, but you can get a mildly-useful approximation
to the properties of dark matter by thinking of it as a dilute gas of
neutrinos. I wouldn't exprect these to have much in the way of
black-body radiation or absorption, either...
-- jt]]
eric gisse
> Given that you can't get any darker than perfectly black, and
> perfectly black bodies radiate and absorb heat according to well known
> laws, isn't it likely that cold dark matter will radiate heat with a
> 2.73K black body spectrum?
>
> I realise that CDM is only meant to interact gravitationally, but,
> afaict, that is merely because it has only been postulated to 'balance
> the (gravitational) books' . However, either in the form of MACHOS or
> WIMPS, I can't see how it could fail to obey black body radiation
> laws.
>
> Would this create any problems astrophysically?
Only if you consider asking how to make matter with no electromagnetic
interaction interact electromagnetically a problem.
jw...@basicisp.net
> Given that you can't get any darker than perfectly black, and
> perfectly black bodies radiate and absorb heat according to well known
> laws, isn't it likely that cold dark matter will radiate heat with a
> 2.73K black body spectrum?
>
At absolute zero, there is no molecular energy to be converted to
microwaves, so I wouls say, no. There is no heat to be radiated.
Also, when one writes "perfectly black", one doesn't refer to
black color; one refers to the spectral distribution of light at
all wavelengths (this is the "Planck radiator" spectrum). For
example, a glowing hot coal could have very close to a perfect
"black body" spectrum and yet be easily visible.
Also, "cold dark matter" can't, so far as I know, be distinguished
from thinly-distributed, baseball-sized lumps of rock at or below
radiative equilibrium with the CMB. We don't know what it
is -- it may be anything, including neutrinos or other particles
which don't radiate unless they collide with something.
Phillip Helbig---undress to reply
<c4c2bad1-a35c-4911...@a6g2000yqm.googlegroups.com>,
"jw...@BasicISP.net" <jw...@BasicISP.net> writes:
> Also, "cold dark matter" can't, so far as I know, be distinguished
> from thinly-distributed, baseball-sized lumps of rock at or below
> radiative equilibrium with the CMB.
Observationally, no, at least not yet. However, such "bricks" or
whatever cannot be baryonic, due to constraints from nucleosynthesis.
> We don't know what it
> is -- it may be anything, including neutrinos or other particles
> which don't radiate unless they collide with something.
Neutrinos are now ruled out due to the constraints on their masses.
Chalky
> Chalky wrote:
> > I realise that CDM is only meant to interact gravitationally, but,
> > afaict, that is merely because it has only been postulated to 'balance
> > the (gravitational) books' . However, either in the form of MACHOS or
> > WIMPS, I can't see how it could fail to obey black body radiation
> > laws.
>
> > Would this create any problems astrophysically?
>
> Only if you consider asking how to make matter with no electromagnetic
> interaction interact electromagnetically a problem.
>
> > [[Mod. note -- I think the key defining characteristic of dark matter
> > is that it's "dark", i.e., it doesn't interact via the strong, weak,
> > or electromagnetic forces.
Not true. WMAP 5 year data analysis appears to indicate baryonic dark
matter which is at least an order of magnitude more prevalent than
luminous matter. (Here, baryonic does not mean comprising baryons, but
comprising baryons and electrons).
"Cold" dark matter (whatever that means) is less than an order of
magnitude more prevalent than "baryonic" dark matter.
> > Not interacting electromagnetically
> > implies that dark matter neither absorbs nor emits thermal
> > (black-body) radiation.
> > -- jt]]
On Dec 26, 10:39 pm, "jw...@BasicISP.net" <jw...@BasicISP.net> wrote:
> Also, "cold dark matter" can't, so far as I know, be distinguished
> from thinly-distributed, baseball-sized lumps of rock at or below
> radiative equilibrium with the CMB.
Do not rocks both radiate and absorb heat?
Chalky
undress to reply) wrote:
> In article
> <c4c2bad1-a35c-4911-a4ab-e7b986a61...@a6g2000yqm.googlegroups.com>,
>
> "jw...@BasicISP.net" <jw...@BasicISP.net> writes:
> > Also, "cold dark matter" can't, so far as I know, be distinguished
> > from thinly-distributed, baseball-sized lumps of rock at or below
> > radiative equilibrium with the CMB. �
>
> Observationally, no, at least not yet. �However, such "bricks" or
> whatever cannot be baryonic, due to constraints from nucleosynthesis.
Explain
> > We don't know what it
> > is -- it may be anything, including neutrinos or other particles
> > which don't radiate unless they collide with something.
>
> Neutrinos are now ruled out due to the constraints on their masses.
Agreed
Phillip Helbig---undress to reply
<1ba95178-a95a-4766...@n16g2000yqm.googlegroups.com>,
Chalky <chalk...@bleachboys.co.uk> writes:
> Not true. WMAP 5 year data analysis appears to indicate baryonic dark
> matter which is at least an order of magnitude more prevalent than
> luminous matter.
It has been known for a long time that there is much more baryonic
matter than luminous matter. There is even more non-baryonic dark
matter. Colloquially, "cold dark matter" usually means the much larger
non-baryonic part.
> (Here, baryonic does not mean comprising baryons, but
> comprising baryons and electrons).
Yes, but the mass of the electrons is negligible.
> > Also, "cold dark matter" can't, so far as I know, be distinguished
> > from thinly-distributed, baseball-sized lumps of rock at or below
> > radiative equilibrium with the CMB.
>
> Do not rocks both radiate and absorb heat?
Yes. However, the point is that we can't detect them observationally.
The next brick would be way too far away to detect it directly.
Basically, we see back until the radiating stuff becomes optically
thick. However, the optical depth of bricks is huge, because most lines
of sight don't hit one (because they are so massive, they are few and
far between).
eric gisse
> On Dec 25, 10:10 am, eric gisse <jowr.pi.nos...@gmail.com> wrote:
>> Chalky wrote:
>
>> > I realise that CDM is only meant to interact gravitationally, but,
>> > afaict, that is merely because it has only been postulated to 'balance
>> > the (gravitational) books' . However, either in the form of MACHOS or
>> > WIMPS, I can't see how it could fail to obey black body radiation
>> > laws.
>>
>> > Would this create any problems astrophysically?
>>
>> Only if you consider asking how to make matter with no electromagnetic
>> interaction interact electromagnetically a problem.
>>
>> > [[Mod. note -- I think the key defining characteristic of dark matter
>> > is that it's "dark", i.e., it doesn't interact via the strong, weak,
>> > or electromagnetic forces.
>
> Not true. WMAP 5 year data analysis appears to indicate baryonic dark
> matter
Which is odd, since I have read the 5 year data analysis regarding its'
implications for cosmology and it says nothing of the sort.
Could you show me where it says that in any of the published analysis
articles?
http://lambda.gsfc.nasa.gov/product/map/current/map_bibliography.cfm
> which is at least an order of magnitude more prevalent than
> luminous matter. (Here, baryonic does not mean comprising baryons, but
> comprising baryons and electrons).
You mis-spelled "nonbaryonic" and clearly meant to say "but neither
comprising baryons or electrons".
> "Cold" dark matter (whatever that means) is less than an order of
> magnitude more prevalent than "baryonic" dark matter.
Yes, "whatever that means". It could mean anything!
And again, you mis-spelled "nonbaryonic".
http://arxiv.org/abs/astro-ph/0608407
>
>> > Not interacting electromagnetically
>> > implies that dark matter neither absorbs nor emits thermal
>> > (black-body) radiation.
>> > -- jt]]
>
> On Dec 26, 10:39 pm, "jw...@BasicISP.net" <jw...@BasicISP.net> wrote:
>
>> Also, "cold dark matter" can't, so far as I know, be distinguished
>> from thinly-distributed, baseball-sized lumps of rock at or below
>> radiative equilibrium with the CMB.
>
> Do not rocks both radiate and absorb heat?
...and the source of these "rocks" would be what, exactly? And what would
they comprise, given the bullet cluster and similar observations?
Chalky
> Given that you can't get any darker than perfectly black, and
> perfectly black bodies radiate and absorb heat according to well known
> laws, isn't it likely that cold dark matter will radiate heat with a
> 2.73K black body spectrum?
With the benefit of hindsight I was clearly far too careless in my
original use of language here. By CDM I merely meant to mean the
matter which provides the lion's share of the mass of the universe. I
did not mean to mean such matter, necessarily constrained by the
entirety of the intellectual baggage that has subsequently been
ascribed to it, (presumably) based on the assumption that the
mathematical apparatus of standard cosmological theory serendipitously
becomes predictively accurate again, once all of its retrofit
adjustable free parameters (6 to date) have been optimally adjusted to
provide a best fit approximation to the (already accumulated)
observational evidence.
In other words, I am pitching this question in an intentionally
general manner, within the context of which it might be reasonable (as
well as more scientifically rigorous) to, at least, consider the
possibility that, if such a mathematical framework leads to the
conclusion that:
1) The lion's share of the dynamism of the universe (now) is
attributable to a mysterious "dark" (ie inadequately explained)
energy, and
2) The lion's share of the rest of that dynamism is attributable to a
mysterious "dark" (ie inadequately explained) form of matter,
then this could be suggestive of an associated (more powerfully
generalised) conclusion that that mathematical framework could itself
be inaccurate, and, by implication, that its own derivation could be
logically flawed.
> [[Mod. note -- I think the key defining characteristic of dark matter
> is that it's "dark", i.e., it doesn't interact via the strong, weak,
> or electromagnetic forces.
If so, now is hopefully the appropriate time to:
1) identify the classical constraints which lead to such apparently
bizarre conclusions (specifically in the context of CDM), and
2) discuss them.
On Dec 26, 10:39 pm, "jw...@BasicISP.net" <jw...@BasicISP.net> wrote:
> Also, "cold dark matter" can't, so far as I know, be distinguished
> from thinly-distributed, baseball-sized lumps of rock
Quite, which is why I mentioned MACHOS
> at or below
> radiative equilibrium with the CMB.
Hold on there cowboy! Anyone proposing lumps of rock colder than their
own global thermal bath, would need to explain how they lost heat
faster (from a big bang origin) than the thermal radiation surrounding
them, in direct violation of basic laws of thermodynamics (iiuc).
Phillip Helbig---undress to reply
<63abb1de-7939-44f2...@e37g2000yqn.googlegroups.com>,
Chalky <chalk...@bleachboys.co.uk> writes:
> > Observationally, no, at least not yet. However, such "bricks" or
> > whatever cannot be baryonic, due to constraints from nucleosynthesis.
>
> Explain
Just do an internet search for "big-bang nucleosynthesis". Even the
Wikipedia article is probably OK. Based on the observed ratios of the
light elements, one can calculate the baryonic density. It is way too
low to be the CDM.
Non-baryonic does not necessarily imply some sort of elementary
particle. There are other possibilities, for example primordial black
holes (formed BEFORE nucleosynthesis, so the baryon density doesn't
constrain them, since they didn't form from baryons). About 15 years
ago, Mike Hawkins suggested this, and claimed to have observationally
detected them, namely via microlensing effects in QSOs. It was a good
idea, but wrong; it made some testable predictions which were confirmed,
but was later disproved on other grounds. That is, the idea that
primordial black holes cause a large part of QSO variability is no
longer tenable. However, this doesn't rule out primordial black holes in
mass ranges which wouldn't show up via microlensing of QSOs, but it
would probably take an epicycle or two to avoid the mass range we could
detect.
For more information, see
@ARTICLE {EZackrissonNBergvallTMarquartPHelbig03a,
AUTHOR = "Erik Zackrisson and Nils Bergvall and
Thomas Marquart and Phillip Helbig",
TITLE = "Can microlensing explain the long-term
optical variability of quasars?",
JOURNAL = "Astronomy and Astrophysics",
YEAR = "2003",
VOLUME = "408",
NUMBER = "1",
PAGES = "17--25",
MONTH = sep
}
Chalky
> Chalky wrote:
> > On Dec 25, 10:10 am, eric gisse <jowr.pi.nos...@gmail.com> wrote:
> >> Chalky wrote:
> >> > [[Mod. note -- I think the key defining characteristic of dark matter
> >> > is that it's "dark", i.e., it doesn't interact via the strong, weak,
> >> > or electromagnetic forces.
>
> > Not true. WMAP 5 year data analysis appears to indicate baryonic dark
> > matter
>
> Which is odd, since I have read the 5 year data analysis regarding its'
> implications for cosmology and it says nothing of the sort.
>
> Could you show me where it says that in any of the published analysis
> articles?
Cosmological Interpretation. Abstract and Table 1. Figures for Omega_b
and Omega_b h squared. You do, of course, also need to know that the
density of luminous matter (stars) is much lower than this, but that
has been known since the 1930s.
See, for example
http://astro.berkeley.edu/~mwhite/darkmatter/rotcurve.html
> > which is at least an order of magnitude more prevalent than
> > luminous matter. (Here, baryonic does not mean comprising baryons, but
> > comprising baryons and electrons).
>
> You mis-spelled "nonbaryonic" and clearly meant to say "but neither
> comprising baryons or electrons".
No I did not.
> > "Cold" dark matter (whatever that means) is less than an order of
> > magnitude more prevalent than "baryonic" dark matter.
> > On Dec 26, 10:39 pm, "jw...@BasicISP.net" <jw...@BasicISP.net> wrote:
>
> >> Also, "cold dark matter" can't, so far as I know, be distinguished
> >> from thinly-distributed, baseball-sized lumps of rock at or below
> >> radiative equilibrium with the CMB.
>
> > Do not rocks both radiate and absorb heat?
>
> ...and the source of these "rocks" would be what, exactly? And what would
> they comprise, given the bullet cluster and similar observations?
I could also ask you the same question for every other candidate for
CDM
You could start at the beginning, by explaining your mechanism for
creating the big bang.
brad
> Could you show me where it says that in any of the published analysis
> articles?
Not WMAP. However, XXM-Newton results.
HTTP://www.sciencedaily.com/releases/2008/05/080506194033.htm
This isn't the DM normally being considered as the cause of galactic
rotational velocity ambiguities. Some of the confusion results from
missing matter predicted by constraints of nucleosynthesis; and this
article addresses that confusion.
Brad.
Richard D. Saam
baseball-sized lumps of rocks as dark matter
despite the their tantalizing long optical path characteristic
characteristic of their number density.
I think the main argument is that these rocks
would heat up over time (13.7 billion years)
from their creation at the Big Bang
and would be thermally detectable
if present in the amount to alter galactic rotation.
Maybe someone can quantify.
The Cosmic Background as CMBR 2.7 K is generally noted
as the temperature reference for the cold dark matter
but CMBR does not have enough energy mass/c^2 to sway the universe.
It is difficult to do, but Bose Einstein Condensates(BECs)
at ~1e-6 K have been made on earth
with 450 picokelvin (450E-12K) as the Guinness world BEC record holder MIT.
http://www.sciencemag.org/cgi/content/abstract/301/5639/1513
http://cua.mit.edu/ketterle_group/Introduction_to_BEC.htm
If it can be done on earth, these picokelvin temperature
probably are produced in astrophysical nature.
As an alternative 'dark matter' to small rocks and retaining the long
optical path characteristic,
hydrogen BEC's should be able to maintain their BEC character
over ~13 billion years since adiabatically produced at the Big Bang
because of their thermal equilibrium with a colder predominant
'Dark Energy' as indicated by the universe critical density
rho ~ H^2/G ~ 1E-29 g/cc at temperature < picokelvin
compared to
CMBR rho = Stefan_constant * 2.7^4 * 4/c^3 = 4.7E-34 g/cc
BEC hydrogen chunks would be very difficult to detect because they
respond only to a specific frequency.
Laboratory created MIT BECs did not respond to ambient light.
The 1S-2S characteristic BEC hydrogen transition
is at 243 nm (1.23E+15 hz)
compared to CMBR peak frequency:
2.82*Boltzmann*2.7K/(hbar*2*pi) = 4.76591E-05 Hz
This 243 nm 1S-2S transition would have to be initiated
before subsequent detectable Rydberg transitions.
This 243 nm (1.23E+15 hz) absorption is way out on the CMBR tale
and absorbing in a band width of ~1e6 hz.
Ref: Killian 1S-2S Spectrum of a Hydrogen Bose-Einstein Condensate
Physical Review A 61, 33611 (2000)
http://arxiv.org/abs/physics/9908002v3
Calculations indicate the einsteins absorbed
at this characteristic hydrogen BEC frequency
at 243 nm (band width of ~1e6 hz)
from CMBR would not substantially affect hydrogen BEC chunks over
universe life 13.7 billion years.
Generally the literature discusses primordial nucleosynthetic baryonic
production in terms of light element ratios (not absolute mass values)
which would not be altered by this dark matter hydrogen (light element)
BEC hypothesis nor would hydrogen BEC's be at odds with WMAP observed
Baryon Acoustic Oscillations (BAO)
http://arxiv.org/abs/0803.0547
Richard D. Saam
Chalky
undress to reply) wrote:
> In article
> <c4c2bad1-a35c-4911-a4ab-e7b986a61...@a6g2000yqm.googlegroups.com>,
>
> "jw...@BasicISP.net" <jw...@BasicISP.net> writes:
> > from thinly-distributed, baseball-sized lumps of rock at or below
> > radiative equilibrium with the CMB.
>
> whatever cannot be baryonic, due to constraints from nucleosynthesis.
What you say would probably be true, _if_ the modern 'stretched out'
BBN timescale is correct. However, if that timescale is correct, even
WMAP baryon densities would appear to be ruled out. Early BBN papers,
from well before the resurrection of the cosmological constant (the
mechanism for which has no rational physical explanation), indicated
shorter timescales, which would require more baryons to speed up the
process. I suggest the same is also likely to be true again for any
new theory proposing a more rational explanation for accelerating
expansion.
On Dec 28, 9:23�pm, hel...@astro.multiCLOTHESvax.de (Phillip Helbig---
undress to reply) wrote:
> In article
> <1ba95178-a95a-4766-b8e1-c587ad1a5...@n16g2000yqm.googlegroups.com>,
>
> Chalky <chalkys...@bleachboys.co.uk> writes:
> > Not true. WMAP 5 year data analysis appears to indicate baryonic dark
> > matter which is at least an order of magnitude more prevalent than
> > luminous matter.
>
> It has been known for a long time that there is much more baryonic
> matter than luminous matter.
Quite. Hopefully, you can help to convince Eric Geese of this.
>�There is even more non-baryonic dark
> matter. �Colloquially, "cold dark matter" usually means the much larger
> non-baryonic part.
Yes, however, I am beginning to suspect that, in the context of the
WMAP and BAO analyses at least, non-baryonic might only really mean
"not behaving like baryonic atoms, molecules, and stars"
> > (Here, baryonic does not mean comprising baryons, but
> > comprising baryons and electrons).
>
> Yes, but the mass of the electrons is negligible.
True, but their charges are extremely important for EM interactions
> > Do not rocks both radiate and absorb heat?
>
> Yes. �However, the point is that we can't detect them observationally.
> The next brick would be way too far away to detect it directly.
> Basically, we see back until the radiating stuff becomes optically
> thick. �However, the optical depth of bricks is huge, because most lines
> of sight don't hit one (because they are so massive, they are few and
> far between).
Yes, I think that was the whole point of proposing them.
However, unless anyone is going to be daft enough to propose a
primordial brick factory, I think a more plausible option would be a
range of such larger and denser conglomerations of matter.
Phillip Helbig---undress to reply
<62bc9344-2279-455f...@v25g2000yqk.googlegroups.com>,
Chalky <chalk...@bleachboys.co.uk> writes:
> In other words, I am pitching this question in an intentionally
> general manner, within the context of which it might be reasonable (as
> well as more scientifically rigorous) to, at least, consider the
> possibility that, if such a mathematical framework leads to the
> conclusion that:
>
> 1) The lion's share of the dynamism of the universe (now) is
> attributable to a mysterious "dark" (ie inadequately explained)
> energy, and
> 2) The lion's share of the rest of that dynamism is attributable to a
> mysterious "dark" (ie inadequately explained) form of matter,
>
> then this could be suggestive of an associated (more powerfully
> generalised) conclusion that that mathematical framework could itself
> be inaccurate, and, by implication, that its own derivation could be
> logically flawed.
This assumes that it is somehow unnatural that most matter not luminous.
Historically, obviously, we first detected luminous stuff (first
optically luminous, then in other wavebands), and maybe some folks
assumed that that is all there is. But that leap of faith is completely
unjustified. The "natural" assumption is that not everything radiates.
I would have been quite surprised had the determination of the
cosmological parameters indicated that we, with our primitive
astronomical tools, had already accounted for all the matter in the
universe.
Chalky
> On Dec 28, 4:23 pm, eric gisse <jowr.pi.nos...@gmail.com> wrote:
>
> > Could you show me where it says that in any of the published analysis
> > articles?
>
> Not WMAP. However, XXM-Newton results.
> HTTP://www.sciencedaily.com/releases/2008/05/080506194033.htm
>
> This isn't the DM normally being considered as the cause of galactic
> rotational velocity ambiguities.
Quite, it is intergalactic baryonic dark matter, which is obviously(?)
also predicted via the WMAP Omega_b figures.
I am not sure why the hottest of that dark matter was predicted (and
then observed) to be about a million times hotter than the CMB, but
that certainly does seem to be the case.
> Some of the confusion results from
> missing matter predicted by constraints of nucleosynthesis; and this
> article addresses that confusion.
If so, not in any obvious manner, afaict. I could only infer that
conclusion by considering the date of the original prediction (10
years ago, thus predating WMAP)
Incidentally, for the benefit of the unwary, I could only get the link
to work (in Google groups) by copying and pasting what you actually
typed, into the address bar of a browser. This would seem to be
because Google are currently trying to re-route hyperlinks back
through the Google server again for additional monitoring purposes
(and getting it wrong), so that all you get is a standard 404 "not
found" error, modified by a Google advert.
Chalky
> There are apparently some arguments against thinly-distributed,
> baseball-sized lumps of rocks as dark matter
> despite the their tantalizing long optical path characteristic
> characteristic of their number density.
> I think the main argument is that these rocks
> would heat up over time (13.7 billion years)
> from their creation at the Big Bang
> and would be thermally detectable
Mnhhh. Don't know about that! See http://www.sciencedaily.com/releases/2008/05/080506194033.htm,
and my recent associated response to Brad
> if present in the amount to alter galactic rotation.
> Maybe someone can quantify
.
Actually, we don't need _any_ CDM to explain galactic rotation
curves.
In fact, there is then sufficient (about equal) left over baryonic
dark matter to necessitate its additional spilling out into
intergalactic space.
Ditto for ref.
Best wishes
Chalky
undress to reply) wrote:
> In article
>
>
>
> Chalky <chalkys...@bleachboys.co.uk> writes:
> > In other words, I am pitching this question in an intentionally
> > general manner, within the context of which it might be reasonable (as
> > well as more scientifically rigorous) to, at least, consider the
> > possibility that, if such a mathematical framework leads to the
> > conclusion that:
>
> > 1) The lion's share of the dynamism of the universe (now) is
> > attributable to a mysterious "dark" (ie inadequately explained)
> > energy, and
> > 2) The lion's share of the rest of that dynamism is attributable to a
> > mysterious "dark" (ie inadequately explained) form of matter,
>
> > then this could be suggestive of an associated (more powerfully
> > generalised) conclusion that that mathematical framework could itself
> > be inaccurate, and, by implication, �that its own derivation could be
> > logically flawed.
>
> This assumes that it is somehow unnatural that most matter not luminous.
Not at all. Most matter in our immediate environment on Earth is not
luminous, and cannot even be seen unless illuminated.
That does not render it mysterious.
> Historically, obviously, we first detected luminous stuff (first
> optically luminous, then in other wavebands),
Actually, no. Our first interactions with our environment are not
optical, and probably begin before birth.
> and maybe some folks
> assumed that that is all there is. �
It would require an especially absent minded sort of professor to
forget about the planet he inhabits as well as his own body :-)
> But that leap of faith is completely
> unjustified. �The "natural" assumption is that not everything radiates.
> I would have been quite surprised had the determination of the
> cosmological parameters indicated that we, with our primitive
> astronomical tools, had already accounted for all the matter in the
> universe.
Agreed
Our ability to reason provides us with the potential to achieve a more
powerful and predictively accurate understanding of nature, and it is
up to us whether we use it or not.
brad
undress to reply) wrote:
> However, this doesn't rule out primordial black holes in
> mass ranges which wouldn't show up via microlensing of QSOs, but it
> would probably take an epicycle or two to avoid the mass range we could
> detect.
Here's an interesting article concerning primordial black holes.
HTTP://www.sciencedaily.com/releases/2009/11/091130112413.htm
Brad
Phillip Helbig---undress to reply
(Phillip Helbig---undress to reply) writes:
> > > Also, "cold dark matter" can't, so far as I know, be distinguished
> > > from thinly-distributed, baseball-sized lumps of rock at or below
> > > radiative equilibrium with the CMB.
> >
> > Do not rocks both radiate and absorb heat?
>
> Yes. However, the point is that we can't detect them observationally.
> The next brick would be way too far away to detect it directly.
> Basically, we see back until the radiating stuff becomes optically
> thick. However, the optical depth of bricks is huge, because most lines
> of sight don't hit one (because they are so massive, they are few and
> far between).
That should be "tiny" instead of "huge". The mean free path of photons
passing through such an assemblage of bricks is huge, which corresponds
to a tiny optical depth.
Phillip Helbig---undress to reply
<aefe3327-176e-4780...@d21g2000yqn.googlegroups.com>,
Chalky <chalk...@bleachboys.co.uk> writes:
> > This assumes that it is somehow unnatural that most matter not luminous.
>
> Not at all. Most matter in our immediate environment on Earth is not
> luminous, and cannot even be seen unless illuminated.
> That does not render it mysterious.
I was talking about the universe as a whole. Most of what we see is
luminous (obviously); planets have negligible mass in comparison.
> > Historically, obviously, we first detected luminous stuff (first
> > optically luminous, then in other wavebands),
>
> Actually, no. Our first interactions with our environment are not
> optical, and probably begin before birth.
Again, I was talking about historical astronomical observations. Sorry
for not being explicit. :-|
> It would require an especially absent minded sort of professor to
> forget about the planet he inhabits as well as his own body :-)
Again, negligible mass compared to the Sun.
Chalky
undress to reply) wrote:
> In article
You are reasoning here within the context of the paradigm shift from
the Ptolemaic system to the Copernican system.
However, this paradigm shift is largely negated by the general
principle of relativity.
Just as our local environment is dominated by non luminous matter, so
is the universe, at least gravitationally, as we both know.
eric gisse
> On Dec 28, 9:23 pm, eric gisse <jowr.pi.nos...@gmail.com> wrote:
>> Chalky wrote:
>> > On Dec 25, 10:10 am, eric gisse <jowr.pi.nos...@gmail.com> wrote:
>> >> Chalky wrote:
>
>> >> > [[Mod. note -- I think the key defining characteristic of dark
>> >> > [[matter
>> >> > is that it's "dark", i.e., it doesn't interact via the strong, weak,
>> >> > or electromagnetic forces.
>>
>> > Not true. WMAP 5 year data analysis appears to indicate baryonic dark
>> > matter
>>
>> Which is odd, since I have read the 5 year data analysis regarding its'
>> implications for cosmology and it says nothing of the sort.
>>
>> Could you show me where it says that in any of the published analysis
>> articles?
>
> Cosmological Interpretation. Abstract and Table 1. Figures for Omega_b
> and Omega_b h squared. You do, of course, also need to know that the
> density of luminous matter (stars) is much lower than this, but that
> has been known since the 1930s.
> See, for example
> http://astro.berkeley.edu/~mwhite/darkmatter/rotcurve.html
Curiously enough this does not support your claim that dark matter is
baryonic in nature. The WMAP team's usage of the Lamba-CDM model
specifically assumes nonbaryonic dark matter.
>
>> > which is at least an order of magnitude more prevalent than
>> > luminous matter. (Here, baryonic does not mean comprising baryons, but
>> > comprising baryons and electrons).
>>
>> You mis-spelled "nonbaryonic" and clearly meant to say "but neither
>> comprising baryons or electrons".
>
> No I did not.
Well then you are wrong. My mistake.
>
>> > "Cold" dark matter (whatever that means) is less than an order of
>> > magnitude more prevalent than "baryonic" dark matter.
>
Right about here I posted an arXiv link by Clowe, et. al, regarding the
bullet cluster. A read of that paper would make it understood exactly why
dark matter is assumed to be nonbaryonic.
Perhaps reading isn't your strong suite? Maybe that's why the link isn't
there anymore?
Let's look at a picture instead. Everyone likes pictures.
http://apod.nasa.gov/apod/ap060824.html
>> > On Dec 26, 10:39 pm, "jw...@BasicISP.net" <jw...@BasicISP.net> wrote:
>>
>> >> Also, "cold dark matter" can't, so far as I know, be distinguished
>> >> from thinly-distributed, baseball-sized lumps of rock at or below
>> >> radiative equilibrium with the CMB.
>>
>> > Do not rocks both radiate and absorb heat?
>>
>> ...and the source of these "rocks" would be what, exactly? And what
>> would they comprise, given the bullet cluster and similar observations?
>
> I could also ask you the same question for every other candidate for
> CDM
> You could start at the beginning, by explaining your mechanism for
> creating the big bang.
You could have said "I'm just making stuff up" with a lot fewer words in a
far less intellectually insulting manner.
Just so I'm explicit, you are unable to explain where your magical rocks are
coming from. Further examination of the magical rock theory indicates a
profound lack of understanding of basic astrophysics, as the matter that
comprises rocks is exclusively made of material that can only be produced by
fusion in a star. How you imagine "rock" to outmass all the visible matter
in the universe without condensing, glowing, or otherwise interacting like
the rest of the rocks we know about is an interesting conundrum.
Chalky
> Curiously enough this does not support your claim that dark matter is
> baryonic in nature.
Firstly, I am not claiming that. As I touched on in a prior response
to Phillip Helbig, all I am trying to do is explore possibilities
which _might_ pertain if the standard model is not as accurate as you
think it is. (This group is, after all, called sci.physics.research,
not sci.physics.pedantry)
Secondly, part of the confusion here is that some sources define dark
matter as everything other than optically luminous matter (such as in
http://astro.berkeley.edu/~mwhite/darkmatter/rotcurve.html) and others
define it in the narrower sense you subscribe to. This does not mean
one is right and one is wrong, it just means we are talking different
languages. If you DO want to be pedantic, then, in English, dark means
emitting little (or no) light, hence difficult (or impossible) to see
(consistent with above Berkeley usage), whereas you, and your
subscription group are using it to only mean impossible to see (and,
thus, perfectly transparent). That is an abuse of English, hence
inherently conducive to confusion.
> The WMAP team's usage of the Lamba-CDM model
> specifically assumes nonbaryonic dark matter.
Obviously.
It also assumes baryonic matter which is not visible in the optical
range. i.e. dark matter in the above Berkeley sense
> Right about here I posted an arXiv link by Clowe, et. al, regarding the
> bullet cluster. A read of that paper would make it understood exactly why
> dark matter is assumed to be nonbaryonic.
Not in the abstract or introduction, and I can't be bothered to read
further, as this merely seems to be a matter of pedantry, not science,
for you.
> Let's look at a picture instead. Everyone likes pictures.
Agreed
> http://apod.nasa.gov/apod/ap060824.html
Perhaps you have not noticed. There are two distributions not visible
in the optical range. The first (coloured blue) is obviously baryonic
(and hot) because it is described as hot x ray emitting gas. If you
have not checked yet, such x ray emissions are indicative of heavy
metals such as carbon and oxygen which can only be produced in stars.
The second, coloured blue, has roughly the same extension, and is
merely inferred from gravitational lensing. I can see absolutely
nothing in that picture to rule out the possibility of larger chunks
of supernova produced metals as the cause of that.
> >> ...and the source of these "rocks" would be what, exactly? �And what
> >> would they comprise, given the bullet cluster and similar observations?
>
> > I could also ask you the same question for every other candidate for
> > CDM
>
> You could have said "I'm just making stuff up" with a lot fewer words in a
> far less intellectually insulting manner.
As could you. I have answered your question. It is now time for you to
answer mine
> Just so I'm explicit, you are unable to explain where your magical rocks are
> coming from.
I think I just did
> Further examination of the magical rock theory indicates a
> profound lack of understanding of basic astrophysics, as the matter that
> comprises rocks is exclusively made of material that can only be produced by
> fusion in a star.
Well, duh!
Given the impunity of your insults, I think I should (and so will) add
the following comment:
Your criticism indicates a profound lack of understanding of the
relativistic nature of time, when the consequences of the relativistic
axioms are examined outside of the context of the standard model.
Phillip Helbig---undress to reply
<jowr.pi...@gmail.com> writes:
> Just so I'm explicit, you are unable to explain where your magical rocks are
> coming from. Further examination of the magical rock theory indicates a
> profound lack of understanding of basic astrophysics, as the matter that
> comprises rocks is exclusively made of material that can only be produced by
> fusion in a star. How you imagine "rock" to outmass all the visible matter
> in the universe without condensing, glowing, or otherwise interacting like
> the rest of the rocks we know about is an interesting conundrum.
You're missing a point which I didn't think needs making: the discussion
of rocks and bricks as a candidate for the unidentified dark matter is
not meant literally, since they would be baryonic. Rather, it
illustrates what is possible in terms of distribution while still being
compatible with observations. Non-baryonic "bricks" are ad-hoc of
course and no-one suggests them as a serious candidate; they are more of
a devil's advocate to illustrate what we could detect with current
observational techniques.
Richard D. Saam
Qualitatively you are right with the terms "tiny" and "huge"
but what are the dimensional calculation
for an actual astrophysical object
such as the Bullet Cluster
For instance, lensing observations on Bullet Cluster E0657-56:
arXiv:astro-ph/0608408 v1 page 9 allow estimation of 'dark matter' density
Bullet Cluster E0657-56 length 250 kpc (7.7E+23 cm)
Bullet Cluster E0657-56 mass 2.80E+14 solar mass (5.6E+47 g)
then
Bullet Cluster E0657-56 density 1.2E-24 g/cm3
(This is about the same density as our galaxy.)
But this indicates nothing of how the mass is distributed
- continuous or chunks.
So what is the calculated optical depth of the Bullet Cluster using mean
free path concept?
http://en.wikipedia.org/wiki/Mean_free_path
d = particle size (assume spherical 10 cm balls)
rho1 = particle & space density = 1.2E-24 g/cm^3
rho2 = particle density (assume 1 g/cm^3)
n = # of particles per volume = (6/pi)*(rho1/rho2)*1/d^3
= (6/pi)*(1.2E-24/1)*1/10^3
= 2.3E-27 /cm^3
l = photon mean free path = 1/(sqrt(2)*n*d^2)
= 1/(sqrt(2)*2.3E-27*10^2)
= 3.0E24 cm
x = observational length 7.7E+23 cm
optical depth = x/l = 7.7E+23/3.0E24 = .26
Transmittance = I/Io = exp(-x/l) = exp(-.26)
= .77
Observed transmittance appears to be greater than this.
The above calculations for d = 100 cm balls
achieves a Bullet Cluster mean free path of 3E25 cm
and Bullet Cluster Transmittance of exp(-.026) = .97
which is more reasonable
(one can see through the Bullet Cluster while it maintains its
gravitational lensing property).
As an aside, the average distance between these 100 cm balls would be
9/(pi*n)^(1/3) = 9/(pi*2.3E-30)^(1/3) = 4.6E10 cm
If you were on one, it would be difficult to see the next.
This analysis would explain a non observable brick baryonic contribution
to observable galactic rotation.
This analysis indicates nothing about the brick chemical nature.
As others have pointed out,
heavy element bricks cannot originate
in the Big Bang nucleosynthetic event.
What if they were light element (hydrogen -) bricks in the ratios
believed to produced by nucleosynthesis.
These bricks would have to extremely cold (pico kelvin)
(much colder than CMBR 2.7 K)
adiabatically produced at the Big Bang
and would have had to survive over 13.7 billions years
since the Big Bang.
Light Element Bose Einstein Condensate bricks fit these criteria
and could be considered 'dark matter'.
Richard D. Saam
Phillip Helbig---undress to reply
<baefe111-ee51-410e...@e27g2000yqd.googlegroups.com>,
Chalky <chalk...@bleachboys.co.uk> writes:
> > Again, negligible mass compared to the Sun.
>
> You are reasoning here within the context of the paradigm shift from
> the Ptolemaic system to the Copernican system.
The mass of the planets compared to that of the Sun is very small,
whether one subscribes to the Ptolemaic or Copernican or Tychonian
system.
> However, this paradigm shift is largely negated by the general
> principle of relativity.
In some sense, perhaps, but in a practical sense the center of mass of
the Solar System is closer to the centre of the Sun than to the centre
of the Earth, so it does make more sense to say that the Earth goes
around the Sun, rather than vice versa.
> Just as our local environment is dominated by non luminous matter, so
> is the universe, at least gravitationally, as we both know.
Yes, but the dominant matter in the Universe is very different from that
of the Earth. (As I'm writing this, I'm dominated by my luminous
computer screen. :-) )
jw...@basicisp.net
>
> > at or below
> > radiative equilibrium with the CMB.
>
> Hold on there cowboy! Anyone proposing lumps of rock colder than their
> own global thermal bath, would need to explain how they lost heat
> faster (from a big bang origin) than the thermal radiation surrounding
> them, in direct violation of basic laws of thermodynamics (iiuc).
You may be confused by your metaphor, "thermal bath", which
applies to laboratory solids immersed in a liquid.
An object can be at radiative equilibrium only when the HEAT
FLOW, not temperature, is in balance. If heat flow from the CMB
into a body is less than radiation from that body, then the CMB
will not be able to keep it in equilibrium. Why not ask why
"cold, dark matter" is not in equilibrium at 5,000 C, the
approximate average surface temperature of stars? Surely,
"cold, dark matter" could be described as immersed in a
"heat bath" of starlight?
I don't know whether "cold, dark matter" is in equilibrium with
the CMB -- it might be, but, because the CMB is believed to
originate from an enormous space-time interval, perhaps it
is not? None of the CMB is radiated locally, I think.
Can you clarify why you described the CMB as a "heat bath"?
[[Mod. note -- Saying that some object is in "radiative equilibrium
with the CMB" is usually a shorthand for saying that it's *locally*
in equilibrium with the CMB photon-bath, i.e., that it's asorbing
the same amount of energy-per-unit-time from the CMB as it's emitting
in thermal radiation. We neglect any (hypothetical) energy transfer
from the local object back to the CMB-last-scattering-surface matter,
since that would take a very *very* long time...
-- jt]]
Chalky
> The above calculations for d = 100 cm balls
> achieves a Bullet Cluster mean free path of 3E25 cm
> and Bullet Cluster Transmittance of exp(-.026) = .97
> which is more reasonable
> (one can see through the Bullet Cluster while it maintains its
> gravitational lensing property).
Thanks for doing the maths for us, which I am just accepting, without
repeating your calculation.
However, it seems to me that these balls could be made even bigger
without causing observational problems.
> As an aside, the average distance between these 100 cm balls would be
> 9/(pi*n)^(1/3) = 9/(pi*2.3E-30)^(1/3) = 4.6E10 cm
> If you were on one, it would be difficult to see the next.
>
> This analysis would explain a non observable brick baryonic contribution
> to observable galactic rotation.
And, more importantly, much of the missing mass of galactic clusters.
> This analysis indicates nothing about the brick chemical nature.
> As others have pointed out,
> heavy element bricks cannot originate
> in the Big Bang nucleosynthetic event.
> What if they were light element (hydrogen -) bricks in the ratios
> believed to produced by nucleosynthesis.
Yes, precisely. However, the important point here is that if we boost
the number of baryons, we need to reduce the BBN timespan
accordingly.
I have just submitted a new post on precisely that subject.
> These bricks would have to extremely cold (pico kelvin)
> (much colder than CMBR 2.7 K)
I don't see why they would necessarily need to be that cold.
Despite the absolute certainty of Eric Gisse, NASA still list brown
dwarfs as plausible candidates at
http://map.gsfc.nasa.gov/universe/uni_matter.html
Similarly, black holes could radiate (If the mechanism for Hawking
radiation is valid), and the temperature of that radiation would
depend on their typical size (now)
Interestingly, such black holes could potentially be pre BBN, post
BBN, or both (depending on the predicted BBN timespan of one's
proposed theoretical framework)
Chalky
undress to reply) wrote:
> In article
>
> Chalky <chalkys...@bleachboys.co.uk> writes:
> > > Again, negligible mass compared to the Sun.
>
> > You are reasoning here within the context of the paradigm shift from
> > the Ptolemaic system to the Copernican system.
>
> The mass of the planets compared to that of the Sun is very small,
> whether one subscribes to the Ptolemaic or Copernican or Tychonian
> system.
However, under the general principle (in its purest Einsteinian
expression) that is not particularly relevant:
I repeat "All bodies of reference are essentially equivalent for
formulating general laws of nature, irrespective of their state of
motion".
Note that, despite Einstein's effective qualification "provided they
employ Gaussian coordinates", that does not definitively extend to
what you seem to be adding, which is:
"With the proviso that their statistical weight is directly
proportional to their mass"
> > However, this paradigm shift is largely negated by the general
> > principle of relativity.
>
> In some sense, perhaps, but in a practical sense the center of mass of
> the Solar System is closer to the centre of the Sun than to the centre
> of the Earth, so it does make more sense to say that the Earth goes
> around the Sun, rather than vice versa.
>
> > Just as our local environment is dominated by non luminous matter, so
> > is the universe, at least gravitationally, as we both know.
>
> Yes, but the dominant matter in the Universe is very different from that
> of the Earth.
Not in the sense it is not luminous
>(As I'm writing this, I'm dominated by my luminous
> computer screen. :-) )
Matbe you are, but I am not, perhaps because I am inherently a bit
more pregeometric than you. Although my computer screen is on, I am
actually dominated by the pressure on my elbows induced by my writing
desk, and the pressure on my bladder which tells me I need a pee. So,
'bye for now, we will discuss this again later.
Chalky
> ...
>
>
>
> > > at or below
> > > radiative equilibrium with the CMB.
>
> > Hold on there cowboy! Anyone proposing lumps of rock colder than their
> > own global thermal bath, would need to explain how they lost heat
> > faster (from a big bang origin) than the thermal radiation surrounding
> > them, in direct violation of basic laws of thermodynamics (iiuc).
>
> You may be confused by your metaphor, "thermal bath", which
> applies to laboratory solids immersed in a liquid.
I think it applies more generally
> An object can be at radiative equilibrium only when the HEAT
> FLOW, not temperature, is in balance. If heat flow from the CMB
> into a body is less than radiation from that body, then the CMB
> will not be able to keep it in equilibrium. Why not ask why
> "cold, dark matter" is not in equilibrium at 5,000 C, the
> approximate average surface temperature of stars? Surely,
> "cold, dark matter" could be described as immersed in a
> "heat bath" of starlight?
Interesting point. In this respect, it is worth noting that the
"temperature" of intergalactic gas is actually far in excess of the
temperature of starlight
> I don't know whether "cold, dark matter" is in equilibrium with
> the CMB -- it might be, but, because the CMB is believed to
> originate from an enormous space-time interval, perhaps it
> is not? None of the CMB is radiated locally, I think.
>
> Can you clarify why you described the CMB as a "heat bath"?
Because I am "brainstorming" here, in addition to the more salubrious
reason given below, by the moderator.
> [[Mod. note -- Saying that some object is in "radiative equilibrium
> with the CMB" is usually a shorthand for saying that it's *locally*
> in equilibrium with the CMB photon-bath, i.e., that it's asorbing
> the same amount of energy-per-unit-time from the CMB as it's emitting
> in thermal radiation. We neglect any (hypothetical) energy transfer
> from the local object back to the CMB-last-scattering-surface matter,
> since that would take a very *very* long time...
> -- jt]]
Perhaps infinite.
Phillip Helbig---undress to reply
<75bd8c2f-a680-4002...@c3g2000yqd.googlegroups.com>,
Chalky <chalk...@bleachboys.co.uk> writes:
> > > > radiative equilibrium with the CMB.
> >
> > > Hold on there cowboy! Anyone proposing lumps of rock colder than their
> > > own global thermal bath, would need to explain how they lost heat
> > > faster (from a big bang origin) than the thermal radiation surrounding
> > > them, in direct violation of basic laws of thermodynamics (iiuc).
> >
> > You may be confused by your metaphor, "thermal bath", which
> > applies to laboratory solids immersed in a liquid.
>
> I think it applies more generally
>
> Interesting point. In this respect, it is worth noting that the
> "temperature" of intergalactic gas is actually far in excess of the
> temperature of starlight
>
> > I don't know whether "cold, dark matter" is in equilibrium with
> > the CMB -- it might be, but, because the CMB is believed to
> > originate from an enormous space-time interval, perhaps it
> > is not? None of the CMB is radiated locally, I think.
> >
> > Can you clarify why you described the CMB as a "heat bath"?
>
> Because I am "brainstorming" here, in addition to the more salubrious
> reason given below, by the moderator.
>
> > [[Mod. note -- Saying that some object is in "radiative equilibrium
> > with the CMB" is usually a shorthand for saying that it's *locally*
> > in equilibrium with the CMB photon-bath, i.e., that it's asorbing
> > the same amount of energy-per-unit-time from the CMB as it's emitting
> > in thermal radiation. We neglect any (hypothetical) energy transfer
> > from the local object back to the CMB-last-scattering-surface matter,
> > since that would take a very *very* long time...
> > -- jt]]
Relevant to this is the so-called Olbers Paradox: why is the sky dark at
night? The universe could be infinite (current wisdom suggests that it
is just at the dividing line between infinite and finite; in any case,
quite big), so any line of sight should hit the surface of a star. Why
isn't everything at the temperature of a stellar atmosphere? The answer
(note that, historically, there have been many incorrect suggestions for
the solution; see the oft-cited book by Edward Harrison for a detailed
discussion) is that the universe is too young; light from distant stars
hasn't had time to reach us (even disregarding the fact that, due to the
expansion of the universe, it might NEVER reach us; the interesting
point is that this resolution of the paradox works even in a static
infinite universe, as long as it isn't too old).
Richard D. Saam
> Thanks for doing the maths for us, which I am just accepting, without
> repeating your calculation.
>
> However, it seems to me that these balls could be made even bigger
> without causing observational problems.
Yes
bert
> [[Mod. note -- I think the key defining characteristic of dark matter
> is that it's "dark", i.e., it doesn't interact via the strong, weak,
> or electromagnetic forces. Not interacting electromagnetically
> implies that dark matter neither absorbs nor emits thermal
> (black-body) radiation.
BH absorbs space heat. Treb
bert
[[Mod. note -- 34 excessively-quoted lines snipped. -- jt]]
> You are reasoning here within the context of the paradigm shift from
> the Ptolemaic system to the Copernican system.
> However, this paradigm shift is largely negated by the general
> principle of relativity.
> Just as our local environment is dominated by non luminous matter, so
> is the universe, at least gravitationally, as we both know.
Chalky BH radiates no heat,so its colder than the space its in. Fact
is I have a theory that black hole all alone in space get more dense
from space energy TreBert