Can a Particle with Repulsive Properties Explain Dark Matter and Dark Energy?

In summary, the conversation discusses the possibility of a particle that could explain both dark matter and dark energy. However, it is unlikely that such a particle exists, and more exotic solutions are being considered. The most reasonable explanation for dark matter is a WIMP, but this is still an unproven theory.
  • #1
E45
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If it existed a particle that had such properties that it both pushed away other particles of the same kind and it pushed away ordinary matter ,could this then explain dark matter and dark energy ? If the big voids of the universe was filled with such a particle, the net force of the particles in the universe would be outwards ,so the expansion would accelerate.

If particles of this type surrounded a galaxy,they would push the edges of that galaxy inwards, so that the stars far from the center of that galaxy would increase their speed ,and it has been observed that the stars in a galaxy have a greater velocity than expected.

In a cluster of galaxy this type of particle could push the galaxies together, allowing them to have a greater velocity than expected without escaping from the cluster,and this greater than expected speed has been observed.

This particle could also explain the big voids in the universe,it would be a natural consequence of the particles properties.
 
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  • #2
Dark matter is not repulsive, it is attractive through gravity both with itself and to normal matter. The speed of stars orbiting a galaxy is only one phenomenon believed to be caused by dark matter. There is also things like Gravitational Lensing that must be explained.

Also I don't believe this would fit the models for the expansion of the universe. For example, in your case the repulsive force would decrease over time at the same rate as gravitation does due to the average density of the universe decreasing. Instead we see that as the density decreases and gravity becomes weaker, the repulsive force does not. Hence we see increasing acceleration.
 
  • #3
E45 said:
If it existed a particle that had such properties that it both pushed away other particles of the same kind and it pushed away ordinary matter ,could this then explain dark matter and dark energy ? If the big voids of the universe was filled with such a particle, the net force of the particles in the universe would be outwards ,so the expansion would accelerate.
Unfortunately it isn't that easy. First, as Drakkith noted, dark matter produces pretty large gravitational potential wells: it attracts matter quite strongly. You also won't get dark matter that clumps if it doesn't attract itself, and the dark matter we observe is pretty clumpy.

As for dark energy, the problem there is that matter that pushes itself away has the wrong sign to pressure. Matter that pushes itself away would experience positive pressure. Dark energy has negative pressure.
 
  • #4
E45 said:
If it existed a particle that had such properties that it both pushed away other particles of the same kind and it pushed away ordinary matter ,could this then explain dark matter and dark energy ? If the big voids of the universe was filled with such a particle, the net force of the particles in the universe would be outwards ,so the expansion would accelerate.

If particles of this type surrounded a galaxy,they would push the edges of that galaxy inwards, so that the stars far from the center of that galaxy would increase their speed ,and it has been observed that the stars in a galaxy have a greater velocity than expected.

In a cluster of galaxy this type of particle could push the galaxies together, allowing them to have a greater velocity than expected without escaping from the cluster,and this greater than expected speed has been observed.

This particle could also explain the big voids in the universe,it would be a natural consequence of the particles properties.

Does not exists any particle that can explain the properties of dark matter or dark energy alone, less still both at once.
 
  • #5
juanrga said:
Does not exists any particle that can explain the properties of dark matter or dark energy alone, less still both at once.
Uh, what? Dark matter is easily explained by a WIMP, of which many theoretical ideas have been proposed. Dark energy is most likely to be the cosmological constant, which is not a particle. But there are many scalar fields that could also do the same thing.
 
  • #6
Chalnoth said:
Uh, what? Dark matter is easily explained by a WIMP, of which many theoretical ideas have been proposed. Dark energy is most likely to be the cosmological constant, which is not a particle. But there are many scalar fields that could also do the same thing.

I did mean a real particle. Of course, you can imagine hypothetical particles with all properties that you want.
 
  • #7
juanrga said:
I did mean a real particle. Of course, you can imagine hypothetical particles with all properties that you want.
(Leaving dark energy out of this, for the moment...)
1. No particle in the standard model explains dark matter. So if it's a particle, it has to be a new particle we haven't seen in the lab before. The most reasonable numbers for a particle that would explain our cosmological observations predict that it would be extremely hard to detect anyway, so this isn't a surprise.
2. Non-particle solutions to the dark matter problem are far more exotic than particle solutions.

So the most reasonable conclusion is that it's probably a WIMP.
 
  • #8
Chalnoth said:
(Leaving dark energy out of this, for the moment...)
1. No particle in the standard model explains dark matter.

That was my point.

Chalnoth said:
So if it's a particle, it has to be a new particle we haven't seen in the lab before. The most reasonable numbers for a particle that would explain our cosmological observations predict that it would be extremely hard to detect anyway, so this isn't a surprise.

A lot of modern theoretical 'physics' is so safe because focuses on the experimental range that goes from the «extremely hard to detect» up to the limit of the undetectable :rolleyes:

Chalnoth said:
2. Non-particle solutions to the dark matter problem are far more exotic than particle solutions.

So the most reasonable conclusion is that it's probably a WIMP.

A more reasonable conclusion is that dark matter is a fictitious distribution of mass and thus WIMPs do not exist, what means that people's money would not be wasted in their search.
 
  • #9
juanrga said:
A more reasonable conclusion is that dark matter is a fictitious distribution of mass and thus WIMPs do not exist, what means that people's money would not be wasted in their search.

So which of the following is it that you believe, or is it both
(1) physicists are so stupid that they are incorrect in their conclusions regarding the existence of dark matter AND the likelihood that it is WIMPS
(2) physicists are so corrupt that they pretend dark matter exists so they can get research money to pretend to study it.

Oh ... there is a third possibility:

(3) you don't know what you are talking about.
 
  • #10
juanrga said:
A more reasonable conclusion is that dark matter is a fictitious distribution of mass and thus WIMPs do not exist, what means that people's money would not be wasted in their search.
To that I say look at the evidence. It is quite conclusive.
 
  • #11
Chalnoth said:
To that I say look at the evidence. It is quite conclusive.

Chanlnoth, you are SO much more polite than I am. I should follow your example, and I DO try most of the time, but sometimes I find that, in the words of my favorite poet, e e cummings, "there is some s***, up with which I will not put".
 
  • #12
phinds said:
Chanlnoth, you are SO much more polite than I am. I should follow your example, and I DO try most of the time, but sometimes I find that, in the words of my favorite poet, e e cummings, "there is some s***, up with which I will not put".
Don't let this one example fool you ;)
 
  • #13
Chalnoth said:
To that I say look at the evidence. It is quite conclusive.

Effectively the several premature claims of detection have gone (although are recorded by historians of science :uhh: ) and stuff as WIMPs continue without being real particles...
 
  • #14
juanrga said:
Effectively the several premature claims of detection have gone (although are recorded by historians of science :uhh: ) and stuff as WIMPs continue without being real particles...
What's your point? The astrophysical and cosmological observations are firm and verified.
 
  • #15
juanrga said:
Effectively the several premature claims of detection have gone (although are recorded by historians of science :uhh: ) and stuff as WIMPs continue without being real particles...

Chalnoth said:
What's your point? The astrophysical and cosmological observations are firm and verified.

And another premature claim of observation of dark matter has gone when latest Fermi studies have found no trace of dark matter (once again)

http://physicsworld.com/cws/article/news/48079

But not true believer in dark matter would worry because all the tests of direct observation have failed... because the 'observations' are so «firm and verified» as the 'observations' of caloric were :rofl:
 
  • #16
juanrga said:
And another premature claim of observation of dark matter has gone when latest Fermi studies have found no trace of dark matter (once again)

http://physicsworld.com/cws/article/news/48079

But not true believer in dark matter would worry because all the tests of direct observation have failed... because the 'observations' are so «firm and verified» as the 'observations' of caloric were :rofl:
I see you are completely ignoring the cosmological evidence such as WMAP or gravitational lensing studies.
 
  • #17
Chalnoth said:
I see you are completely ignoring the cosmological evidence such as WMAP or gravitational lensing studies.

Evidently neither WMAP nor gravitational lensing are direct observations of dark matter {*}. That is the reason which experiments as that reported by Physics World (link given before) have been performed and all they have failed. Not a surprise that each experiment looking for dark matter, WIMPS, and all that stuff has failed, since dark matter is so fictitious as caloric was centuries ago. And recall that many clever guys said to the ignorants that caloric had been observed in hundred of observations and experiments :rofl:

{*} In fact, discrepancies between observation and theory are, a posteriori, interpreted as resulting from some hypothetical invisible matter.

To say more, since you seem ignorant of the history of the scientific topic that your pretend to know. The first prediction of what WMAP would detect was done by a non-DM theory. Whereas the predictions done by DM-theory (lambda 1999 model) miserably failed and only after the observations were obtained that the DM model was modified (pure curve fitting) to adapt it to the WMAP observations a posteriori.

However, the non-DM model predicted exactly the first and second peaks, i.e., before the observations.
 
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  • #18
juanrga said:
Evidently neither WMAP nor gravitational lensing are direct observations of dark matter {*}. That is the reason which experiments as that reported by Physics World (link given before) have been performed and all they have failed. Not a surprise that each experiment looking for dark matter, WIMPS, and all that stuff has failed, since dark matter is so fictitious as caloric was centuries ago. And recall that many clever guys said to the ignorants that caloric had been observed in hundred of observations and experiments :rofl:
Then what, pray tell, is the explanation?

juanrga said:
{*} In fact, discrepancies between observation and theory are, a posteriori, interpreted as resulting from some hypothetical invisible matter.

To say more, since you seem ignorant of the history of the scientific topic that your pretend to know. The first prediction of what WMAP would detect was done by a non-DM theory. Whereas the predictions done by DM-theory (lambda 1999 model) miserably failed and only after the observations were obtained that the DM model was modified (pure curve fitting) to adapt it to the WMAP observations a posteriori.

However, the non-DM model predicted exactly the first and second peaks, i.e., before the observations.
This is pure, unadulterated fantasy. The dark matter model used in nearly all WMAP data analysis is the simplest possible: zero-temperature dark matter. This model fits the data exceedingly well. There is no curve fitting done with respect to dark matter in analyzing the WMAP data, except in terms of estimating the values of the various parameters. The simplest model for WMAP uses the following parameters:

1. Dark matter density.
2. Normal matter density.
3. Hubble expansion rate.
4. Scalar spectral index (an inflation parameter).
5. Optical depth to the CMB (basically, how transparent the universe is between us and the CMB).
6. Amplitude of fluctuations.

Each one of these parameters is physically-motivated. There is no "curve fitting" going on. Each one of the parameters which can be estimated independently with other experiments shows the same result for those parameters. The various extensions of this minimalist model, such as allowing spatial curvature to vary, or allowing the scalar spectral index to change with scale, so far show no evidence of deviation from this simplest description.
 
  • #19
Chalnoth said:
juanrga said:
{*} In fact, discrepancies between observation and theory are, a posteriori, interpreted as resulting from some hypothetical invisible matter.

To say more, since you seem ignorant of the history of the scientific topic that your pretend to know. The first prediction of what WMAP would detect was done by a non-DM theory. Whereas the predictions done by DM-theory (lambda 1999 model) miserably failed and only after the observations were obtained that the DM model was modified (pure curve fitting) to adapt it to the WMAP observations a posteriori.

However, the non-DM model predicted exactly the first and second peaks, i.e., before the observations.

This is pure, unadulterated fantasy. The dark matter model used in nearly all WMAP data analysis is the simplest possible: zero-temperature dark matter. This model fits the data exceedingly well. There is no curve fitting done with respect to dark matter in analyzing the WMAP data, except in terms of estimating the values of the various parameters. The simplest model for WMAP uses the following parameters:

1. Dark matter density.
2. Normal matter density.
3. Hubble expansion rate.
4. Scalar spectral index (an inflation parameter).
5. Optical depth to the CMB (basically, how transparent the universe is between us and the CMB).
6. Amplitude of fluctuations.

Each one of these parameters is physically-motivated. There is no "curve fitting" going on. Each one of the parameters which can be estimated independently with other experiments shows the same result for those parameters. The various extensions of this minimalist model, such as allowing spatial curvature to vary, or allowing the scalar spectral index to change with scale, so far show no evidence of deviation from this simplest description.

What you call «pure, unadulterated fantasy» is just the orange line in the next figure.

3peak06.gif


The orange line is the prediction done by the dark-matter model before WMAP data (and Boomerang data) was known. The dark matter model was clearly falsified... unless you are blind.

The prediction done by the non-dark matter model for both first and second peaks was remarkably verified... unless again you are blind. The third peak could not be explained because the model used then was non-relativistic, but some recent relativistic extensions seem to fit the third as well.

Once the WMAP data was known, DM cosmologists did an exercise in curve fitting (all of dark matter is pure curve fitting) and changed the parameters of the dark matter model until fitting the data.

Moreover, when forcing the dark matter model to fit the available data, DM cosmologists chose values for its free parameters that contradict other independent tests. For example, the baryon density assumed in the current dark matter cosmological model is much larger (about 3x) that the baryon density measured from other independent tests.

However, if you do not assume this high value of the density then you cannot fit the WMAP data using the dark matter cosmological model, generating a contradiction.

Therefore we have a contradictory dark matter model, which fails to explain many data (TFL, fine tunning of galactic rotation curves...) and whose hypothetical new kind of matter has been systematically not found in a large list of experiments performed since the 80s. I cited the recent results of Fermi not finding any evidence of the hypothetical dark matter, but before Fermi was Xenon100 the experiment that found nothing and before was...
 
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  • #20
juanrga said:
What you call «pure, unadulterated fantasy» is just the orange line in the next figure.

3peak06.gif


The orange line is the prediction done by the dark-matter model before WMAP data (and Boomerang data) was known. The dark matter model was clearly falsified... unless you are blind.

The prediction done by the non-dark matter model for both first and second peaks was remarkably verified... unless again you are blind. The third peak could not be explained because the model used then was non-relativistic, but some recent relativistic extensions seem to fit the third as well.

Once the WMAP data was known, DM cosmologists did an exercise in curve fitting (all of dark matter is pure curve fitting) and changed the parameters of the dark matter model until fitting the data.

Moreover, when forcing the dark matter model to fit the available data, DM cosmologists chose values for its free parameters that contradict other independent tests. For example, the baryon density assumed in the current dark matter cosmological model is much larger (about 3x) that the baryon density measured from other independent tests.

However, if you do not assume this high value of the density then you cannot fit the WMAP data using the dark matter cosmological model, generating a contradiction.

Therefore we have a contradictory dark matter model, which fails to explain many data (TFL, fine tunning of galactic rotation curves...) and whose hypothetical new kind of matter has been systematically not found in a large list of experiments performed since the 80s. I cited the recent results of Fermi not finding any evidence of the hypothetical dark matter, but before Fermi was Xenon100 the experiment that found nothing and before was...
Two points on this:
1. Did you even look at the parameters for the no dark matter case? Generally the parameters for these types of "alternative" theories are completely and utterly falsified by other observations.
2. WMAP has since measured the third peak pretty accurately, completely breaking the degeneracy between dark matter and the other parameters. The dark matter model fits, models without dark matter do not.

Edit: Oh, and let me just point out that the baryon density discrepancy is trivially explained by just noting that most of the normal matter has not fallen into gravitational potential wells and is thus invisible.
 
  • #21
Chalnoth said:
Two points on this:
1. Did you even look at the parameters for the no dark matter case? Generally the parameters for these types of "alternative" theories are completely and utterly falsified by other observations.

This remind me of a typical anti-evolutionist argument that says that fossils were put by God for testing the faith of the Christians.

It is not fascinating that whereas the DM prediction (red orange) failed miserably, the non-DM theorists were so lucky that used false values of parameters just to predict the result of the WMAP before was known. Those non-DM guys would play bonoloto all the weeks

Chalnoth said:
2. WMAP has since measured the third peak pretty accurately, completely breaking the degeneracy between dark matter and the other parameters. The dark matter model fits, models without dark matter do not.

Edit: Oh, and let me just point out that the baryon density discrepancy is trivially explained by just noting that most of the normal matter has not fallen into gravitational potential wells and is thus invisible.

As you said the evidence for dark matter is firm. It is so firm that numerous experiments designed to find it have all failed to find it merely for improving the true faith of DM-believers.

The measurement of the third peak is not so accurate as you believe and new experiments are being prepared to measure it with more accuracy. Of course, the third peak in no way proves that the dark matter is correct.

Edit: Oh and I believed that the baryon density discrepancy still remains unexplained in the literature, but you can give a reference on the contrary please.
 
  • #22
juanrga, please provide citations to demonstrate that your view has at least some currency in professional circles. If this is just your view, then publish it somewhere and make it part of professional discussion, and then we can consider it here.

If legitimate controversy already exists in professional circles, then it is fair game for discussion here; but this is not the place to start such controversy.
 
  • #23
juanrga said:
This remind me of a typical anti-evolutionist argument that says that fossils were put by God for testing the faith of the Christians.

It is not fascinating that whereas the DM prediction (red orange) failed miserably, the non-DM theorists were so lucky that used false values of parameters just to predict the result of the WMAP before was known. Those non-DM guys would play bonoloto all the weeks
You are truly demonstrating a shocking ignorance of the science you are so keen to criticize.

There is no unique power spectrum predicted for the CMB given the existence of dark matter. The specific power spectrum you get depends upon the amount of dark matter (and other things). However, dark matter produces an extremely distinct signature on the CMB power spectrum: it suppresses the even-numbered peaks with respect to the odd-numbered peaks.

This is why I went on about the third peak and why its measurement is important. It is possible to fudge the first and second peaks merely by adjusting the parameters which control how rapidly the overall power spectrum drops at smaller angular scales. But once you've measured the third peak, this degeneracy is broken, as now you can directly measure the overall decay of the power spectrum (by comparing the first and third peaks), and then if the second peak is comparatively low against this overall decay, then that is a definitive and conclusive signature of dark matter.

And that is precisely what we see in the data.
 
  • #24
jtbell said:
juanrga, please provide citations to demonstrate that your view has at least some currency in professional circles. If this is just your view, then publish it somewhere and make it part of professional discussion, and then we can consider it here.

If legitimate controversy already exists in professional circles, then it is fair game for discussion here; but this is not the place to start such controversy.

What you call «my view» is a well-known astrophysics/cosmological topic that has received large coverage even in science news services.

For instance, you can find some coverage about the most recent evidence against dark matter

http://news.sciencemag.org/sciencenow/2011/02/more-evidence-against-dark-matte.html?ref=ra [Broken]

http://blogs.nature.com/news/2011/02/post_73.html

Regarding the figure in my post #19 and my claim that the dark matter model predictions were falsified (orange line in that figure), take a look to http://xxx.lanl.gov/abs/astro-ph/0008188 (Astrophys.J. 541, 2000, L33-L36), you would find the first figure in page 10, which gives the correct prediction using a model without dark matter (No-CDM), whereas the second figure gives the well-known fiasco of the prediction done using a dark matter model (Lambda-CDM).

A review of a cosmology without dark matter is given in Class. Quant. Grav. 26: 143001, 2009 (http://arxiv.org/abs/0903.3602) although I do not like TeVeS.

If you search in this thread you would find my posts alluding to the null results by Xenon100 and by Fermi experiments in their search for the [STRIKE]aether[/STRIKE] dark matter. If you do not know what Fermi is or what measures, please search my posts here and follow the link to Physics World.

Now, it would be fine :rolleyes: if you also ask to Chalnoth to provide references supporting his many bold claims. He has just replied now to me but once again he refuses to provide references albeit I am asking to him for at least one...
 
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  • #25
juanrga said:
What you call «my view» is a well-known astrophysics/cosmological topic that has received large coverage even in science news services.

For instance, you can find some coverage about the most recent evidence against dark matter

http://news.sciencemag.org/sciencenow/2011/02/more-evidence-against-dark-matte.html?ref=ra [Broken]

http://blogs.nature.com/news/2011/02/post_73.html
What a bunch of steaming crap. Not one shred of evidence is presented here.

juanrga said:
Regarding the figure in my post #33 and my claim that the dark matter model predictions were falsified (orange line in that figure), take a look to http://xxx.lanl.gov/abs/astro-ph/0008188 (Astrophys.J. 541, 2000, L33-L36), you would find the first figure in page 10, which gives the correct prediction using a model without dark matter (No-CDM), whereas the second figure gives the well-known fiasco of the prediction done using a dark matter model (Lambda-CDM).
Except it doesn't fit. Not when you include the third peak. It is simply not possible to fit the first three peaks without dark matter.

I'd also point out that he simply has the wrong parameter values. That can be forgiven the paper's author because these parameters were not known in detail when this paper was written. The parameters are, however, known in detail today.

juanrga said:
Now, it would be fine :rolleyes: if you also ask to Chalnoth to provide references supporting his many bold claims. He has just replied now to me but once again he refuses to provide references albeit I am asking to him for at least one...
What, you want a textbook in basic cosmology? Here is how the various parameters impact the power spectrum of the CMB:
http://space.mit.edu/home/tegmark/cmb/movies.html
 
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  • #26
Chalnoth said:
You are truly demonstrating a shocking ignorance of the science you are so keen to criticize.

There is no unique power spectrum predicted for the CMB given the existence of dark matter. The specific power spectrum you get depends upon the amount of dark matter (and other things). However, dark matter produces an extremely distinct signature on the CMB power spectrum: it suppresses the even-numbered peaks with respect to the odd-numbered peaks.

This is why I went on about the third peak and why its measurement is important. It is possible to fudge the first and second peaks merely by adjusting the parameters which control how rapidly the overall power spectrum drops at smaller angular scales. But once you've measured the third peak, this degeneracy is broken, as now you can directly measure the overall decay of the power spectrum (by comparing the first and third peaks), and then if the second peak is comparatively low against this overall decay, then that is a definitive and conclusive signature of dark matter.

And that is precisely what we see in the data.

Unfortunately my «shocking ignorance» will remain because in each occasion that I ask you for a specific reference you offer me none...

It seems that you want to put in my writings stuff that I have never said (you can offer quotations if you believe the contrary), whereas you decidedly ignore what I have really said :uhh:.

As said before the third peak is still a bit controversial (foreground subtracting). As said also new experiments as PLANCK presumably will clarify this. Although you take WMAP third peak as gospel.

Moreover, the no-CDM model predicted the correct first and second peaks BEFORE the data was known. Whereas the Lambda-CDM model was falsified (see the orange line in the figure in #19).

AFTER and only AFTER the data was known the Lambda-CDM model was changed. I would not call that a prediction...

You go on and say that «is possible to fudge the first and second peaks merely by adjusting the parameters» in the dark matter model. I wonder if you read my posts because I already said this to you, but I added the important point of that values incompatible with other independent tests were assumed for the parameters. You claim that the «baryon density discrepancy is trivially explained» but then you fail to provide me a single reference showing that the discrepancy is solved.

You then go far and claim that overall measurement of the three peak ratios is «a definitive and conclusive signature of dark matter». Again this is another bold claim without support. First and second peaks are already obtained without appeal to dark-matter (in fact both peaks were predicted by a no-CDM model, see references given). The third peak can be explained without dark mater also, in fact you only need a source for gravity that propagates independently of the baryons. Precisely, this is the role played by the scalar field in TeVeS (although I dislike this theory by several reasons)
 
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  • #27
Chalnoth said:
What a bunch of steaming crap. Not one shred of evidence is presented here.

Yes Physical Review Letters and the several cosmologists and astrophysicists quoted in Science and Nature are well-known for their «bunch of steaming crap»:

Jerry Sellwood said:
The real strength of Stacy's paper is that it points to something that can't be explained in cold dark matter

Chalnoth said:
Except it doesn't fit. Not when you include the third peak. It is simply not possible to fit the first three peaks without dark matter.

He is merely a scientist and could not fit a, then inexistent, peak. Do you see the third peak in some figure in that paper?

It is possible to fit the three peaks without dark matter. But it is not possible to explain the other tests and observations that I cited before using a dark matter model.

Chalnoth said:
I'd also point out that he simply has the wrong parameter values. That can be forgiven the paper's author because these parameters were not known in detail when this paper was written. The parameters are, however, known in detail today.

As already said you this guy would be playing bonoloto :rolleyes:, because he is so lucky that using 'wrong' parameters he was able to predict exactly what would be observed in the experiment BEFORE the experiment was done.

He is so lucky :bugeye: that using a 'wrong' theory (i.e., one without [STRIKE]aether[/STRIKE] dark matter) and using 'wrong' parameters, he has been able to predict what has been after observed in hundred of observations/experiments. He has worked a whole spectrum from galactic scale to cosmos, and all his predictions have been posteriorly verified. ALL

Is not truly fantastic? Specially when his successes are compared with the failed dark matter predictions done about the same observations/experiments :uhh:

Chalnoth said:
What, you want a textbook in basic cosmology? Here is how the various parameters impact the power spectrum of the CMB:
http://space.mit.edu/home/tegmark/cmb/movies.html

Thanks by the laugh :rofl:. Now when you find some free time, please give me the specific reference asked. One is enough, do not send me 30 or 40, please
 
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  • #28
juanrga said:
He is merely a scientist and could not fit a, then inexistent, peak. Do you see the third peak in some figure in that paper?
No. That is my entire point. I see it in papers released today. For example:
http://arxiv.org/abs/1001.4635

The most recent WMAP data release shows a relatively tight measurement of the third peak, and a weak measurement of the fourth. Gone are the types of heuristic data checks performed by McGaugh: today we do full bayesian parameter estimation, and a universe without dark matter is conclusively ruled out.

juanrga said:
As already said you this guy would be playing bonoloto :rolleyes:, because he is so lucky that using 'wrong' parameters he was able to predict exactly what would be observed in the experiment BEFORE the experiment was done.
This is simply a blatant, unadulterated lie. He absolutely, positively, did not predict what the experiment would observe, because as you can see in the paper I linked above, the second and third peaks have nearly the same amplitude, while with McGaugh's parameters the third peak would have a much lower amplitude. He was wrong. And not slightly wrong. Completely wrong.

As for Planck, yes, Planck will improve our estimate of the CMB power spectrum, as well as shining light on quite a bit of other science. But WMAP measurements alone are more than detailed enough to answer the dark matter question.
 
  • #29
This thread is done. The article that juanrga is referring to is over 10 years. But, as Chalnoth says, we now have a lot more data giving us a far more detailed picture of the CMB power spectrum which simply cannot be fitted without CDM. As for MOND, I think very few people take this theory seriously anymore, and its relativistic generalisation also does not fit the data (e.g. http://arxiv.org/abs/0907.1463).
 

1. What is dark matter?

Dark matter is a type of matter that is believed to make up about 85% of the total matter in the universe. It does not interact with light, making it invisible to our telescopes and difficult to detect. Its existence is inferred from its gravitational effects on visible matter.

2. What is dark energy?

Dark energy is a hypothetical form of energy that is believed to make up about 70% of the total energy in the universe. It is responsible for the accelerating expansion of the universe and its exact nature is still not fully understood.

3. How are dark matter and dark energy related?

Dark matter and dark energy are two separate entities, with different properties and effects on the universe. Dark matter is thought to be responsible for holding galaxies together, while dark energy is thought to be causing the expansion of the universe to accelerate. However, their exact relationship is still unknown.

4. How do scientists study dark matter and dark energy?

Scientists study dark matter and dark energy through various methods, including gravitational lensing, galaxy rotation curves, and studying the cosmic microwave background. These methods allow scientists to indirectly observe the effects of dark matter and dark energy on visible matter.

5. Can dark matter and dark energy be explained by current theories?

No, current theories such as the Standard Model of particle physics and General Relativity do not fully explain dark matter and dark energy. Many scientists are actively researching and developing new theories to better understand these mysterious phenomena.

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