Comments on: Dark matter detected? http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/ I am an astronomer, writer, and skeptic. I likes reality the way it is, and I aims to keep it that way. My real name is Phil Plait, and I run the Bad Astronomy blog. Sun, 05 Jul 2009 20:00:51 +0000 http://wordpress.org/?v=2.3.1 By: Tissa Perera http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/#comment-83766 Tissa Perera Sat, 31 May 2008 18:04:43 +0000 http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/#comment-83766 Do not waste time trying to find Dark Matter physically. Go to my website 'cosmicdarkmatter.com' and I give a strong hint what the Dark Matter trick is all about along with a few more hints of Physics. /Tissa Perera Do not waste time trying to find Dark Matter physically.
Go to my website ‘cosmicdarkmatter.com’ and I give
a strong hint what the Dark Matter trick is all about
along with a few more hints of Physics.

/Tissa Perera

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By: the new shelton wet/dry http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/#comment-83765 the new shelton wet/dry Tue, 27 May 2008 20:30:28 +0000 http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/#comment-83765 [...] team of researchers in Italy are claiming to have directly detected dark matter particles. More: Half of 1/25th of the missing Universe is [...] […] team of researchers in Italy are claiming to have directly detected dark matter particles. More: Half of 1/25th of the missing Universe is […]

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By: G. Evans http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/#comment-83764 G. Evans Thu, 15 May 2008 17:20:16 +0000 http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/#comment-83764 I've read more skeptical assessments of the Italian experiment, and it appears that there are other, more likely, explanations for the observed signal. The whole dark matter issue is problematic. You say "we know dark matter exists," but that isn't true. What we know is that the current model of gravitational mechanics cannot account for the motion observed in large scale gravitational systems. There is no observational evidence otherwise of dark matter. To invoke dark matter is reminiscent of the concept of the ether. The ether was invoked to explain otherwise inexplicable observations. Ether failed as a useful concept, because the underlying thinking was flawed. It seems quite possible that the current thinking behind gravitational theory is flawed and that dark matter will go the way of ether and phlogiston. It is a disservice to science to make statements like, "we know dark matter exists." We know no such thing. I’ve read more skeptical assessments of the Italian experiment, and it appears that there are other, more likely, explanations for the observed signal. The whole dark matter issue is problematic. You say “we know dark matter exists,” but that isn’t true. What we know is that the current model of gravitational mechanics cannot account for the motion observed in large scale gravitational systems. There is no observational evidence otherwise of dark matter. To invoke dark matter is reminiscent of the concept of the ether. The ether was invoked to explain otherwise inexplicable observations. Ether failed as a useful concept, because the underlying thinking was flawed. It seems quite possible that the current thinking behind gravitational theory is flawed and that dark matter will go the way of ether and phlogiston. It is a disservice to science to make statements like, “we know dark matter exists.” We know no such thing.

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By: Richard D. Saam http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/#comment-83763 Richard D. Saam Thu, 24 Apr 2008 22:30:09 +0000 http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/#comment-83763 In regards to DAMA observed annual oscillation, a question comes to mind in terms of the following logic: What about the following logic: Given the statement: -- The Milky Way is moving at around 600 km/s with respect to the photons of the Cosmic Microwave Background (CMB). This has been observed by satellites such as COBE and WMAP as a dipole contribution to the CMB, as photons in equilibrium at the CMB frame get blue-shifted in the direction of the motion and red-shifted in the opposite direction. -- and also: -- the solar system is orbiting galactic center at about 200 km/sec -- and also: -- the earth has a velocity of 30 km/sec around the sun. -- and also -- ref: Dark Matter search http://arxiv.org/abs/astro-ph/0307403 Fig 10 Harmonic DAMA/NaI experimental data indicates an annual oscillation of detected radiation flux detected on earth. -- Has anyone done the trigonometry in order to calculate the correlation of annual DAMA/NaI experimental data on earth due to earth_solar annual differential velocity projection to CMB velocity vector? I have found some information to answer the question. Possibly you could comment. The CMB 'hot spot' or 'wind origin' is in constellation Leo http://aether.lbl.gov/www/projects/u2/ Now the earth moves around the sun at 30 km/sec The hypothesis would be that average flux would be when earth - sun line would be parallel to earth - Leo line which occurs September 1 (sun in Leo) and March 1. with maximum flux (earth against the CMB dipole wind) on December 1 and minimum (CMB dipole wind to earth's back) on June 1. This is 180 degrees out of phase with your data but perhaps that is a reflection of dark matter reality This CMB dipole wind and earth solar rotation are then approximately 180 degrees of phase with data expressed in: http://arxiv.org/abs/astro-ph/0307403 Fig 10 http://arxiv.org/abs/0704.3543 Figure 2 where t0 = 152.5 is ~June 1 (maximum flux) Is this a coincidence or an indication of connection between DAMA/NaI observed data and CMB dipole wind. I am interested in the above from the point of view that dark matter exists in congruence with CMB and critical space density as follows: m/B3 ~ critical space density 2 H2 / (8 pi G) = 6E-30 g/cm3 where: B = 22 cm m = 56 Mev/c2 (110 x electron mass) and may be a source of your observed annual DAMA NaI observation. In regards to DAMA observed annual oscillation,
a question comes to mind in terms of the following logic:

What about the following logic:

Given the statement:


The Milky Way is moving at around 600 km/s
with respect to the photons of the Cosmic Microwave Background (CMB).
This has been observed by satellites
such as COBE and WMAP as a dipole contribution to the CMB,
as photons in equilibrium at the CMB frame
get blue-shifted in the direction of the motion
and red-shifted in the opposite direction.

and also:


the solar system is orbiting galactic center at about 200 km/sec

and also:


the earth has a velocity of 30 km/sec around the sun.

and also


ref: Dark Matter search
http://arxiv.org/abs/astro-ph/0307403
Fig 10

Harmonic DAMA/NaI experimental data
indicates an annual oscillation of detected radiation flux
detected on earth.

Has anyone done the trigonometry in order to calculate
the correlation of annual DAMA/NaI experimental data
on earth due to earth_solar annual differential velocity projection
to CMB velocity vector?

I have found some information to answer the question.
Possibly you could comment.

The CMB ‘hot spot’ or ‘wind origin’ is in constellation Leo

http://aether.lbl.gov/www/projects/u2/

Now the earth moves around the sun at 30 km/sec
The hypothesis would be that average flux would be
when earth - sun line
would be parallel
to earth - Leo line
which occurs September 1 (sun in Leo) and March 1.
with maximum flux (earth against the CMB dipole wind) on December 1
and minimum (CMB dipole wind to earth’s back) on June 1.

This is 180 degrees out of phase with your data
but perhaps that is a reflection of dark matter reality

This CMB dipole wind and earth solar rotation
are then approximately 180 degrees of phase with data expressed in:

http://arxiv.org/abs/astro-ph/0307403
Fig 10

http://arxiv.org/abs/0704.3543
Figure 2

where t0 = 152.5 is ~June 1 (maximum flux)

Is this a coincidence or an indication
of connection between DAMA/NaI observed data and CMB dipole wind.

I am interested in the above from the point of view
that dark matter exists in congruence with CMB
and critical space density as follows:

m/B3 ~ critical space density 2 H2 / (8 pi G) = 6E-30 g/cm3

where:

B = 22 cm
m = 56 Mev/c2 (110 x electron mass)

and may be a source of your observed annual DAMA NaI observation.

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By: The AstroStat Slog » Blog Archive » Is 8-sigma significant enough for you? http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/#comment-83762 The AstroStat Slog » Blog Archive » Is 8-sigma significant enough for you? Thu, 24 Apr 2008 18:57:03 +0000 http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/#comment-83762 [...] of the direct detection of the effects of Dark Matter that is causing a lot of buzz. (The Bad Astronomer has a good summary.) They find yearly modulation in their detected scintillation rate that matches [...] […] of the direct detection of the effects of Dark Matter that is causing a lot of buzz. (The Bad Astronomer has a good summary.) They find yearly modulation in their detected scintillation rate that matches […]

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By: TMB http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/#comment-83761 TMB Wed, 23 Apr 2008 18:40:30 +0000 http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/#comment-83761 Oops, forgot my footnotes. ;-) 1: Don't get confused by the fact that the consensus is that we live in a "cold dark matter" (CDM) universe... although they both refer to the same aspect of dark matter (the relative velocity dispersion of nearby dark matter particles), the "cold" in CDM basically means that they're not moving relativistically, merely at a pedestrian 200 km/s. That's still plenty "hot" enough to keep them from clustering around the Earth, though. 2: This is known as the "Jeans mass", and is actually the same quantity that's used when talking about the collapse of gas clouds to form stars. In that case, it's the individual atoms in the gas cloud that are moving about (we normally call that temperature... see point 1 above), and you need a given amount of mass to have enough gravity to overcome a given temperature. Viggen, think of it this way: If you walk into a sprinkler, you'll get wetter than if you walk away from it. GR doesn't prevent water droplets from having a special direction with respect to the center of their distribution. Same thing with dark matter in a galaxy. [TMB] Oops, forgot my footnotes. ;-)
1: Don’t get confused by the fact that the consensus is that we live in a “cold dark matter” (CDM) universe… although they both refer to the same aspect of dark matter (the relative velocity dispersion of nearby dark matter particles), the “cold” in CDM basically means that they’re not moving relativistically, merely at a pedestrian 200 km/s. That’s still plenty “hot” enough to keep them from clustering around the Earth, though.

2: This is known as the “Jeans mass”, and is actually the same quantity that’s used when talking about the collapse of gas clouds to form stars. In that case, it’s the individual atoms in the gas cloud that are moving about (we normally call that temperature… see point 1 above), and you need a given amount of mass to have enough gravity to overcome a given temperature.

Viggen, think of it this way: If you walk into a sprinkler, you’ll get wetter than if you walk away from it. GR doesn’t prevent water droplets from having a special direction with respect to the center of their distribution. Same thing with dark matter in a galaxy.

[TMB]

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By: Count Iblis http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/#comment-83760 Count Iblis Wed, 23 Apr 2008 17:00:27 +0000 http://blogs.discovermagazine.com/badastronomy/2008/04/21/dark-matter-detected/#comment-83760 Excluding small subtle effects like the Ski season meantioned by Sean above somehow causing the modulation looks difficult. But there are a few reasons to believe that the detected effect is nontrivial. Apart from the detailed limits on background effects given by DAMA in their paper, there are a few things we can see from the data itself: 1) The amplitude and phase of the annual modulation are consistent with what you would expect from a DM signal. 2) The DAMA/LIBRA signal is within the error margin of the DAMA/NaI signal, except for a 2 sigma deviation in one energy bin. After dismantling the old apparatus, and installing the new detector and presumably making changes to other things as well, how likely is it for the alleged systematic error to cause a fake DM like signal within the bounds of the previously "detected" signal? 3) Absense of spurious signals. Sean's hypothetical ski season effect has a period of one year, but such an effect, however it is supposed to work, will generically have higher harmonics with relatively large amplitudes. The effect causing the detected signal does not. It seems to vary quite smoothly over the course of a year, consistent with how an expected DM signal should behave. 4) Absense of an annual modulation in the multiple hit signal. The DAMA/NaI and DAMA/LIBRA experiment use not one but a few detectors. Unlike weakly interacting DM particles, cosmic rays like muons have a significant probability of hitting more than one detector. By looking at the multiple hit events you can estimate the background. If the annual modulation were to be caused by variations in the muon flux you would see an annual modulation in the multiple hit rates as well. Another thing to think about: The DAMA team made public a very significant effect, but there are smaller effects like a diurnal modulation (caused by the rotation of the earth) that by now should be visible but are probably not yet statistically significant. If such signals turn out to be nonexisting in the future as more data comes in, then that would falsify that the annual modulation is due to DM. So, I guess that the DAMA team waited until they saw a diurnal modulation constent with what one would expect given the annual modulation and went ahead with announcing the annual modulation results. Excluding small subtle effects like the Ski season meantioned by Sean above somehow causing the modulation looks difficult. But there are a few reasons to believe that the detected effect is nontrivial. Apart from the detailed limits on background effects given by DAMA in their paper, there are a few things we can see from the data itself:

1) The amplitude and phase of the annual modulation are consistent with what you would expect from a DM signal.

2) The DAMA/LIBRA signal is within the error margin of the DAMA/NaI signal, except for a 2 sigma deviation in one energy bin. After dismantling the old apparatus, and installing the new detector and presumably making changes to other things as well, how likely is it for the alleged systematic error to cause a fake DM like signal within the bounds of the previously “detected” signal?

3) Absense of spurious signals. Sean’s hypothetical ski season effect has a period of one year, but such an effect, however it is supposed to work, will generically have higher harmonics with relatively large amplitudes. The effect causing the detected signal does not. It seems to vary quite smoothly over the course of a year, consistent with how an expected DM signal should behave.

4) Absense of an annual modulation in the multiple hit signal. The DAMA/NaI and DAMA/LIBRA experiment use not one but a few detectors. Unlike weakly interacting DM particles, cosmic rays like muons have a significant probability of hitting more than one detector. By looking at the multiple hit events you can estimate the background. If the annual modulation were to be caused by variations in the muon flux you would see an annual modulation in the multiple hit rates as well.

Another thing to think about:

The DAMA team made public a very significant effect, but there are smaller effects like a diurnal modulation (caused by the rotation of the earth) that by now should be visible but are probably not yet statistically significant. If such signals turn out to be nonexisting in the future as more data comes in, then that would falsify that the annual modulation is due to DM.

So, I guess that the DAMA team waited until they saw a diurnal modulation constent with what one would expect given the annual modulation and went ahead with announcing the annual modulation results.

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