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An interesting blog.  

https://tritonstation.wordpress.com/2018/08/09/the-next-cosmic-frontier-21cm-absorption-at-high-redshift/

I couldn't find the paper on arXiv only at nature.
https://www.nature.com/articles/nature25792

George H.  

Re: OT for other dark matter 'fans'.
George Herold did read
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We urgently need an other probe than EM radiation.
LIGO will teach us some things I hope.
And we should send probes looking for other planets,
see what the frequency shifts tell us, even to verify current
assumptions about redshift and bang.
And .. has a whole youtube presentation about multiple bangs.
(.. cannot remember his name).
So if (EM?) signals from one bang are present in the other then what.

For me it is clear, 'time started' is bullshit.
As there are more planets than earth, there are more stars than our sun,
there are more bangs than what they carry on about.


Maybe dark matter does not even exists, maybe grey matter well :-)
Dogma Einstein worshiping, peer reviews, expensive money grabbing, magazines.


Would be interesting to look what theories we have a million years from now,
or maybe there will be no humans, just mosquitos.

But, we need to go, to space, now.

  


Re: OT for other dark matter 'fans'.
On Saturday, August 11, 2018 at 12:59:38 PM UTC-4, snipped-for-privacy@nospam.org wrote:
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Hi Jan,  There is this 'debate' going on in cosmology/ astronomy about  
dark mater and MOND (modified gravity)  I'm just an interested observer;
But my understanding is that CDM (cold dark matter) fits with models of  
the early universe, (ripples in the CMB (cosmic microwave background))  
And that MOND makes a simpler fit to galactic models.  

The nature paper finds too much (21cm) absorption for dark matter models.
(Though they are looking for a signal that is hidden in a background that is 1k times larger...so might still be some calibration error...  
there is some nice stuff here.  
http://loco.lab.asu.edu/edges /))  

Anyway the blog author observes that it fits nicely with a  
'no CDM' which is very interesting.  

George H.
    
  

Re: OT for other dark matter 'fans'.
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I am aware of that, been following that for years.
Although the MOND theory, actually just an equation fix of Newton's,
is often shown correct, cases have been found where it is not.

There are other theories to explain red shift too, tired light was one of those.
Whole arguments in sci.physics when it was still about physics (stopped reading it).


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That is nice, did you have anything to do with that electronics?


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I have seen some nice presentations and an interview with Roger Penrose on youtube,
he is easy to listen too.

Why Did Our Universe Begin? - Dr. Roger Penrose - (Closer to Truth Interview)
 
https://www.youtube.com/watch?v=z2_6h15UCMg


Are we Seeing Signals from Before the Big Bang?" - Professor Sir Roger Penrose OM FRS
 
https://www.youtube.com/watch?v=npmDbbGbSoE


There is more, and there are also lectures from

There are also lectures by Leonard Susskind on youtube, he reminds me more of my physics teacher...

It seems some of Dr Penrose's theories regarding things we should see when there are multiple bangs are confirmed.
There is a lot of philosophy, that is good, we need that,

China now has the biggest radio telescope
 China's FAST telescope identifies 43 pulsars
  http://chinaplus.cri.cn/news/china/9/20180712/156701.html



Re: OT for other dark matter 'fans'.
On Saturday, August 11, 2018 at 2:32:39 PM UTC-4, snipped-for-privacy@nospam.org wrote:
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Right. I figure it's the second order term in some better gravity  
equation... lamda (dark energy) being the first term.  
We need the next Einstein. :^)  
  
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Nothing... I just found out about it from the trintonstation blog.  

Though it's pretty cool... you have to follow the redshift  
of the 21 cm line.. 1.5GHz down to z=~10,  ~150 MHz.  with some  
range so 500 - 50 MHz.  We (someone) should launch a ballon or  
rocket to look..  

A receiver on the dark side of the moon  
would block a lot of the Earth's RF interference.  
  
    
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OK I know little of Penrose.  I've watched a bunch of Susskind's  
videos.  (fun stuff)

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What's the frequency range?  

George H.  

Re: OT for other dark matter 'fans'.
On Monday, August 13, 2018 at 9:01:01 AM UTC+10, George Herold wrote:
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<snip>

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Penrose is interesting but perhaps a bit too willing to use his imagination.

https://en.wikipedia.org/wiki/Roger_Penrose

I've got a copy of  "The Emporer's New Mind" and I think I've bought and read "The Road to Reality" though it's not on our bookshelves here in Sydney.

A week or so ago I was walking through a C.M.Escher exhibition in Friesland (in the Netherlands) and got reminded of Penrose tiling, which influenced some of Escher's quasi-tesselations.

Penrose is more a mathematician than a physcist.

--  
Bill Sloman, Sydney


Re: OT for other dark matter 'fans'.
On 13/08/18 01:23, snipped-for-privacy@ieee.org wrote:

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I didn't realise it was that way round!

A couple of years ago there was the first(!) MC Escher exhibition
in the UK. It was well worth seeing, not only to be able to examine
originals close up, but also because the explanations were
enlightening - an example of excellent curation.

I've been entranced by his works since I first saw them in my
early teens in, of all things, one of my mother's magazines.
There's a lot to be said for boredom during school summer
holidays expanding minds.

Re: OT for other dark matter 'fans'.
George Herold wrote:
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Now you just wait until astron[a]uts from all countries in the world start hopping around there with their walkie-talkies :-)
China has interesting plans to put a satellite at the back side of the moon for communication with them astronauts
 http://www.planetary.org/blogs/guest-blogs/2018/0519-change-4-relay-satellite.html

 
https://www.youtube.com/watch?v=jgiEr13zkJo


 
https://www.youtube.com/watch?v=P52TKK2HtK8


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I do not know exactly, but from a 500m diameter disc one could infer it could still focus 6m (50 MHz) waves.
But no idea what sort or receiver they use, and if it covers that band.
  
Google and wikipedia to the rescue:
 https://en.wikipedia.org/wiki/Five_hundred_meter_Aperture_Spherical_Telescope
70 MHz to 3 GHz
likely because the illuminated diameter is a bit less than 500m, is 300m.

Re: OT for other dark matter 'fans'.
On Monday, August 13, 2018 at 3:04:48 AM UTC-4, snipped-for-privacy@nospam.org wrote:
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Huh, how do you get from 500 m diameter to 6 m waves?  (I know little  
about antennas.)    
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Well that is a perfect range.  Though the big problem may be interference...
which is why the EDGES thing is in the middle of nowhere...  
(Western Australia :^)  

George H.  
(me mum was from Perth)  

Re: OT for other dark matter 'fans'.
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50 MHz = 6 m

Now imagine a large mirror, 500m, and 6 m long waves hitting it.
Mirror is much larger than wavelength, a reflection pattern will form.

Same for audio, say ultrasound 44 kHz, just a small parabolic mirror will focus that sound.

Same for satellite dishes, say 10 GHz, 3 cm, a 300 cm dish will work wonders,
many are only about 87 cm, like the one I have.
Very narrow beam really, just point 1 or 2 degrees the wrong way and you lose signal.
 
http://panteltje.com/pub/xdipo-0.8.6.gif
 http://panteltje.com/panteltje/satellite/
lightning is:
 
http://panteltje.com/pub/bliksem_1.png
Do Not Wear Headphones Connected To Dish When Lightning Happens.


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Yes, nice place for an antenna, somewhere in the boonies
I still hope to see somebody receive alien TV programs...
That would change a LOT of things.
We see signals transmitted with  modern modulation systems look more and more like white noise.
We see tons of noise from the universe, it is very possible alien signals are not only part of that,
but maybe even a cause of that.
We use these modulation systems for better spectrum efficiency.
The math needed for decoding can be the big challenge.
I coded some dvb-s and it gives you a good idea what is involved.
 http://panteltje.com/panteltje/raspberry_pi_dvb-s_transmitter/
DVB-S is also what the voyager spacecraft uses.
But who knows, bit of luck is also needed, and political will to admit it,

  

Re: OT for other dark matter 'fans'.
On Monday, August 13, 2018 at 11:19:55 AM UTC-4, snipped-for-privacy@nospam.org wrote:
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Hmm, does it ever bother you that the transverse 'size' of a light  
wave is approximated by it's wavelength?  (which is it's length in  
time, so to speak.)  I always get a little weirded out when I think of  
tiny little atoms emitting or absorbing 'big' light waves.  
Worse still is proton NMR, flipping a tiny nucleus with  ~MHz 'light'.

George H.  
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Re: OT for other dark matter 'fans'.
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Yes, atoms absorbing and re-emitting energy:
From  
 https://en.wikipedia.org/wiki/Reflection_ (physics)
<quote>
 Mechanism
 In classical electrodynamics, light is considered as an electromagnetic wave, which is described by Maxwell's equations.
 Light waves incident on a material induce small oscillations of polarization in the individual atoms (or oscillation of electrons,
 in metals), causing each particle to radiate a small secondary wave in all directions, like a dipole antenna.
 All these waves add up to give specular reflection and refraction, according to the Huygens-Fresnel principle.
 In the case of dielectrics such as glass, the electric field of the light acts on the electrons in the material,
 and the moving electrons generate fields and become new radiators.
 The refracted light in the glass is the combination of the forward radiation of the electrons and the incident light.
 The reflected light is the combination of the backward radiation of all of the electrons.
 In metals, electrons with no binding energy are called free electrons.

 so the forward radiation cancels the incident light, and backward radiation is just the reflected light.
 Light-matter interaction in terms of photons is a topic of quantum electrodynamics,
 and is described in detail by Richard Feynman in his popular book QED: The Strange Theory of Light and Matter.
<end quote>


Is not 'atoms absorbing' just resonances? Electrons kicked to higher orbits?

In a mirror you _reflect_ the wave, it bounces of the surface in some specific angle,
the usually parabolic mirror is formed so the reflected waves all focus on some point.
 https://en.wikipedia.org/wiki/Parabolic_reflector
the wavelength is much much longer than the size of the atoms the reflector (dish) is made of,  
there may actually be holes in the mirror, as long as those are smaller than the wavelength.
You can make one from chicken wire for HF.
My satellite dish is an offset dish, so the receiver in the focal point (LNB Low-noise block downconverter)
does not cause a shadow on the reflector.

Acoustic mirrors are much the same, there it is air pressure variations,
 https://en.wikipedia.org/wiki/Acoustic_mirror
Molecules may heat up a bit will vibrate?

Same with the mirror in your flashlight (also EM waves) and in your car headlights,
but there the wavelength is much shorter, the atoms say in place (one hopes).

Math, play, neural net, understanding.

Filosphy..
Learning :-)

Re: OT for other dark matter 'fans'.
On Monday, August 13, 2018 at 1:40:59 PM UTC-4, snipped-for-privacy@nospam.org wrot
e:
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wrote:
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r it could still focus 6m (50 MHz) waves.
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wave, which is described by Maxwell's equations.
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tion in the individual atoms (or oscillation of electrons,
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ll directions, like a dipole antenna.
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ding to the Huygens-Fresnel principle.
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t acts on the electrons in the material,
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tion of the electrons and the incident light.
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of the electrons.
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,
ion is just the reflected light.
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rodynamics,
he Strange Theory of Light and Matter.
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ts?
Right, but atoms are tiny ~1nm and light is huge ~1um... how does that  
work?  (rhetorical question) Anyway it's mostly just me trying to think  
of quantum things classically.  
This is OK
https://briankoberlein.com/2015/04/14/thats-about-the-size-of-it/

George H.  
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cific angle,
n some point.
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or (dish) is made of,  
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han the wavelength.
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LNB Low-noise block downconverter)
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eadlights,
es).
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Re: OT for other dark matter 'fans'.
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work?  (rhetorical question) Anyway it's mostly just me trying to think
of quantum things classically.
This is OK
https://briankoberlein.com/2015/04/14/thats-about-the-size-of-it/
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Metals have much greater extents than ~1nm.  There is effectively a  
continuum of wavenumbers that are populated in any given metal, with the  
highest wavenumbers (lowest frequencies) corresponding to overall length, as  
we would classically expect.

Note that goes for the system-level, far-field approximation.  For near  
fields and direct current, of course, continuous electron displacement or  
flow is also a thing.

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
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Re: OT for other dark matter 'fans'.
On Monday, August 13, 2018 at 2:50:51 PM UTC-4, Tim Williams wrote:
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Right.  But take something like a Rubidium atom.  (Well I've got a bunch  
of them so I sorta know about them.)  Atomic radius is ~0.3nm but the  
cross section for absorption of resonant radiation.  (S-P transition  
of the outer electron) is something like the wavelength^2  
(divided by 2*pi or 4 or some term like that.)  Where the wavelength is
~795 nm.  
Where for something like Rayleigh scattering the cross section is tiny.  

How big a photon is, is something that has always bothered me a bit.  
I guess we only 'see' photons when the interact with something else..  
and so it's mostly the 'something else' that sets the size.  

George H.  
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Re: OT for other dark matter 'fans'.
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Yeah, high Q resonators couple much more nicely, don't they? :)

The classical equivalent is a very small, very narrowband, but still  
reasonable gain antenna.  Like a Tesla Coil (but designed for enough Q (and  
not sparking) so that the far field radiation resistance dominates its real  
component).


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Well, photons have zero mass, while everything else has nonzero, so, the de  
Broglie wavelength certainly works out that way. :)  The atom might be very  
small, but convolved with the photon PSF, you can't tell.

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
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Re: OT for other dark matter 'fans'.
George Herold wrote:
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OK site indeed.
I look at it (Einstein now rolls over in his grave) as a ball on the water
No matter how long the wave (length), the ball will move up and down with it.
I know E says no ether, about the M&M (not the candy) experiment, etc  
but there is a medium, else why Mu0,
physics now talks about virtual particles popping in and out of existence,
but 'virtual' and 're-normalization' is a hint they got it, as also often happened in history,
100% wrong.
I was reading this today:
 https://www.sciencedaily.com/releases/2018/08/180809112435.htm

Re: OT for other dark matter 'fans'.
On Monday, August 13, 2018 at 3:11:24 PM UTC-4, snipped-for-privacy@nospam.org wrote:
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Hmm I've heard people talking about accelerating electrons with lasers for  
a long time.  Getting all the timing right is the hard part.  
(linear accelerators are kinda a string of microwave cavities.. with the  
microwaves put in at just the right time and phase... doing that with  
light waves is harder.) but who knows maybe they have some good ideas.  

George H.  

Re: OT for other dark matter 'fans'.
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What fascinates me is that if you wiggle an electron here at say 1 GHz,
then EVERY electron in the known universe feels the effect of that.
That is where is that analogy with the sea and the waves and the ball comes from.
Throw a ball in here, and the waves will propagate, and move a ball elsewhere a bit later.
That requires a medium, water molecules in this case, H and O atoms combined, quarks, how deep can you go?

When I wiggle that electron with 1 GHz,
and use a very precise 'electron pendulum, say tuned circuit, electronic tuning fork' on mars,
then that will also start swinging at 1 GHz.
That is our radio principle.
And electrons reject each other.
And we do not know the exact size of an electron.
One would then think something must be flowing out of them electrons so they reject each other.
Like a little sun?
Electron a much more complex thing, really we do know shit.
Einstein and field equations are just a way we ants describe the walls of the houses they creep up to.
That is why I take all physics theories with a big container of salt.

But we play with them electrons, and we are its play.

Re: OT for other dark matter 'fans'.
On 14/08/2018 08:14, snipped-for-privacy@nospam.org wrote:
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Eventually - after the wave has had time to propagate there and subject  
to an intensity that falls off as the inverse square law.

One thing to ponder is that to have a precise well defined frequency f,  
the photon must exist over a length of time t along its trajectory that  
is sufficient to enclose a respectable number of cycles to make df  
small. Otherwise the frequency becomes ill defined as in ultra short  
laser pulses. I stumbled upon this rather lovely review article whilst  
looking for an example (it even mentions regen optical amplifiers):

http://www.ull.rdg.ac.uk/documents/ULL_Antoncini.pdf

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Ether theories went out with the ark. Michelson-Morley experiment showed  
there is no medium for electromagnetic waves beyond spacetime itself.

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Although we can put experimental bounds on its size being at least  
10000x smaller than a proton or neutron. Experimentalists are working to  
refine that further but it requires a lot of energy to see fine detail.

And HEP is like studying the workings of chronometers by smashing them  
together at ever greater speeds. But at least unlike astrophysicists the  
HEP guys can manipulate their experiments on Earth - we just have to  
take what we are given and look at it carefully from a distance with  
whatever tools we can muster. These days most wavebands are possible!

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Like charges repel, unlike charges attract. It is one of the things that  
makes gravity different - matter and antimatter both attract each other  
through gravity and any electric charge they might have.

Merging gravity with all the other physical theories remains one of the  
most awkward problems for modern physics. It may be the weakest of the  
forces of nature but it certainly causes the most difficulties to GUTs.

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Physics is just the best model of the universe we have at the present time.

It is always subject to revision when a new experiment demonstrates that  
the current theory makes an entirely wrong prediction. Designing such  
experiments to break the status quo is the stuff of Nobel Prizes.

--  
Regards,
Martin Brown

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