Author Topic: Dark matter  (Read 44150 times)

paulrogers

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Re: Dark matter
« Reply #465 on: April 20, 2012, 10:21:19 pm »
I just ran into a similar article here.

graham d

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Re: Dark matter
« Reply #466 on: April 21, 2012, 08:46:00 am »
Yes Paul it's a similar review about the Bidin et al paper in  http://arxiv.org/abs/1204.3924
The implications are so profound that it will stir up controversy. Sean Carroll tries to make light of it over on
http://blogs.discovermagazine.com/cosmicvariance/2012/04/20/puzzles/
whereas Mond enthusiasts will welcome the result. Who is right?

Remember that almost everyone is sold on creation theory. After 45 years, as an analogy with canonical certainty, one accepts the creed
(1) the Big Bang  (2) the CMB 380,000 post creational afterglow (3) the 3 pillars of structure- flatness, horizon problem..inflaton fields...(4) WMAP highest ever measurement precision of thermal density fluctuations  (5) the mass balance ~5% normal matter ~25% dark matter, ~75% dark energy.

 The creed though does evolve with time- it is science, although in the telling the numbers get confused as in these reviews where they bandy 80% dark matter by incorporating dark energy.

?(6) accelerated expansion from SN1 supernovae data.

Galaxies or rather clusters and superclusters  infact are observed to  fly away from each other. They must therefore be closer in the past. There is further subtlety that space itself is expanding and not the analogy that movement is through space. Then there is the chemistry- too much helium around than to have been forged in the low temperatures of stellar cores at a significant rate. Weak force conversions of protons to neutrons are incredibly slow, ca 10 billion years for each proton to flip to a neutron even at 20 million degrees; our bodies create more heat to maintain ambient temperature!

Gamow's realisation was that we had a hot beginning and there would be a thermal signature left behind with continued expansion from a tiny spatial beginning. Even prior to this Eddington came up with a 3 Kelvin "afterglow". Nobel awards subsequently litter the development of this creed at step 2.
 
Penzias and Wilson's empirical measurement of the radio/microwave excess radiation is bedrock- it exists; no argument here. It's the interpretation that  can be challenged. The creed accepts it is relic or fossil radiation, an afterglow from a time 380,000 yr after the creation event, less than a million years from a beginning whose own timeframe is measured at about fourteen thousand million fold from our own epoch, ~before the common epoch. Each photon has been travelling all this time without interaction; it hasn't thermalised and preserves its thermodynamic equilibrium distribution to better than 1 part in 100,000 even though the radiation is no longer in thermal equilibrium. The creed accepts this stretching of wavelengths as inversely related to the scale of the expansion. The photon distribution in an expanding space loses energy even though one has to sacrifice one of the dearest principles we own, the second law of thermodynamics.

The accepted creed evolves. We may bandy numbers; is it 4.5% normal matter, 83% dark energy?, new accelerated expansion to a heat death?. We like beginnings and ends in the Judeo Christian enclaves. There are variants even within the accepted creed- cyclic universes, other universes, hardly scientific rigour; times before the Big Bang infact which are obvious heresies if you accept that not just space but time itself arose from a Big Bang singularity, the cornerstone of this creed.

It's a pity that the concomitant Ice Cube results last week didn't reveal the anticipated high energy neutrinos from WIMP decay.
The creed developed from a time when the standard model left hand neutrino was thought to be massless. For the last 25 years it was speculated to have restmass, tiny by comparison with it's electron lepton cousin at 511,000eV, massing in at no more than 20eV. Cosmological analyses brought that massenergy down to no more than say 0.5eV. Minos came up with two results, both astounding; a cumulative mass of the three flavours at about <0.05eV but a doubtful mass squared energy difference that is still regarded as a problem, a statistical problem that will go away perhaps. Silence since February 2011.

 Neutrinos have such low masses <0.05eV that their cosmological effects can be observed, as I have discussed ad nausea, at length that there is a new interpretation of the CMB and indeed the validity of the Big Bang.

 We live in exciting times.
« Last Edit: April 21, 2012, 08:58:02 am by graham d »

paulrogers

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Re: Dark matter
« Reply #467 on: April 21, 2012, 04:05:23 pm »
Well, no, I'm still skeptical of that "creed" entire.  This is Science, after all.  When those so-called tachyons made the news recently, there was some doubt that it might be true.

For me, it's the old "'Beauty is truth, truth beauty'---that is all ye know on earth, and all ye need to know."  We've seen that works in Science.  I think the same can be said of Simplicity, as in Occam's Razor.  It just seems to me that we're getting too many "epicycles" on our cosmology, if you take my meaning.
« Last Edit: April 21, 2012, 04:07:56 pm by paulrogers »

graham d

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Re: Dark matter
« Reply #468 on: April 22, 2012, 05:19:32 pm »
Just back from the allotment with a couple of hours to kill.

I'm not sure what your meaning actually is Paul. Helios refers to Greece or Hellos. The Ptolomaic system was wrong, Copernicus was correct. From hindsight, although I doubt anyone has used it, after the fact we may refer to it as heliocentric dogma. Can we refer to our current understanding of the cosmos origin as cosmological dogma?

Within the last 6 months there has been the greatest turmoil happening in the history of Science. There have been thousands of archived and published papers on tachyon neutrinos; there wasn't some doubt individually, collectively there was huge doubt. Again thousands of theories on Susy have been trashed by the LHC exclusion energy ranges reported almost on a monthly basis. In the history of Science never has there been so much carnage; mega brains the likes of that robot in Hitch Hikers Guide, reduced to menial tasks and utter depression. Last week woeful news in that the anticipated flux of high energy neutrinos from gamma ray bursts failed to materialise in the Ice Cube South Pole experiment! If only we had known that in the late 60's.

This isn't science in general; it's all about hard physics and mathematics. There may be a lot of worries about the increase of pseudoscience or antiscience. When we talk about particle physics or dark matter and its implications to cosmology, the history that takes us to current views about standard models in either fields it is a comedy of errors and changing viewpoints, often radical personal changes of view in particle physics but things are quiet on the cosmology front.

It's not that you know too little science, infact you know too much. There's no simplicity here in hard physics. Occam's razor led many a particle physicist astray. Much of the theory is counterintuitive; it's not simple and it isn't Occam's razor in tortuous old English. There are many scientific disciplines. A decade ago a can of sardines or a glass of red wine was good for you, nowadays it isn't; it could be a statistical 10% enhanced chance of whatever proves mortal. Even aspirin gets a lousy press from time to time; if you are Japanese it's likely to kill you. In the end it's a lottery; you have good genes or bad ones but infact science will infact prolong your life regardless of any placebo effect based upon philosophy or religion.

Early on in this thread I mentioned that with regard to the Standard Model of particle physics and extensions to it, such as a master symmetry to U1 and SU's 2 and 3 there was no other game in town, regardless of the invective about stringers string theories or membranologists which I don't intend as a derogatory comment. The Standard Model is incomplete, nevertheless it's more complete this month than ever so before. Three years ago I mentioned that the Higgs Boson was 90% or 99% certain to exist and to be discovered. Within the last year the Cern director was a worried man, as the exclusion zones broadened it looked like they wouldn't find it, so how would they disclose this news to the public who had forked some10 billion euros? Susy particles as well faired badly. Paradise was regained when it is now apparent there could well be a standard model Higgs discovery. Nothing is certain, it could be Radion!

Particle physics, and I may add also in the development of cosmolgy, is and was awash with triple A brains. Not all. Peter Higgs has taken a lot of flack in the last 45 plus years. He is a very modest man, and that is unusual. You all know he wasn't the first in the game etc. , there were others , three in mind and at least half a dozen other contributors, and much much odium and strife in the ensuing years. However, he was the first to mention what the others omitted, namely that quantum field theory implied with every field, that there was an associated force carrier and as an excitation of the field, that there was a real particle associated with it, a spinless scalar boson, Goldstone's 4th boson. Some claim it was obvious at the time. Infact, this was all before people were writing SU(3) maths. Quantum field theory was in the doldrums at the time, some Nobel Laureates, perhaps the most famous one you are familiar with  so I'll not mention his name(s) rubbished it and the idiot perpetrators of such theories. If you publish enough papers some you will get right and others will be wrong. The bad ones are forgotten.Folk remember your best stuff.

There's one paper I published in '74 in Chemical Geology but I never mention until now; it had a huge error I should have realised at the time but didn't. The empirical results revealed that the isotope ratios for two metals nickel and chromium were of solar and meteoritic abundance. The conclusion was that >ca. 3 billion years ago huge astrobleme impacts had reset the terrestrial ratios, that were hugly different. This was 1974, well before any iridium anomalies in the Cretacous Tertairy boundary were mentioned. I was eventually correct about the implications to theory, but many months later some South African geologists redid the experiments on the South African Cherts from Swaziland and proved my results were erroneous. I redid the analyses with another procedure and lo and behold they [South African  ] were correct. The new theory that there were major astrobleme impacts that caused the arcuate geological structures in the Early Precambrian was regarded as wrong. Instead they were vindicated as accepted volcanic dogma. Of course I got the theory right in hindsight but based upon a lousy procedure for these metalextractions. This is the first time I have ever admitted to it. Folk do forget your bad papers, but you can't and closet them for years.

In the development of the Standard Model and Peter Higgs huge contribution, apropo hidden symmetries and the mantra of spontaneous symmetry breaking to it, amidst the arrogance abrasiveness and agression of all participants to it over the years,  regardless of whether it exists or not, and post the discovery of the top quark it almost assuredly does exist, then Peter Higgs thoroughly deserves that Nobel award, above all others as soon as possible. It is not awarded posthumously and the shame that would ensue otherwise is and would be immeasurable.

You know too much science, not too little. A strange comment perhaps. It is axiomatic and an axiom is a rigorous term to a mathematician that particles are produced in pairs. Weinberg applied the principle to cosmology during the infancy of what became the Standard Model not just of particle physics but of Big Bang cosmology. It is not easy to forget what you have learned. Time travel back to Hubble's day when he elaborated upon what Vespto Slipher had noted for misidentied galaxies. They were receeding from each other. Hubble's law was based upon locally distant galaxies and his plot I commented on before was pathetic. OK- fast forward ; his theory was correct although his observations had they been appropriate for planetary motions would have left one screaming for Ptolomy's system. I tend to think that were he here now he would observe that  all those filamentous structures and triple junctions were not what he envisaged, except that once one gets to 100 fold his original distances then yes they all appear to be receeding from one another out to what is observable. Out beyond 100-200 megaparsecs then yes it's expansion even though there's the odd group still being incorporated into large clusters.

Let's go back to the mid seventies and Weinberg's Big Bang model at the time of the eight fold way or before what has become the Standard Model of Particle physics. There were two flavours not three, the strange quark has been discovered but not the charm, far more massive and much longer lived; half the eventual cluster of quarks. In Weinberg's model there are two neutrinos and these are massless. The Standard Model treats massless left handed neutrinos; but does it? Already there were doubts; could neutrinos have restmass in the same manner if I might ask today, do gluons have a mass charge? Try answering that one or why is the electron mass what it is? The quarks inhabit a nuclear region down at 1000 to 10000 fold of the atom radius. So as per orbiting electrons why don't quarks do likewise. Pauli had his exclusion principle. These are fermions and it couldn't happen. Counterintuitively, colour charge, three of them, was introduced so they could accommodate themselves. Furhermore,  and weird , unlike the screening problem for electrons the quarks displayed what was called asymptotic freedom mathematically or  anti screening. This wasn't simple and it took a then mathematician who was rapidly morphing into a particle physicist , Frank Wilczek, to do it; renormalised Yang Mills equations with a negative force function. Gerard 't Hooft, a young post doctorate did it previously but didn't know or realise the implications that would have won him a second Nobel much earlier in his career. Counterintuitive and complex, not simplicity itself that put field theory back on the map in a maths backwater of U1 SU(2) SU(3) symmetries, a rag bag of chalk and cheese symmetries, U1 is not on killing's list, not the beauty of Dirac's visions.

Weinberg treated massless neutrinos that as per photons lose energy as an expanding universe evolves. A hot beginning, a cooling evolution; there should be thermal imprint of stretched photons and neutrinos in the hereafter.; a CMB neutrino temperature lagging ca. 40% below a photon temperature background, but we can't measure it yet. Remember real particles don't stretch; their rest mass remains constant. Weinberg treats particle pair production for electrons and positrons but beyond heavier mesons there are just too many particle types to treat. Effectively, he starts with a hot universe at ca 4 light years in extent at ~1011Kelvin, although the universe could be infinite in extent and follows pair production temperatures and equilibrium conditions of photon abundances and particle pairs in a continuum of energies, a black body distribution of radiation that the particle physicists are aware of. There are non equilibrium events; eg. electron positron pair instabilities or gamma ray bursts where you expect to see discrete energies and not thermalised continuae in our current cold universe. There are the three problems I alluded to that inflation settles although one has to accept an immense alternative, the singularity of almost infinite density. Well the Vatican goes along with it but I don't suppose they understand the second law.

There's counterintuitive stuff here. Just why is there this huge photon abundance and a smattering of baryonic stuff left after annihilations. Why is the electron mass and charge what it is? Thee fold higher and there's no existence; everything collapses into neutrons fast; there are no atoms. Threefold less mass and charge and yes there are atoms but they are sluggish and bigger. Today we have small stars half our sol's mass that will burn for another 300 billion years; ours another 5 billion and before that the Goldilocks zone has disappeared. But we need heavy elements for our existence and without rapidly burning heavies there's no carbon , no oxygen etc that makes our example of sentient life possible.

However, neutrinos were speculated to have mass and were given mass, a very small mass. Let me add that the measured mass squared differences that were predicted by Carl Brannen's extension to Koide's remarkably accurate theory for the three flavours of lepton masses, despite our inability to understand its deeper meaning as per a Balmer's formula analogy, predicts the neutrino masses. Or rather the phase angle analogy to Weinberg's angle for quarks predicted a phase called delta =2/9 + Pi/12 for neutrinos. Minos produced a strange result in June 2010 as well for the antineutrinos that agreed with Brannen's theory were the phase angle 2/9 - Pi/12. Let's say d=a +b . Marni Sheppeard shrewdly noted that for phase angle d=a-b the antineutrino mass squared difference value conformed to the Minos measurement . From this thread I was familiar with such low energies and/or rest mass energies and chiralities. Neutrinos had mass, low mass at that and quick calculations as per Weinberg revealed an answer, impossible initially to comprehend. Photon neutrino pair production meant it was axiomatic that these real and not virtual particles would be produced from the vacuum and cosmologically observable at current temperatures of a few orders of magnitude. I'm an atheist, most days, but I pondered why a creator would choose a +b and then a-b; why not counterintuitively since it has to accord with that Standard Model axiom, why not plus or minus a and  plus or minus b? Infact not just one or two but four per flavour making twelve in all. It is not simple and it is not Occam at all. Marni's mirror particles were born which I continue to propose allo. Meanwhile Minos remains silent, and hopes it is an anomaly and will go away since nobody likes Koide's representations. Why should a radically different interpretation challenge cosmological dogma? I do not believe that this continuum pair production temperature is coincidence. It predicts an antineutrino photon continuum temperature  of 2.73 Kelvin! for the first flavour electron antineutrino for parity conserved L and R spins. It will take a long time for the penny to drop perhaps for cosmologists with litlle particle physics knowledge. It's more likely a particle physicist will take note. You may be familiar with Popper; it's no virtue on my part to claim I have never read his books. Marni represents the predicted maths in her form; I see it as a physical chemist or an organic chemist would, well 24 order tetrahedral chirality is pushing it perhaps; that was my graduate and postgraduate background for many years. Is it correct? If it is verified our present understanding of cosmology will be akin to Ptolomaic epicycles of cosmology.
 
The vacuum is not just a seething mass of virtual particles striving to become real but is real particles of photons and neutrinos, even at the present day low temperature. What Penzias and Wilson measured is not a relic radiation but a here and now living vacuum of real particle pairs with differing mass charges that can annihilate amongst themselves as neutrinos and antineutrinos but also their allo or mirror  pairs. They don't cross annihilate. Why? because we would observe a hybrid temperature not at 2.73Kelvin and as a an axiom , they don't carry electric charge or the colour charge. Instead if we accept Minos initial results that were prtrayed as the end of physics at the time they carry different mass charges so they cannot annihilate.This equilibrium continuum as implied as an implication is continually generated in an expanding universe with a density of ca. half an electron mass per cubic metre, much smaller than ~6GeV of baryonic particles/m3. Weinberg's worry or enigma disappears, lepton number is conserved and the tiny baryon to photon ratio comes from the misidentification of the CMB with relic radiation, is now seen as a 1:1 correspondence of neutrino pairs with photons. This isn't conjecture it is a proof. Neutrinos have mass, they are real particles and have a pair production temperature threshold. Were we not to know of Penzias and Wilson's result nor even the  Higgsy diphoton result we would predict that there is a true present day excess thermal noise equivalent to a black body spectrum at 0.89Kelvin or 2.73Kelvin derived from the continuous creation and annihilation of these now massive neutrinos. Now go find this CMB radiation. Thus I jest. The Penzias and Wilson and WMAP experiments did perform. Almost 14 billion years later the radiation never thermalised but still retained its Planck black body profile to better than 1 part in 105. That took some swallowing and is still infact accepted. That is what you and everyone bought , most passively- there was no alternative; neutrinos didn't have mass and if so were much heavier, or at least<20eV. 

Without a knowledge of neutrino masses there was no other interpretation of the origin of it other than as relic radiation that was never thermalised. It had to keep its distribution as a relic effect in which a universe expanded faster than it could thermalise. If you play it according to Popper then the conventional interpretation of the CMB radiation has been falsified by particle physics data that could scarce have been dreamed on some 50 years ago. The Steady State model attempt  to thermalise this so called relic radiation was forlorn hope and still remains so. Neutrino oscillation and photon pair production provides a new cosmology radically different from the Big Bang. We live in an ageing universe but it is still being created, everywhere in every nook and cranny! That's what the Minos mass squared interpretations allude to. The second law tells us that this mass balance of creation must be balanced by a concomitant destruction of space and its ancient baryon contents. The only place for it to disappear appears to be in black holes. Protons don't evaporate below immense time scales of 1032 years.

There's real beauty here and a much richer and newer cosmology predicted for a halfway universe between an infinite existence of mostly eventual heat death and one of non existence at all, where sentient life can never evolve, where heavier elements never get forged. 1/alpha or 137 (137.036 that runs) and tiny neutrino masses appear as midway constants and not fine tuning, fuzzy , middling values conducive for life in our observable part. The potential vacuum energy at up to 10 120 the cosmological measured density at 2.73K is cancelled out to leave us with a virgin spacetime vacuum of close to half an electron mass 250,000 eV/m3 compared with the critical density of ca. 6 GeV(6 thousand million eV0/m 3; ~1/28000 . I envision it as a Halfway Universe as in halfway home. We may speculate it doesn't have a beginning nor an end, nor is it cyclical in the currently accepted sense. Existence versus non existence, end members of philosophical torture. We live in the here and now with the 2.73 Kelvin glow of new growth around us. Elsewhere for some it's 0.89Kelvin. Space has to collapse somewhere for the glow from the other neutrino flavours. There has to be compression elsewhere and indeed from where comes the new baryons to replace the old. That's a hard nut to crack. We do need Weinberg's 4 light year continuum conflagrations ~1011K , not bremsstrahlung gamma ray bursts with redshifted high energy neutrinos, the very types the Ice Cube expected to detect. At supercosmological distances events, such as enormous energy production as gamma ray bursts at near light  velocity in its own reference frame , would to us in our reference frame for an event that takes several seconds might take years (up to~4 light years?) to develop in that far distance reference frame. A lesser effect is noted with closer supernovae at cosmological distance( not to be confused with super cosmological distance). About 150 events or grb's are registered here each year. In the Weinberg model, in this epoch the high energy neutrinos are in equilibrium and are thermalised. Volcanic eruptions herald the creation of new crust in a constantly rejuvenated Earth. I don't intend to rid the universe of Big Bangs at all. No-within our own universe, not a multiverse is required, it appears likely that these represent Weinberg type conflagrations, happening once every two days :), there's one born every day in our reference frame, and not a once and for all time event that only ever happened once some 14 billion years ago.


« Last Edit: April 22, 2012, 11:10:11 pm by graham d »

graham d

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Re: Dark matter
« Reply #469 on: April 22, 2012, 11:24:53 pm »
There's real beauty here and a much richer and newer cosmology predicted for a halfway universe between an infinite existence of mostly eventual heat death and one of non existence at all, where sentient life can never evolve, where heavier elements never get forged. 1/alpha or 137 (137.036 that runs) and tiny neutrino masses appear as midway constants and not fine tuning, fuzzy , middling values conducive for life in our observable part. The potential vacuum energy at up to 10 120 the cosmological measured density at 2.73K is cancelled out to leave us with a virgin spacetime vacuum of close to half an electron mass 250,000 eV/m3 compared with the critical density of ca. 6 GeV(6 thousand million eV0/m 3; ~1/28000 . I envision it as a Halfway Universe as in halfway home. We may speculate it doesn't have a beginning nor an end, nor is it cyclical in the currently accepted sense. Existence versus non existence, end members of philosophical torture. We live in the here and now with the 2.73 Kelvin glow of new growth around us. Elsewhere for some it's 0.89Kelvin. Space has to collapse somewhere for the glow from the other neutrino flavours. There has to be compression elsewhere and indeed from where comes the new baryons to replace the old. That's a hard nut to crack. We do need Weinberg's 4 light year continuum conflagrations ~1011K , not bremsstrahlung gamma ray bursts with redshifted high energy neutrinos, the very types the Ice Cube expected to detect. At supercosmological distances events, such as enormous energy production as gamma ray bursts at near light  velocity in its own reference frame , would to us in our reference frame for an event that takes several seconds might take years (up to~4 light years?) to develop in that far distance reference frame. A lesser effect is noted with closer supernovae at cosmological distance( not to be confused with super cosmological distance). About 150 events or grb's are registered here each year. In the Weinberg model, in this epoch the high energy neutrinos are in equilibrium and are thermalised. Volcanic eruptions herald the creation of new crust in a constantly rejuvenated Earth. I don't intend to rid the universe of Big Bangs at all. No-within our own universe, not a multiverse is required, it appears likely that these represent Weinberg type conflagrations, happening once every two days :), there's one born every day in our reference frame, and not a once and for all time event that only ever happened once some 14 billion years ago. I forsee neither a beginning nor an end, that we cannot forsee either a beginning of time along that vast abyss of history nor the prospect of an end. Can one comprehend a new star born every day somewhere in this vast local group :)? Well yes that's what we learn to do on galaxyzoo. 1011 galaxies, that's a huge number to fathom. So too is 1018 grb's or rather GRB's but only another 7 orders. Worse still is the comprehension of 20,000 character limit for a post.


Bruno

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Re: Dark matter
« Reply #470 on: April 23, 2012, 02:47:17 pm »
Quote
Worse still is the comprehension of 20,000 character limit for a post
must be some superior will...... ;)
Ciao
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paulrogers

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Re: Dark matter
« Reply #471 on: April 24, 2012, 06:31:15 pm »
Graham, what I was hinting at was the Ptolemaic system worked as a rough first approximation for a long time when nothing better was known, but in order to continue to use it and account for that fact that it was a fundamentally wrong view of the solar system so its predictive value failed more precise measurements, it had to be "embroidered" with complexity, epicycles, and epicycles on epicycles.  Eventually, because it was fundamentally wrong, it had to fail.  But it's history made it more difficult for people to accept a Copernican system than it had to be.

And then we have the point Feynman addressed in his lectures that elemental particles like photons and electron are something we cannot understand if we insist on thinking about them in familiar terms, i.e. wave-particle duality.  As I believe he said, they are nothing like anything we know.  That being true, I have reservations about accepting our ideas that mass, charge, spin, etc., are their "fundamental properties".  They're just the ones we can sense and measure.  It's like there's a hint that these things exist on some higher dimensional "plane" where their fundamental properties exist, and they only interact with our space-time in the "limited" ways that we can observe.  Maybe that's why we've got this disconnect we're trying to identify with dark matter and dark energy.  I'm not willing to stipulate we'd ever be able to figure out what their true fundamental properties are when they're at home, or that any scientific experiment in space-time could reveal them unambiguously, but I am willing to hold these reservations that there's another explanation that ties everything up beautifully and neatly, as we've come to expect of scientific theories that really work on grand scales.

And since that cannot be proven by experiment, it's non-scientific.  I'm not even sure I can call it a "belief".  But knowing about the Ptolemaic-Copernican transition, and what I perceive as complexities of (if not glitches in) the current Standard Model, I would be ready to chuck the Standard Model if something simpler comes along.  Granting I could recognize something simpler. ;)

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Re: Dark matter
« Reply #472 on: April 26, 2012, 02:43:32 pm »
Occam's Razor.  Simplest explanation.



God spoke and said Graham could only have 20,000 characters in a post.


DarJones   :) :D  :o
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graham d

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Re: Dark matter
« Reply #473 on: April 26, 2012, 04:44:28 pm »
Hello Dar - A couple of years ago I remember doing the forum the courtesy of revisiting Occam's (Ockham) razor as I had not re-read it for nigh on 50 years. Hence, I thought it a good idea to revisit the philosophical musings of a fellow 14th century Brit. I'll be brief- it's utter nonsense. Of course in the formative period of youth it's appealing and science in its early period was infact fairly simple stuff. Would you watch Agatha Christie movies or Homeland or Spooks if the plots were simple; we grow beyond Tooth fairy and Father Xmas tales to the more mature stuff of adulthood.

Current science is anything but simple; it's complex and often multiply counterintuitive. The approach to the Higg's boson was rubbished by the greats you have heard of such as Pauli and Heisenberg when they were my age and older, their proponents theories and themslves were castigated and disillusioned by the old guard. I spent a lot of time in the Earth sciences and life sciences. Scientists are either lumpers or splitters, two ends of a spectrum. Lumpers tend to go for simplicity. In the early development of a scientific discipline, amongst a population of whatever we might classify we look for physical similarities and lump them all together- they all look alike and ignore their disimilarities. As the field developes we start to split.
 
Let me provide an example since you are all astronomers, astrophysicists and cosmologists here, with perhaps a few astrologers too. In the adjacent thread Bruno just reported on new Spitzer data for the Sombrero galaxy. This morning I thought I would check up on its history since after sleeping on it I thought I would check up on a few things, particularly since I had basically rubbished their interpretation of the data.
The Sombrero has a long history of interest to particle particle physicists as well, to do with transverse rotations of the massless goldstone bosons disappearing and reappearing as the Higgs massive boson in the uphill energy oscillation. That's an extreme example of splitters at work awaiting a discovery to this very day.

The Sombrero has a long history and many of you know far more than I have learn about it. Shapley was an astronomer who examined the Sombrero for its content of Cepheid variables to compare I presume with Hubble's gathered data from many other coworkers of whom I know not of. They were chasing a measurement of recessional galactic velocities either through space or what we would now say in space, a stretching or expanding space. He was lumper of course as was Hubble, all Cepheid variables were the same. The age of the universe that was the real problem appeared to be younger than our Earth. When we fast forward you all know now that there are at least two types of Cepheids, and of populations 1 and 2  stars in the halo and disc although you may get stuck remembering I or II types. No doubt there could be more variations and you are now married to splitters. Despite dear old Occam, a sine qua non of lumpers, who was actually interested in the proof of a divinity by pure thought I think we know better these days. It's fact that the bottom line of splitters is we learnt that the universe was twice the age than considered previously.

Cepheid refinement by Baade now made the universe twice as old; unfortunately still wanting at 2 to 3 billion years!.
The key thing about the halo stars is they are much older and redder than the newer much younger bluer stars in the spiral arms or disc where the hidden symmetry of the halo has gone. Had it been different I would be apologising now for my own lame interpretation- and I might still have to. Particle physicists maybe different to astronomers in that they profess that if you throw enough mud at the wall some will stick. That's not a derogatory jibe at all- the physics they do today is difficult and complex and counterintuitive. The route to the Higgs is strewn with blood. Occam saw much of god's blood strewn in the heavens- a single drop nay half a drop would save my soul, time moves on,  bid midnight never come as Faustus saw it. If a theory isn't written in blood what value is it? Dirac's beauty wasn't paid for in blood. U1, SU2 and SU3 is a pig's ear and it appears to look more like a bloody pig's ear if they find Higgsy. I come not to praise Occam but to bury him. He had his day perhaps even in the development of science, but not anymore. Let him rest. Occam RIP.

SN supernovae as standard candles are better and more refined. Time progresses, there are no more lumpers around. Space doesn't appear to just stretch; it's accelerated expansion now and dark energy although the latter is a lumpers concept. Yet even now we are observing new types of SN , amongst the SN's 1 and 1a; not just lumpers initial type 1. I teach you to doubt, doubt everything. You'll get stuck often as you progress through life.

Readabook.One liners are great.Text it,facebook it, twitter it, you always find the simplest explanation;die bona fruere.
« Last Edit: April 26, 2012, 05:31:10 pm by graham d »

paulrogers

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Re: Dark matter
« Reply #474 on: April 26, 2012, 05:57:32 pm »
I thought it a good idea to revisit the philosophical musings of a fellow 14th century Brit. I'll be brief- it's utter nonsense.

Why, Graham, you don't look a day over 80! ::)  You must mean "a 14th century fellow Brit".  :-*

But I take exception to trashing William of Occam.  You overlook the predicate: Given two hypotheses that both equally adequately explain the observation, we should prefer the simpler one.  When we discover new data that demonstrates the two hypotheses are not equally adequate, then we must discount whichever fails.  Occam's Razor was not at fault, it was the lack of demonstrably conflicting data.  There is little or nothing in Science that cannot be challenged by conflicting data, but perhaps the Method itself.

One of my avocations is hybridizing rhododenrons.  In animals the rule is if two types, such as Human "races", can mate and produce indistinguishably fertile offspring, then they're the same species.  But in plants, especially rhodies, it seems the egoistic aim to get your own or your sponsor's name on something for posterity, has led to splitting the genus into hundreds of "species", when in fact there are perhaps no more than half a dozen clades which cannot be intercrossed with impunity.

graham d

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Re: Dark matter
« Reply #475 on: April 26, 2012, 06:54:49 pm »
As more empirical data  is gathered no two hypotheses can equally adequately explain all the data. All things polarise ie. split before they perish.

Thus end members of a species can't interbreed for many reasons. The variants you speak of cannot survive in the wild and will revert to type. Russell Wallace and then Darwin were the first to realise this.

There are 10 species of eucalyptus that can only be recognised biochemically. They look the same to us. However, Koalas eat the leaves from only one species. Find something that eats rhodies and then test them on your rhodies. Occam is dead and turned to clay to stuff your pots and make those rhodies blue.
I don't feel a day older than Occam, Paul.  :)

Bruno

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Re: Dark matter
« Reply #476 on: April 27, 2012, 07:30:27 am »
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sicut hanc, sic et illam fecit Deus, ita ut non inveniat homo quidquam de futuro.
amen
Ciao
Bruno

Cadunt lilia, surgunt rosae
Stellae in caelo sunt radiosae

graham d

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Re: Dark matter
« Reply #477 on: April 27, 2012, 09:17:17 am »
 :)  :) :) That's true Bruno for all of us. None can predict the future. Make the most of it today. Some quantum logicians predict that time doesn't even exist, yet ruinous time claims us all, none escape; viva hodie.

Galaxies may shed a tear, stars and planets are born, evolve and perish. Yet none of us in our fleeting passage in time, should brood or fear, for none are condemned to the pit. Time and time itself is recycled  into the void; nothing escapes its grasp.

graham d

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Re: Dark matter
« Reply #478 on: May 11, 2012, 08:43:18 pm »
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Pluralitas non est ponenda sine neccesitate

Tommaso accepts that Susyiacs cannot be beaten so he lays siege inthe hope that they can be starved to death.

http://www.science20.com/quantum_diaries_survivor/constrained_minimal_supersymmetric_extension_standard_model_written_yet-89947

Lubos like Alirac before him, takes Tommaso, Ockham and Italy to task.
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LM: Well, even if this were an example of Occam's razor, it wouldn't be in conflict with the fact that it is superficially, lousy, and intrinsically unscientific mode of reasoning. Ockham wasn't a scientist; he was a theologian and Franciscan friar in the dark ages, centuries before science was born, so if you are assuming that everything he wrote must be dogmatically viewed as a pillar of science, you should visit your psychiatrist again.
http://en.wikipedia.org/wiki/Alaric_I

Don't knock the Goths, without them Atila wouldn't have got his come-uppance; poor Siegfried.

Read and study Susy MSSM for the approach to Dark Matter. Support the € or we  may go back to the aureas.
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Readers who don't study SUSY at least for 20 hours - after they learned QFT to a reasonable extent -  have no chance to end up with an informed opinion about the state of SUSY.

http://motls.blogspot.co.uk/2012/05/tommaso-dorigo-cmssm-and-demagogy.html
I did mention three years ago that there was no other game in town.




« Last Edit: May 11, 2012, 09:01:51 pm by graham d »

graham d

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Re: Dark matter
« Reply #479 on: May 22, 2012, 10:21:16 am »
Dark Matter Local Density makes a comeback. Or does it?
http://resonaances.blogspot.co.uk/2012/05/dark-matter-is-back.html
Bovy and Tremaine challenge Bodin et al results.
http://arxiv.org/abs/1205.4033
Reonaances quotes
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Currently, the most solid evidence of dark matter comes from  analyzing the Cosmic Microwave Background, and from the observed flatness of the galactic rotation curves. It is less known than in our galaxy the support for dark matter comes from studying the rotation curves at distances of 20 kpc or more from the galactic center. In the immediate neighborhood of the Sun (8 kpc from ground zero), the presence of dark matter is more difficult to deduce. The value of the local dark matter typically quoted, ρ = 0.4 GeV/cm^3, is based on extrapolations using particular models of the dark matter halo. 

A comedy in errors of units has happened.

If you check on www.spaceweather.com  the density of space in the vicinity of the Earth is ca. 1 proton per cubic centimetre( cm3). It varies greatly by a factor tenfold above and below this value. If you like to think that the vacuum of space is nothingness that is empty of all real particles or all particles that can be observed and measured then think of it as that and then add that single proton. Of course you cannot deplete the Sun of just protons and leave the electrons to build up charge, the system as a whole is electrically neutral by the time you reach the heliopause.

Solar mass is a huge mass or 1.989 *1030 kilogram or ~2*1033gram. I am using gram mass measure because they express distance scale in centimeter. 1 gram/cm3 represents density and here on Earth you probably know that is the density of water, a litre of it would represent a kilogram weight. I don't want to get into subleties of why a 1 kg mass  would weigh a sixth of it on the Moon. The shade of the Moon will become a convenient location to track the numerosity of particles in this emptiness of the vacuum.

Astronomers like parsec. 1 parsec pc represents a huge distance the distance covered by light or photons in 3.26 years. That's about the distance to the nearest star and compare it with the ca. 8 minutes of light time travel from Sun to Earth.
 
1 pc is equivalent to 3.0857*1016metre ~3.1*1018cm. A cubic parsec is a volume 2.94*1055cubic centimetre

You are asked to consider this thought experiment. The Sun is essentially hydrogen atoms, ignore a correction for helium and other trace elements. Disociate the Sun, this 1033gram of H atoms, and spread it evenly throughout this parsec volume of 1055cm3 to give a uniform density that is tiny ~6.77 *10-23gram/cm3

Rather than expressing units of mass in gram the particle physicists like massenergy terms such giga electron volts. A proton has a total mass energy content of 938 million electron volt (eV) or 0.938GeV or ~1 GeV.
1 gram of Hydrogen is essentially 1 proton plus one electron, multiplied by an enormous number, with the latter mass only ca. 1 two thousandth that of the proton. We can ignore its contribution until we go to the shade of the Moon locality.

1 gram of protons (essentially H) contains an Avergadro number of particles ( 6.022 * 1023 particles). So the act of dispersing all those solar H or essentially protons through 1 cubic parsec, expressed as cm3, gives a particle proton numerosity of 40.9 particles per cubic centimetre. This has a mass energy content of ~ 40 GeV/cm3. This density compares with the spaceweather value of~1 particle or proton equivalent ~1 GeV in the Earth vicinity. The anticipated dark matter fraction 0.008 in our galactic neighbourhood represents 0.32 3GeV per cm3. So the unit conversions appear correct, say to within 10% accuracy.

1 particle or proton equivalent per cm3 represents 1 million proton per cubic metre space. Let us compare this with Weinberg's old calculation that puts the critical density of the universe as ca. just under 3 particles per cubic metre, based upon old Hubble data, now revised. The modern value is between ca. 4 to 6 particles as proton equivalents(H) per cubic metre space (~4 to 6 GeV/m3).
Most folk now know that the dark matter DM fraction is say 25% of the whole and that the normal matter fraction is at best 5% of this critical density. Of the 4 to 6 particles/ m3 universal space then there is about 1 DM massenergy equivalent GeV/ m3space.

Weinberg uses the mole concept since he is using the Avergadro unit and expresses particle densities per litre (1000 cm3of space.
What is a mole? Lubos hates it and the so called Avergadro constant. Chemists like to dissolve a mole of substance or substrate into water and bring it up to 1 litre in volume of water. It's very simple but can take time, so the concept changed to just bung in the solid particles into exactly 1 litre of water and call it molal! For our purposes the difference is negligable.

As an illustration let us dissolve 1 gram mass of H atoms (the H in a cylinder is actually the diatomic H2 into water. 1 gram H contains 6.022*1022 particles (H atoms; forget the quarks etc). The concentration represents 1 mole/litre water. The atom mass of H is 1 (or almost so). For fizzy water you could dissolve carbon dioxide CO2 to make up a 1 molar solution. In this case the atom masses for C is 12 and for O it is 16. Hence you would have to dissolve 12 gram plus twofold 16gram or 44 gram of CO2 molecules to obtain a 1 molar solution of fizzy water. Were you to achieve it, it would be pretty explosive cava. Yet 1 molar solution still contains that same number of particles(CO2) or Avergadro's number. Water, molecular water is H2O molecular mass 18. What is the concentration or density of watr in water? This is a hurdle for many. Well a litre of water weighs (really mass) is 1000gram. So the concentration of water in water is 1000gram/18gram or 55.6 moles per litre. How many particles of water are there in 1 litre of water? Simply 55.6 fold Avergadro's number.

 Weinberg uses  empirical results done in today's laboratory to determine photon numerosity in black body radiation and to extrapolate it back to energy densities in the early universe. He conserves the number of photons as they are compressed back to higher frequencies. The converse is universal expansion where the photons since recombination are conserved numerically (ie. they don't thermalise with normal matter) but their frequencies are lowered by the size fraction increase.
 
If we go to the dark side of the moon in orbit, shaded from the trillions of  2-10 eV solar photons minus those 1GeV per cm3 solar protons we are in a vacuum. Here on Earth the only place you will find such a high vacuum is in the beam pipe of the LHC. Relativistic protons will also collide with stray air atoms and neutrons. High vacuum and ultra low temperatures are needed, almost like the far side of the moon.
What is the concentration of the vacuum in the vacuum? Uh! This is a hurdle but you appreciate what the molar concentration of water in water is.

 On the far side of the Moon you are sheltered from solar photons if you keep pace with the orbits around the Sun and Earth. OK there are copious cosmic ray particles and starlight photons. In addition, there are those CMB photons which Weinberg regarded as 1billion to 10 billion more numerous than every proton equivalent particle you encounter. How many? About the order of 10 million photons per cubic metre space, average energy 0.000233 eV per Kelvin from those laboratory experiments. In addition, there are high energy neutrinos from the sun. It takes a couple of million eV energy to ecape the nucleus as a H atom changes to a neutron in the solar core. Every second of the order of a trillion pass through the Moon or Earth per square metre, so the shaded position behind the Moon. The neutrinos don't interact that often so that they are changed to charged leptons but they are refracted or lensed to some point of focus in the outer solar system. It's difficult to find a sheltered spot where the vacuum is zeroed ie. has zero energy. The anticipated CMB neutrinos as abundant as CMB photons are present as well, everywhere infact. Finally what about dark energy. As a predicted 75% fraction of the critical density this also additionally represent three quarters of those ca. 5 particles(as proton 1GeV equivalents) or let's say 4 particles, leaving only 1 particle (as normal matter and DM combined) per cubic metre of space present day.

In the Weinberg model each one of these photons and each neutrino, that is for each one you observe for every cubic metre of the present universe, once had enormous kinetic energy, enough not only to seed a proton mass energy, but in the inflation model to seed something far more incredulous, not even a whole star's mass energy but a whole galaxy or more. Weinberg left it at a more comprehensible level, about a parsec of distance and density of about 1 billion fold water density or fold 55 molar.

The CMB density of the cosmos is uniform at about 0.5 of an electron mass per cubic metre space from the astronomical implications thread. An electron particle has an energy that is 511,000 eV or half a milion eV when compared with the ~1000 million eV proton(~1GeV). This ~255,000eV represents the concentration of the vacuum in the vacuum present day. It's about 1 four thousandths of the GeV of the proton equivalent. There's no place for a DE component, only for normal and for dark matter. Even in the shade of the Moon or anywhere else it impossible to escape the residual density of the vacuum, ca. order 10 million low energy photons and neutrinos/per metre cube of vacuum. Infact, from such a low energy start of a spacious vacuum that all the NM and DM that we now observe evolved.

That remains speculative ofcourse until we obtain absolute masses of neutrinos. Yet we are close. It's not too long a wait. Historically, electron colliders discovered particle pair annihilations in the range up pion masses, then proton masses, three orders of ehanced mass energy collisions. The Lep collisions established mass energy by a further two orders of energy magnitude and now the LHC collider extends well beyond 100 GeV energies, or two orders of magnitude enhancement. Currently the cumulative rest mass energies of the neutrinos is at 0.5eV. That is only one order of magnitude to bridge by comparison. Infact, it is now so small that someone might predict that we would expect to see a residual continuum noise of photon neutrino production and annihilation from the vacuum energy of the cosmos, representing  the concentration of the vacuum in the vacuum.




« Last Edit: May 22, 2012, 11:09:57 am by graham d »