Posted: Jan 24, 2015 2:37 pm
by Calilasseia
Answering a couple of points here ...

[1] This one ...

Macdoc wrote:Carl ....tune an old fashioned TV between stations and WATCH ....."ancient history".....that hiss and static IS the remnants of the big can look and listen to.

This is science....your premises are ignorance writ large...

Go back to kindergarten and get some education in science instead of making a thorough fool of yourself on a rational based board. :nono:

I'm reminded at this juncture of the famous XKCD cartoon ...


Oh wait, that graph I've just illustrated? The correlation is so precise, that the error bars are too small to draw on the graph. This is how precisely the curve for Planck's Law matches the cosmic microwave background. From the Wikipedia page devoted to the CMB, we have this:

The high degree of uniformity throughout the observable universe and its faint but measured anisotropy lend strong support for the Big Bang model in general and the ΛCDM ("Lambda Cold Dark Matter") model in particular.

That model, the ΛCDM model, has made the following successful predictions:

[1] The existence of baryon acoustic oscillation. To understand what this is, remember that the CMB, whilst being highly uniform, does contain measurable anisotropies, corresponding to differences in density in the early universe. In short, some regions contained slightly more matter than others. The denser regions, courtesy of gravity, attracted still more matter to them. However, as is observed to be the case during star formation, that attraction of matter results in the temperature of the dense attracting regions increasing, in accordance with the Gas Laws (this phenomenon is observed on a smaller scale when you inflate a bicycle tyre - increase the internal pressure, and you increase the temperature). Some of that matter, as a result of increasing temperature, acquires a radial outward motion. However, note that the ΛCDM model covers two distinct types of matter: standard baryonic matter, which interacts with the electromagnetic force, and cold dark matter, which only interacts via the gravitational force. The baryonic matter is the matter that experiences a counter-force to gravity, but the cold dark matter does not. The cold dark matter remains at the centre of the dense regions, providing a continued gravitational force attracting the baryonic matter back.

Now what happens, is that photons associated with the baryonic matter, decouple from that matter, and in doing so, radiate away the heat energy to the surroundings, and allow the temperature to fall again. This results in lower velocities for the baryonic matter, and consequently, that baryonic matter is attracted back again. This oscillation is what is known as baryon acoustic oscillation, and the ΛCDM model was the first model to predict the existence of this phenomenon in the early universe. This mechanism eventually has an effect upon the distribution of galaxies much later in the history of the universe - it results in galaxies being clustered at a specific scale. By analysing the observed distribution of galaxies, and observing clustering at the requisite scale, baryon acoustic oscillation can be searched for in that distribution. The ΛCDM model predicted the existence of the phenomenon, and the clustering scale that it would generate later in the history of the universe. The CMB, incidentally, provides additional information about baryon acoustic oscillation to high accuracy, allowing an additional check to be made.

[2] The polarisation of the CMB. Photons of light have a polarisation associated with them, and the ΛCDM model predicted that the observed polarisation of the CMB would consist of two classes, known as E-mode and B-mode polarisation. If the electric field associated with a photon is E, and the magnetic field associated with the same photon is B, then E-mode polarisation arises as a consequence of the fact that the curl of the electric field is zero. B-mode polarisation arises as a consequence of the fact that the divergence of the magnetic field is zero. E-mode polarisation values arise naturally as a result of Thomson scattering in the requisite plasma, and the signal for E-mode polarisation is strong as a consequence. B-mode polarisation, on the other hand, has a much weaker signal, some of which is interfered with by the E-mode signal, so determining the precise level of the B-mode signal, and the nature thereof, is a difficult task, involving some fairly intricate apparatus, followed by a lot of hard mathematical work with deconvolution.

However, the fun part is this: the B-mode signal can arise from two sources. The first source consists of gravitational lensing of E-mode signals. This effect has already been measured. The second source consists of perturbations in space-time arising from gravitational waves generated by cosmic inflation. As a result of this second mechanism, the precise nature of the B-mode signal, once properly deconvoluted from the E-mode signal, provides an empirical test of the likely validity of cosmological theories. In short, any cosmological theory that predicts a specific spectrum of values for the gravitational wave B-mode signal component, falls by the wayside the moment a different spectrum of values is measured. Since B-mode polarisation spectra arise from all the mechanisms invoked by modern cosmological theories, the observed B-mode spectrum provides an empirical test, allowing us to rule out those theories predicting a spectrum significantly divergent from the observed spectrum. At the moment, the difficulties lie in deconvoluting the B-mode signal in a manner allowing the precise spectrum to be determined, but work is underway to address these issues.

[3] The statistics of weak gravitational lensing. Gravitational lensing was, of course, one of the famous predictions of Einstein's theory of general relativity, that were found to be in accord with observational data to a striking degree of precision. Although other workers alighted upon the concept before Einstein, Einstein was the first to provide a quantitative analysis of the phenomenon, in a well-known 1936 paper.

However, gravitational lenses behave differently from optical lenses, and these differences in behaviour allow a range of other phenomena to be tested. Strong lensing was tested for with relative ease, courtesy of the fact that a strong gravitational lensing source produces large and easily detectable distortions in the receieved image of an object behind that source, relative to our viewpoint. The so-called "Einstein ring" has been observed being generated by many different sources. Weak lensing, on the other hand, requires more work to analyse, as it involves detecting the much smaller distortions arising from a multiplicity of much less powerful lensing sources. However, once this hard work is completed, the data allows us to determine, with precision, the mass distribution in the lensing region. Which again has cosmological implications. A cosmological theory that fails to reproduce the correct mass distribution is again sent back to the drawing board.

Now, whilst there exist certain systematic sources of measurement error to be overcome, these sources are known, and can be counteracted, though this process tends to be expensive, and involves using space-based observational tools. However, data has now been gathered, and as a corollary of that data gathering, the ΛCDM model has once again acquitted itself, by providing the best account for observed weak gravitational lensing statistics. It provides the best fit with respect to predictions of matter distribution in weak lensing regions.

So when Carl posts yet more apologetic fabrications about "speculation", you can read the above and toss his drivel into the bin where it belongs. :)

Next ...

redwhine wrote:
Calilasseia wrote:Most scientists I know are running ten year old second hand cars, not private jets, with the exception of those fortunate few who have picked up their Nobel Prizes.

"Illustrious", perhaps? (I get your meaning but "fortunate" makes it sound like they simply bought a winning lottery ticket or something. Years of hard work =/= fortunate.)

An admittedly unfortunate choice of adjective in the heat of the moment, as you have revealed above, but I am minded to note that a lot of extremely high standard work, on the part of some extremely eminent people, never sees that shiny medal. It's a measure of how much high standard work our scientists produce, that only the most resolutely ground-breaking work even gets a look in. The problem with the Nobel Prize, is that it's partly a victim of its own success: having established itself as the most prestigious award in science, the constraints upon consideration of likely candidates are extremely tight. For example, Stanley Prusiner received his Nobel Prize, because he established evidential support for an idea so revolutionary, that it took quite a few biologists by surprise when he finally delivered that evidence. The idea that nucleic acids were not the only self-replicating molecules possible was such a shock to many, that when Prusiner not only discovered the existence of alternative replicators, but demonstrated conclusively that they were central to several important disease processes, that his work well and truly fell into the "ground breaking" category.

With respect to the above exposition I've provided on the ΛCDM model, which is our best current model of observed spacetime, if a physicist were to alight upon data telling us that said model had actually got it wrong, and provided a better model to go with the data, said physicist would be a natural candidate for a Nobel. This is the standard of work required now, and it's in that sense, that I describe the recipients as "fortunate", because they've managed to move to the front of the queue by dint of their work being truly exceptional. I never intended to detract from the fact that they made that good fortune through monumental labour, a point I've repeatedly stressed in many past posts, and as a consequence, regarded the requisite exposition as superfluous to requirements to those familiar with my output here. :)