Da big bang

**PBI** · 08-04-2008, 14:12

Rebuttal 2) I think the key words in your statement was, ‘each scattering event introduces a random change in its direction.’ I don’t think I said that the changes in direction were scattered or random, rather that they were specific. As it pertains to a colour shift, of course we talking about either a lengthening of the wave or a change in resonance. The usage is Compton Scattering or Compton Effect, not Comption scattered as technically, the effect is not defined by random scattering.

Forgive me if I misunderstand you, but by Compton scattering, I understand you to refer to the process whereby an electron absorbs a photon, and then re-emits a photon of a longer wavelength. If this is the mechanism by which the redshift is introduced then since it is a quantum mechanical process the direction in which the photon is re-emitted is inherently random.

A second problem arises if we take a look at the Compton scattering equation:

(initial wavelength) - (final wavelength) = (constant) * (1-cos(D))

Where D is the angle by which the photon is deflected from its original direction of motion. Thus, while a few photons will continue on their original heading and not be deflected, if we set the angle D to be zero for such a case it is clear that in this case that the initial and final wavelengths will be identical, thus they will not be redshifted.

So this is the problem I have with the idea of Compton scattering causing galactic redshift. Firstly, the deflection of the light in addition to the lengthening of its wavelength should mean that at best galaxies should appear as fuzzy blobs rather than clearly defined objects, and improving the telescope resolution will not reveal any further detail. At worst, the scattering of photons will be so severe that distant objects will not be visible at all since the scattering will be so severe that the interstellar medium would be effectively opaque.

Secondly, any light which travels directly to us in a straight line will not be redshifted at all no matter how many electrons it scatters off. Thus, we have two clear predictions from a theory of redshift caused by Compton scattering: Smearing of images of galaxies which will not be improved by improving the telescope, and light from the center of the image should not be redshifted at all. Neither of these is observed, which to me seems to be a severe flaw in such a theory.

Question 1) how come the light from such sources all arrives at the Earth coming from the same direction?

Answer 1) I don’t believe the evidence actually indicates that galactic light approaches our system from the one direction. If so that would mean that galactic structures within one or more visual vectors would demonstrate the redshift, while in one or more vectors the blueshift would be evident. The way I understand the evidence, is that all distant galactic structure are marked by the redshift, and all near structures are marked by the blueshift, regardless of the visual vector. For example, we have the Triangulum and Andromeda Galaxies and many other blueshifters. Please see the vectored view of the Local Group (LG) provided below, as you will note that distance and not visual vectoring is the qualifying factor for redshift vs blueshift. Also note this view is relatively flat, so those features that appear near the center bottom of the graphic, are referenced with doted lines to plot there location, and are not below the horizon of the LG.

Actually, I was simply referring to the light from a single galaxy all arriving from the same direction rather than coming from many directions in space which is what I would expect if the light is being repeatedly scattered. As I mentioned above, the image should be smeared out, rather like a light seen through thick fog.

**cmacq** · 08-05-2008, 00:06

Poor Bloody Infantry

I’m a bit tied up right now, but give me a few days to respond to your question.

CmacQ

**PBI** · 08-05-2008, 12:01

Please take all the time you need.

Speaking of which, I should probably get back to work too, since interesting as this discussion is, it's not going to get my thesis written.

**cmacq** · 08-05-2008, 13:47

The Master's...

by the way, your thesis is?

**cmacq** · 08-06-2008, 06:26

Part I
Directly, the answer to your question was from a pervious post, found in the following sentence, however I’ll admit it was rather laconic and vague.

‘Remember everything within the graphic is in motion and this is relative, not scattered nor random.’

As a reference, this may sound a bit obtuse, but please bear with me, as this provides the rationale for my answer. Previously I posted that the way the Copernican Principle has recently been employed, i.e. the earth is as good as any other place to observe the universe, is utter rubbish. I maintain that the earth is actually a horrific place (but not the worst) to view the universe, as there are available far better points from which to surveil.

The reasons are as follow. First, in theory our planet lays within the Terran star system, wherein we have a single G2 class base star, several planets; several dwarf planets, numerous moons, billions of smaller bodies, debris, dust, solar winds, the Interplanetary Medium, and the Oort Cloud. All of these exist within a horizontal plane, which is tilted at a particular angle in relation to our galaxy, and is in relative motion around the base star, our sun. Although collectively, these motions are not uniform, yet neither are they random, as there is an interdependence, however dominated by the base star.

Next our Terran star system is in motion within a Local Interstellar Cloud, known as the Local Fluff. This is an outflow from the Sco-Cen, and is roughly 30 light years across. This gas cloud has a temperature of 6000° C, which is about the same surface temperature of the Sun. Overall, it’s very dispersed, with a density of 0.26 atoms per cm3. Interestingly the Local Fluff is in motion in relation to the Sco-Cen. Again this motion is not random.

Our system along with the Local Fluff and other fellow travelers are in motion within the Local Bubble. This is a cavity in the interstellar medium, which I’ll get to next. It’s about 300 light years from one side to another and has a neutral hydrogen density of approximately 0.05 atoms per cm3. This diffused gas is hot and somehow emits X-rays. This in part is likely due to the Local Bubble being the remains of a supernovae that exploded between two to four million years ago.

Next our system, the Local Fluff, and the Local Bubble are in motion within the interstellar medium which is in turn associated with the Orion Arm. The interstellar medium (ISM) is another gaseous formation that surrounds the stars that compose the greater structure of our Milky Way Galaxy. Its density is about 0.5 atoms per cm3. Overall the ISM within the Orion Arm (OA) is very big and as one of several minor arms, the OA is in motion between the Sagittarius and the Perseus arms, two of the four major arms of the our galaxy. All these are in relative motion, which is dominated by the center of our galaxy. Although so complex they're beyond our current understanding, none of these motions can be classified as random.

Beyond this, along the plane of the intergalactic horizon is intergalactic space which, as provided above, has a theoretical average density of around one hydrogen atom per 1 m3. This expanse is in motion as is the Local Group, seen in the graphic above, as are the seemingly numberless other groups of galaxies found further afield. Again, all these are in motion and these motions are all relative.

The point and the answer to question to follow.

CmacQ

**PBI** · 08-09-2008, 00:28

Since you ask, I am studying for a PhD in Theoretical Physics. The research we do is all about finding new techniques for performing scattering calculations to provide predictions for experiments such as those at the LHC (although that makes my work sound altogether more grand than it actually is); hence why I know a thing or two about Quantum Mechanics and Compton scattering (though of course, I certainly wouldn't claim to know everything there is to know about either of those topics).

Spoiler Alert, click show to read:

To be precise, what we do is to work on alternative methods for finding scattering amplitudes in Quantum Field Theories, since the Feynman diagram techniques currently used become wildly inefficient for interactions involving large numbers of particles. To crank the jargon up a notch, we specifically use Unitarity-based methods which allow complicated loop integrals to be reduced to products of tree amplitudes multiplied by a known integral basis.

The other interesting strand of our research revolves around the study of N=8 Supersymmetric Quantum Gravity. As you may know, most quantum theories of gravity suffer problems with infinite terms appearing in calculations which are impossible to cancel. One possible way around this is to treat particles as extended objects, known as String Theory; however, this approach is fraught with its own set of problems (as well as being an utter nightmare to calculate anything in). The hope of N=8 SUGRA is that due to large cancellations in such a heavily supersymmetric theory the infinite terms will not appear, allowing for the possibility of a Quantum theory of gravity without introducing all the problems of String Theory.

So far, no divergent terms have been found in any of the N=8 amplitudes calculated. In fact, the cancellation between terms appears to be a good deal stronger than expected from the degree of Supersymmetry. This is interesting because this additional cancellation is quite distinct from the Supersymmetric contribution, and the mechanism behind it is AFAIK pretty much a mystery. Obviously, as more N=8 amplitudes are explicitly calculated, the picture will become clearer, which is where we come in with our unitarity methods.

The problem, of course, is that even if N=8 SUGRA turns out to be finite in four dimensions, nature is simply not N=8 supersymmetric. Therefore, the best we can ever hope for with N=8 is that it could act as a proof-of-concept that a sensible quantum field theory of gravity can exist (albeit not in this universe), and also hopefully as a context in which to study this mysterious new cancellation. The longer term picture depends largely on whether extensions of the theory can be found which look anything like the real universe; my supervisor once described it something along these lines:
The question is whether N=8 SUGRA will turn out to be Rockall, an isolated, barren patch of rationality in a vast sea of divergence; or whether it will be Tahiti, a single island in a vast chain of rich and diverse islands (not to mention a more appealing holiday destination than Rockall).

Of course, if you managed to follow any of what I just wrote, you're doing better than I am!