What caused the tiny variations in the Cosmic Microwave Background?

[Buckethead]

Understand that accelerating and expanding are two different concepts. We've known the universe is expanding ever since Hubble, and the logical conclusion is a very dense early universe. The acceleration only comes into increase the rate of expansion a bit -- the conclusion is not changed, just (I suppose) the timeframe.

Here's an excellent http://en.citizendium.org/images/thumb/c/cc/Universe_expansion_graph_with_Omega_values990350b.jpg/350px-Universe_expansion_graph_with_Omega_values990350b.jpg" which hopefully should show you what I mean. The dark red represents the universe with acceleration, whereas the green and blue lines are closer to how we thought the universe was prior to the discovery of the acceleration.

When we used just expansion then this easily projects backward to 0,0. But when you add acceleration and if acceleration were a constant, then the red line on the graph would actually end up at 0, y where y is > 0. On the graph the red line curves down toward 0,0 but this would imply acceleration was not a factor in the earliest universe.

 

[Nabeshin]

On the graph the red line curves down toward 0,0 but this would imply acceleration was not a factor in the earliest universe.

Indeed! The expansive power of dark energy does not scale with the volume of the universe. So in the beginning, effects due to matter and radiation were much larger and it could be effectively ignored. Until some time a few billion years later at which point the terms due to radiation and matter become comparable to the dark energy term, and we "see" the expansive parameter (red graph begins to be concave up).

If you don't believe the graphs, just solve the Friedmann equations for yourself and see.

 

[Buckethead]

Indeed! The expansive power of dark energy does not scale with the volume of the universe. So in the beginning, effects due to matter and radiation were much larger and it could be effectively ignored. Until some time a few billion years later at which point the terms due to radiation and matter become comparable to the dark energy term, and we "see" the expansive parameter (red graph begins to be concave up).

If you don't believe the graphs, just solve the Friedmann equations for yourself and see.

How far back on that graph have we been able to see by observation (as far as measuring the change in acceleration)? It looks as if the red line ends at about 400K years, which I know is about how far back we've looked in time, but how far back have we actually been able to measure the change in acceleration? If we've only gone back perhaps 12 billion years ago, then on the graph this is just about where the red line starts to curve down. If we projected it as a straight line from this point it would intersect the y-axis at about 1/40 the current size of the universe. Is this large enough for the acceleration to kick in?

In other words, do we have observational evidence that the red line actually did curve downward further back than 12 billion years ago, or at least good mathematical proof that this was the case? Is it possible (although I realize not at all accepted) that the universe could have formed at .1 it's current size and began to accelerate from there or was the influence of the matter and radiation at that time still way too large for this to be the case?

 

[Ich]

In other words, do we have observational evidence that the red line actually did curve downward further back than 12 billion years ago, or at least good mathematical proof that this was the case?

The most convincing data from the earliest epoch is baryogenesis. That gives some good constraints on how fast the expansion has been back then. It was faster, so the red line curved downwards.

Is it possible (although I realize not at all accepted) that the universe could have formed at .1 it's current size

With a CMB of redshift 1089, that's not an option.

 

[Buckethead]

The most convincing data from the earliest epoch is baryogenesis. That gives some good constraints on how fast the expansion has been back then. It was faster, so the red line curved downwards.

With a CMB of redshift 1089, that's not an option.

With regard to baryogenesis, is it at all possible that baryons could appear from virtual space without also generating anti-baryons, or is this simply an impossibility?

With regard to the redshift of CMB, I recall reading there are some skeptics that question the accuracy of the distance/speed of the CMB calculated from the redshift, but also read it didn't hold much weight.

Thanks for the answers.

 

[Ich]

With regard to baryogenesis, is it at all possible that baryons could appear from virtual space without also generating anti-baryons, or is this simply an impossibility?

Don't know what you mean by "virtual space", but obviously there are more baryons than anti-baryons. The mechanism is not well understood. However, there has been http://www.physorg.com/news193403945.html" recently.

With regard to the redshift of CMB, I recall reading there are some skeptics that question the accuracy of the distance/speed of the CMB calculated from the redshift, but also read it didn't hold much weight.

No, that's quite established in mainstream physics. If you're interested, http://www.astro.ucla.edu/~wright/stdystat.htm" 's a diatribe on such fringe claims. The whole website is worth reading.

 

[Chronos]

There are also those who contend the surface of the sun is composed of iron. These arguments also do not hold water [or iron]. Science is built upon pillars of sound observational evidence. A few termites are unlikely to undermine that foundation. We do, however, still have much to learn. Some of the 'truths we hold near and dear today will eventually be replaced by better models. But, that is how science works. Show me the money, as they say in the hallowed halls of academia.

 

[ViewsofMars]

Don't know what you mean by "virtual space", but obviously there are more baryons than anti-baryons. The mechanism is not well understood. However, there has been http://www.physorg.com/news193403945.html" recently.

Thanks Ich. Here is the entire publication that pertains to your link from physorg.com. It does discuss baryons as well:

Fermilab-Pub-10/114-E
May 16, 2010
Evidence for an anomalous like-sign dimuon charge asymmetry
http://arxiv.org/PS_cache/arxiv/pdf/1005/1005.2757v1.pdf

Also, the European Space Agency has a wonderful website that discusses the Big Bang Theory. Here is a snippet from that page.

Low-energy clues to a high-energy puzzle
The CMB pervades every direction in the sky with almost the same brightness. But measurements of its apparent temperature have revealed that tiny differences do exist — as tiny as one part in a million.

The tiny variations hold clues to profound puzzles, they are actually imprints left behind by matter in the past.

At the beginning of the Universe’s life, temperatures were still very high: three minutes after its birth, the temperature was about 1 thousand million degrees K. Under these conditions, matter was ionised and tightly coupled to radiation, i.e. light could not travel freely. By studying the energy distribution of the photons at this early time, we can learn what the properties of matter were back then.

Slowly, as the universe expanded and cooled to below 10 000K, the ions began to recombine—this event is known as ‘recombination’. Recombination was complete about 380 000 after the Big Bang, when the Universe cooled to 3000K, and light was able to travel freely.

Most primordial matter is comprised of neutral hydrogen gas. It is transparent, so most of the light originating from this early period of the Universe’s history is able to reach us in its almost original state.

With the expansion of the Universe, the wavelength of the light emitted (CMB) has increased, and as a consequence the temperature of the CMB has changed from its original 3000K to 2.7K as is observed today. The ratio by which the wavelength has increased tells us about the factor by which the Universe has expanded since the time the photons were emitted.
http://www.esa.int/SPECIALS/Planck/SEM1R20YUFF_0.html#subhead2