Cosmology Notes/draft - Revision history

Johnno: /* What is wrong with cosmology? */

2011-10-16T07:54:15Z

What is wrong with cosmology?

Johnno: /* Cosmic Microwave Background Radiation (CMBR) */

2011-09-29T22:46:35Z

Cosmic Microwave Background Radiation (CMBR)

Johnno: /* Inflation */

2011-09-29T22:27:49Z

Inflation

Johnno: /* Dark materials */

2011-09-29T22:21:08Z

Dark materials

Johnno: /* General Relativity */

2011-09-29T22:16:00Z

General Relativity

Johnno: /* What is wrong with cosmology? */

2011-09-29T22:14:33Z

What is wrong with cosmology?

Johnno: /* What is wrong with cosmology? */

2011-09-29T22:06:48Z

What is wrong with cosmology?

Johnno: /* What is wrong with cosmology? */

2011-09-29T22:05:45Z

What is wrong with cosmology?

Johnno: /* General Relativity */

2011-09-29T04:39:05Z

General Relativity

Johnno at 04:23, 29 September 2011

2011-09-29T04:23:22Z

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 # the ''"Cosmological Principle"'' - the postulate that the Universe is both ''isotropic'' (the same in all directions) and ''homogeneous'' (matter distribution is "smooth" on a sufficiently large scale),
 # that the ''Cosmic Microwave Background Radiation'' (CMBR) is the afterglow from the Big Bang,
-# that the ''Hubble relation'', the highly isotropic relation between a galaxy's redshift and its brightness (and therefore roughly, its distance) and its redshift, shows that the Universe is expanding, and
+# that the ''Hubble relation'', the highly isotropic relation between a galaxy's redshift and its brightness (and therefore roughly, its distance) shows that the Universe is expanding, and
 # that the abundance of primordial elements (the amount of H, He, and Li in the Universe) can be calculated from the model to match observations.

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 === Cosmic Microwave Background Radiation (CMBR) ===
-An extremely isotropic near-perfect black body microwave radiation, with a temperature of about 2.7 Kelvin. Supposedly the afterglow from the Big Bang. Mapped by the Wilkinson Microwave Anisotropy Probe (WMAP).
+A near-perfect black body microwave background radiation with a temperature of about 2.7 Kelvin, originating from all points in the sky (isotropic). Detected by radio astronomers in the 1960s, and interpreted as the afterglow from the Big Bang. Measured in 1990 by the COBE satellite and more recently by the Wilkinson Microwave Anisotropy Probe (WMAP). According to the Big Bang model, anisotropies (small variations from the black-body curve) are evidence of the "clumpiness" (inhomogeneity) present at the very beginning of the Universe which lead directly to the large-scale structures we see today.
-There is evidence that the CMBR is nothing to do with the afterglow of the Big Bang. It could be simply the ambient temperature of space. Starlight radiating in a Universe with its observed matter density produces a black-body radiation of about 2.5 Kelvin. Plasma filaments re-radiate light as microwaves and produce a radio fog, so the CMBR could be anything but background, produced instead within the nearest few thousand light years and thus local to our own part of the Milky Way. Fog is very good at making any light sources, such as headlights and the Sun, extremely isotropic.
+There is evidence that the CMBR is nothing to do with the afterglow of the Big Bang. It could be simply the ambient temperature of space. Starlight radiating in a vacuum would produce a black-body radiation of about the same temperature, given the Universe's observed matter density. Plasma filaments are very efficient at absorbing radiation and re-scattering it as heat and microwaves. Given their distribution just within our part of the Milky Way, they would very quickly produce a radio "fog", which to radio telescopes would look exactly like the CMBR. This would make it a local, not a cosmic, background radiation.

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 === Inflation ===
-Cosmic inflation was a mechanism thrown in to explain the presence of very large scale galaxy clustering in the current Universe, given its supposedly isotropic and extremely homogeneous initial state and only 14 billion years in which to form such large structures. Sadly, it replaces that observational problem with imaginary physics which can create matter from nothing, expand it at faster-than-light speeds, and suddenly slam the brakes on and dump particles at an arbitrary point in time. Despite this, cosmologists point to the WMAP probe and the supreme isotropy and homogeneity of the CMBR as confirmation that inflation must be true, despite the completely contradictory extreme in-homogeneity of galactic super-clusters and the vast voids between them, and the fractal distribution they represent.
+Cosmic inflation was a mechanism thrown in to explain the presence of very large scale galaxy clustering in the current Universe, given its supposedly isotropic and extremely homogeneous initial state (as indicated by CMBR data) and only 14 billion years in which to form such large structures. Sadly, inflation theory replaces that observational problem with completely unknown and imaginary physics, which (luckily for our prevailing model) can create matter from nothing, expand it at faster-than-light speeds, and suddenly slam the brakes on and dump particles once the energy density has dropped below a certain threshold, at which point "normal" physics pops into existence. Despite this, cosmologists point to the WMAP probe and the supreme isotropy and homogeneity of the CMBR as confirmation that inflation must be true, in the face of the contradictory extreme fractal inhomogeneity of galactic super-clusters and the vast voids between them.
 === Cosmic Microwave Background Radiation (CMBR) ===

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 === Dark materials ===
-Given the observed expansion rate, the observed matter distribution is far from sufficient to produce a required Ω value close to one; matter alone only adds up to about 0.04 which doesn't fit. Scientists then postulated dark matter to make up the difference, even though they still to this day do not know what it is. In the 1990s, observations of supernovæ purportedly showed that the rate of expansion has been slowly increasing over time, which requires a dark energy field to make things fit. So now we have Ω consisting of 4% matter, 23% dark matter, and 73% dark energy. All attempts so far to directly measure or quantify either dark matter or dark energy have failed.
+The observed rate of expansion of the Universe requires a Ω value very close to one, but the observed matter distribution only produces a value of about 0.04, which is far from sufficient. Scientists then postulated dark matter to make up the difference, even though they still to this day do not know what it is. In the 1990s, observations of supernovæ purportedly showed that the rate of expansion has been slowly increasing over time, which requires a dark energy field to make things fit. So now we have Ω consisting of 4% matter, 23% dark matter, and 73% dark energy. All attempts so far to directly detect, measure or quantify either dark matter or dark energy have failed. Could it be that the model is wrong, and that it simply isn't there to observe?
 All that is pointless anyway since we now know (from recent SDSS, Hubble, and later galaxy survey data) that matter is distributed fractally with dimension D=2 even at the largest observable scale, so the assumption that matter is distributed homogeneously is false, which means Ω is meaningless, which invalidates modelling the Universe with a FLRW metric. Curiously, by definition this fractal distribution of matter has an average density that tends to zero over ever increasing scales, rendering Ω even more pointless as a meaningful measurement.

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 == General Relativity ==
-The current model is based on a particular mathematical solution (called the ''Friedman-Lemaître-Robertson-Walker metric'', or FLRW for short) of Einstein's field equations in his theory of General Relativity. General Relativity describes the Universe in terms of masses interacting with and distorting ''spacetime'', a four dimensional mathematical space (a ''Riemannian manifold'') which has the three dimensions of normal ''"Euclidean"'' space, plus one of time. One of the results of considering the Universe in this way is that gravity becomes no more than the linear trajectories of the moving masses in this four dimensional space, rather than a separate, arbitrary force that needs to be separately considered.
+The current model is based on a particular mathematical solution (called the ''Friedman-Lemaître-Robertson-Walker metric'', or FLRW for short) of Einstein's field equations in his theory of General Relativity. General Relativity describes the Universe in terms of masses interacting with and distorting ''spacetime'', a four dimensional mathematical space (a ''Riemannian manifold'') which has the three dimensions of normal ''"Euclidean"'' space, plus one of time. One of the results of considering the Universe in this way is that gravity becomes no more than the linear trajectories of the moving masses in this four dimensional space, rather than an arbitrary force that needs to be separately considered.
 This model has a parameter Ω representing average density - assuming the matter distribution of the Universe is homogeneous - that determines the overall ''curvature'' of spacetime. If the parameter is exactly one, then spacetime is "flat", equivalent to normal Euclidean space. If not, then spacetime is curved, leading to expansion or contraction, either bounded or unbounded depending on whether Ω is smaller or greater than one. This model was formulated in the 1920s, so when Edwin Hubble discovered his redshift relation a few years later, it was heralded as proof of an expanding spacetime, and an affirmation of the FLRW model.

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 # that the abundance of primordial elements (the amount of H, He, and Li in the Universe) can be calculated from the model to match observations.
-The trouble is, there is now amassing evidence that each of these assumptions is either false, or only true-ish. Recent data can only be accommodated by adjusting an increasing number of free parameters in the model, making it increasingly unwieldy and less and less "elegant" as time goes on. As a consequence of this fudge-factoring, over the last 50 years or so an increasing number of artifacts have been postulated in order to paper over the numbers required to make the model work. These things, in rough order, are:
+The trouble is, there is now amassing evidence that each of these assumptions is either false, or only true-ish. Recent data can only be accommodated by adjusting an increasing number of free parameters in the model, making it increasingly unwieldy and less and less "elegant" as time goes on. In addition, adjusting these parameters to make one set of observations fit (for example, element abundances) results in another set being thrown wildly out (large scale homogeneity). As a consequence of this fudge-factoring, over the last 50 years or so an increasing number of artifacts have been postulated in order to paper over the numbers required to make the model work. These things include:
 # black holes,

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 == What is wrong with cosmology? ==
-The current scientific consensus on the nature and evolution of the Universe is that all the matter and energy in the Universe spontaneously exploded outward as a ''Big Bang'' from a single point in space, and has continued to expand ever since. This model was formulated at a time when scientists were not even sure there were galaxies outside our own Milky Way. However, the truly colossal advancements in observational astronomy over the last 50 years, from ground-based telescopes, satellites, and space-probes to the revolutionary advances in data processing and computing power, have lead to a seldom-admitted crisis of theory versus observation in cosmology.
+The current scientific consensus on the nature and evolution of the Universe is that all the matter and energy in the Universe spontaneously exploded outward as a ''Big Bang'' from a single point in space, and has continued to expand ever since. This model was formulated at a time when scientists were not even sure there were galaxies outside our own Milky Way. However, the truly colossal advancements in observational astronomy over the last 50 years, from ground-based telescopes, satellites, and space-probes to the revolutionary advances in data processing and computing power, have led to a seldom-admitted crisis of theory versus observation in cosmology.
 The current model, referred to as the Lamba Cold Dark Matter (ΛCDM) model, is based on these assumptions and observations: