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astronomy Cosmology Physics Science

No CMB shadows: an argument against the big bang that can no longer be sustained

I have previously made the argument that the cosmic microwave background (CMB) radiation, ‘light’ allegedly from the big bang fireball, casts no shadows in the foreground of galaxy clusters.1 If the big bang were true, the light from the fireball should cast a shadow in the foreground of all galaxy clusters. This is because the source of the CMB radiation, in standard big bang cosmology, is what is known as the “last scattering surface“.

The last scattering surface is the stage of the big bang fireball that describes the situation when big bang photons cooled to about 1100 K. At that stage of the story those photons separated from the plasma that had previously kept them bound. Then expansion of the universe is alleged to have further cooled those photons to about 3 K, which brings them into the microwave band. Thus if these CMB photons cast no shadows in front of all galaxy clusters it spells bad news for the big bang hypothesis.

Fig 1: Schematic of the Sunyaev-Zel’dovich effect that results in an increase in higher energy (or blue shifted) photons of the CMB when seen through the hot gas present in cluster of galaxies. Credit: astro.uchicago.edu/sza/primer.html

The CMB radiation shadowing effect, or more precisely the cooling effect, by galaxy clusters is understood in terms of the Sunyaev–Zel’dovich Effect (SZE). This is where microwave photons are isotropically scattered by electrons in the hot inter-cluster medium (ICM) (see Fig. 1) via an inverse Compton process leaving a net decrement (or cooling) in the foreground towards the observer in the solar system. Of those CMB photons coming from behind the galaxy cluster less emerge with the same trajectory due to the scattering. Even though the scattered photons pick up energy from the ICM the number of more energetic CMB photons is reduced. After modelling what this new CMB photon energy (hence temperature) should be, a decrement can, in principle, be detected.

Starting around 2003 some published investigations, using this SZE, looked for the expected shadowing/cooling effect in galaxy clusters. No significant cooling effect was found, by multiple studies, including the WMAP satellite data.2 This was considered to be very anomalous, significantly different from what was expected if the CMB radiation was from the big bang fireball. The anomaly was even confirmed by the early Planck satellite survey data in 2011.3

Categories
astronomy Cosmology Physics

You’re not lost in a directionless universe

A news article in appeared in Science titled “It’s official: You’re lost in a directionless universe”1 where the author Adrian Cho reported on the results of a research paper published in Physical Review Letters in September 2016. That paper is available online as a preprint.In the online Science article the conclusion of the research is stated that

“For the first time, we really exclude anisotropy,” [the lead author] Saadeh says. “Before, it was only that it hadn’t been probed.”

universe_cmb
Top image: CMB temperature anisotropies map from Planck satellite. Bottom image: Simulated image from one of the models used where a preferred axis was introduced. Credits: (Top to bottom) ESA and the Planck Collaboration; D. Saadeh et. al., zenodo

The research involved simulations on a supercomputer where various forms of anisotropic structure and expansion of the universe were introduced in modelled universes. The authors looked for how those would affect any putative patterns that might be observed in the cosmic microwave background (CMB) radiation. The design was to see what would produce anisotropy in the CMB temperature data. See illustration to the right.

They found that none of the patterns they produced are observed in the CMB data from the Planck satellite. Ok, so that solves it! The Universe is isotropic and therefore the fundamental assumption for the big bang model—that is, matter is distributed uniformly throughout the Universe, on the largest scales–is correct and hence it validates the choice of the standard ΛCDM big bang model to describe the Universe. Well, no, not actually.

Firstly, for that to be true it would have to be assumed that the authors modelled all possible sources of anisotropy in the Universe. It would also have to be assumed that the patterns they generated in their modelled CMB temperature anisotropies were, in fact, indicative of large scale structure in the real Universe. There is no independent way to test that. All that researchers have available to them is supercomputer modelling. So how can you know what the Universe should look like with different types of anisotropic distributions of matter? There are no other universes available except this one, therefore we are always limited by this fundamental uncertainty.