The Observable Universe and Beyond

Wilkinson Microwave Anisotropy Probe (WMAP) and ESA/Planck

The Wilkinson Microwave Anisotropy Probe (WMAP) team has released the first detailed full-sky map of the oldest light in the universe on February 11, 2003. Figure 02-09aa shows the measurements with red indicates "warmer" and blue indicates "cooler" spots. The patterns in the map are tiny temperature differences within an extraordinarily evenly dispersed microwave radiation bathing the Universe, which now averages a frigid 2.73 degrees above absolute zero temperature. WMAP resolves the slight temperature fluctuations, which vary by only millionths of a degree. Analyses of this microwave radiation emitted only 380,000 years after the Big Bang appear to define our universe

Figure 02-09aa High Resolution CMBR
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more precisely than ever before. Measurements from WMAP resolve several long-standing disagreements in cosmology rooted in less precise data.

Specifically, present analyses of the WMAP all-sky image indicate that the universe is 13.7 billion years old (accurate to 1 percent), composed of 73 percent dark energy, 23 percent cold dark matter, and only 4 percent atoms, is currently expanding at the rate of 71 km/sec/Mpc (accurate to 5 percent), underwent episodes of rapid expansion called inflation, the geometry of the Universe is flat¹, and will expand forever. The Wilkinson Microwave Anisotropy Probe was launched on June 30, 2001. It is designed to operate for four years. Actually, it lasted much longer until October, 2010. The James Webb Space Telescope (JWST) is supposed to take its place in 2011. The project has been delayed until 2013 or later. Meanwhile, ESA's Planck spacecraft, launched on the May 14, 2009, is taking more refined measurements both in total intensity and polarization in a different wavelength range

(1 - 0.033 cm). It will yield the most accurate map yet of the CMBR. The first image of a strip of the millimeter wavelength sky (Figure 02-09ab, from Planck in September 2009) shows that all systems are working well. Routine operations will continue for at least 15 months without a break. In this time, Planck will be able to gather data (at 9 different wavelengths) for two full independent all-sky maps. To fully exploit the high sensitivity of Planck, the data will require a great deal of delicate calibrations and careful analysis. It will keep cosmologists and astrophysicists busy for decades to come.

Figure 02-09ab First Image from the Planck Satellite

See Planck Update below from an ESA news about the latest (2013) cosmic parameters.

Further analysis of the WMAP data in 2007 reveals two oddities:

1. It has been deduced from the absence of radio sources that there is a big hole in the sky devoid of both normal and dark matter in the direction of the constellation Eridanus. Its size is nearly a billion light years across at a distance 6 - 10 billion light years away (40 times larger in volume than the previous record holder). The void coincides with an extra large cold spot in the WMAP map covering a few degrees of the sky (many times more than the full moon). The temperature of the void is between 20 and 45 % lower

Figure 02-09b WMAP Oddities
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than the average. It is suggested that the discovery of the void ties in neatly with the WMAP cold spot and the existence of dark energy as the photons would lose energy passing through an empty space.

2. WMAP's temperature variations can be decomposed into set of patterns called multipoles. The lowest multipoles are the largest-area, continent- and ocean-size undulations on the temperature map. Higher multipoles are like successively smaller-area plateaus, mountains and hills (and trenches and valleys) inserted on top of the larger features. As shown in Figure 02-09b both the quadrupole and the octupole are aligned along an "axis" (of evil) which standard cosmology cannot explain. This could happen by chance only about 0.1% of the time. Critics have considered a variety of possibilities. One explanation involves some kind of imperfection in WMAP's detector that introduces the patterns, but there is no evidence for this.

The WMAP team stated in 2012 that the "axis of evil" is most likely a statistical fluke.

However, an 2016 article by the title of "The Emptiest Place in Space" confirms the relationship between the abnormally cold spot and a huge void about 3 billion light-years away with a size of ~ 1 billion lys. Both line up on a cone suspended to the anomaly. The colder temperature is explained by the photons moving through an expanding void (Figure 02-09c). This is the largest void detected so far, but it is not clear if it is the emptiest. The original research paper can be found online under the title : "Detection of a Supervoid Aligned with the Cold Spot of the Cosmic Microwave Background".

Anyway back in 2009, a theory based on the multiverse aspect of the string theory claims that the dynamic effect of matter and gravity would have weeded out the majority of string vacuums, leaving only our patch and close neighbours in the string landscape. A calculation shows that interaction between neighbouring patches in early epoch would leave the universes in an entangled state linking them together even when their separation is space-like (meaning they cannot interact with each other in the usual way). It predicts that pushing and squeezing between the patches will produce voids on the scales of about 1/2 billion light year. The alignment in the lower multipoles is the byproduct of such interaction, which squeezes our universe on one side, perhaps shaped it like a pancake. This theory may point us to the first glance of another universe after all kinds of speculation in science fictions.

Figure 02-09c The Void
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		The NASA/WMAP Science Team presents the cosmic microwave temperature fluctuations from the 5-year WMAP data (Figure 02-09d) on March, 2008. The composition of the early universe has been measured from the data as shown in Fiugre 02-09e. It is obvious by comparing with the composition in the current epoch that it varies as the universe expands. It appears that the dark energy density does not
Figure 02-09d WMAP 5-Year Data [large image]	Figure 02-09e Early Universe [view large image]	decrease at all, so it now dominates the universe even though it was a tiny fraction 13.7 billion years ago. Other major findings include:

New evidence that a sea of cosmic neutrinos permeates the universe. Cosmic neutrinos existed in such huge numbers they affected the universe's early development. That, in turn, influenced the microwaves that WMAP observes.
The first stars took more than a half-billion years to create a cosmic fog. The data provide crucial new insights into the end of the "dark ages," when the first generation of stars began to shine. The glow from these stars created a thin fog of electrons in the surrounding gas that scatters microwaves.
The new WMAP data places tight constraints on the theory of inflation. Some versions of the inflation theory now are eliminated. Others have picked up new support.

The 2012 WMAP update produces a slightly different set of cosmic parameters (red in Figure 09-02e), see also the details in the WMAP Table.

The ESA/Planck Collaboration announced their cosmic measurements on March 21, 2013. The results are based on the 15.5 months of data

		collected by the Planck space telescope. As shown in Figure 02-09f, the CMBR map conform well to the simple model of the universe with inflation and expansion. The composition (Figure 02-09g) is slightly different from those by WMAP (2012 data in red). The suspect anomalies in WMAP also show up in the Planck map in the forms of a cold spot (or hole) and an asymmetry in the average temperatures on opposite hemispheres of the sky
Figure 02-09f CMBR Map by Planck [view large image]	Figure 02-09g Planck's Cosmic Measurements	- the axis of evil (white line in Figure 02-09g). The Hubble constant is 67.15 km/sec-Mpc as measured by Planck corresponding to an age of 13.82x10⁹ years for the universe. The map even shows that the number

of neutrino "flavors" permeating the cosmos will probably remain at three. The universe would have expanded more quickly during its first moment if there had been a fourth. The ESA/Planck data shows no sign of "darkflow" as reported in 2008 by analyzing the WMAP data. Its proponents are running their own analysis with the new Planck data and expect to have results in a few months.

The Planck data also reveal a discrepancy in galactic cluster mass as predicted by standard cosmology and measured by the Sunyaev-Zeldovich effect, which bumps up photon energy by interacting with the hot gas in the cluster. Two 2014 studies of gravitational lensing suggest that there is no missing mass as estimated by the Sunyaev-Zeldovich effect (Figure 02-09h). The new measurements yield an average cluster mass of 10¹⁵ M_sun similar to the estimate from Virial Theorem. These reports may disappoint those physicists who desperately look for shred of evidences or flimsy excuses to promote their brand of exotic physics.

Figure 02-09h Galactic Cluster Mass [view large image]

		The Planck team presented the latest CMB analysis (based on all four years of observations) to the press on December 01, 2014 in Ferrara, Italy, during a Planck 2014 conference. It reaffirms the standard model of cosmic evolution, but puts into question AMS's earlier claim on the detection of dark matter. The six major issues (Figure 02-09i) addressed in the conference are described briefly in the followings.
Figure 02-09i Planck 2014-12-01 [view large image]	Figure 02-09j Polarization 2014-12-01 [view large image]

Positrons Excess - AMS observations claims an excess in positron counts beyond 10 Gev. This feature can be explained as the debris of dark matter particles collisions if such events happen more often now than in the distant past. The latest Planck analysis shows that the probability of collision should remain over time, thus rules out the claim of dark matter detection.

Cosmic Inflation - The preliminary Planck data provides support for cosmic inflation in its simplest version which predicts the same number of hot and cold temperature or high and low density spots, e.g., in the form of Gaussian distribution. This kind of distribution produces the galaxies and clusters of galaxies we see today. It leads to the formation of similar structures on all scales (scale invariant) and the CMBR is said to be un-polarized.

Apparent Mismatch between Planck and WMAP Data - The discrepancies include a higher density of matter, a slightly greater variation in the distribution of that matter, and a lower value of the Hubble constant. The new values of these parameters by Planck are now closer to the WMAP's.

Birthday of the First Star - The birthday of the first star is about 400 million years after the Big Bang according to the WMAP data, while the quasar light suggests 700 - 800 million years. The Planck's data favor the quasar value.

Neutrinos - Together with observations from other telescopes, the recent Planck data yield a total mass of less than 0.21 ev for the three known neutrinos types making the existence of a fourth type of neutrino (the proiposed "sterile neutrino") unlikely.

Gravitational Wave from Inflation - The controversial claim on the detection of B-mode polarization (implying G-wave generation from inflation) will be addressed in an upcoming announcement on December 22, 2014. Figure 02-09j depicts the polarization of the cosmic microwave background (in the 70 Gigahertz band) as measured by the Planck space telescope. The all-sky map shows the direction of the polarization as black lines, while the colour scale indicates the polarization intensity, increasing from white to black.

The era of CMB (Cosmic Microwave Background) astronomy began with the discovery in 1965 of a feeble microwave radiation emanating uniformly from all directions in the sky. Since then three spacecrafts (COBE, WMAP, and Planck, Figure 02-09k) have made measurements of its temperature fluctuations in the Power Spectrum. The mission closed on July 17, 2018 when the Planck Collaboration released to the public a new and improved version of the data acquired by the Planck satellite. According to an article in Forbes : "Planck is so sensitive that the limits to what it can

		see aren't set by instruments, which can measure down to 0.07K or so, but by the fundamental astrophysics of the Universe itself! In other words, it will be impossible to ever take better pictures of this stage of the Universe than Planck has already taken." So it could be the end of an era as funding would not be forthcoming for an already completed mission. The conclusion from the latest data confirms that the universe is consistent with the CDM model as portrayed
Figure 02-09k CMB Legacy [view large image]	Figure 02-09l Cosmological CDM Model [view large image]	in Figure 02-09l, i.e., it is mostly composed of vacuum energy and Cold Dark Matter. Their cosmic data are described briefly below :

Dark Energy Density Parameter - = 68.3%. As the w parameter w = -1.03 is found in the current report, it suggests that the vacuum energy denstiy is consistent with the vacuum energy density as prescribed by the constant term in General Relativity. See "Vacuum Energy Density".

Dark Matter Density Parameter - _D = 26.8%, its property is unknown. See "Dark Matter, 2018 Update".

Baryon Density Parameter - _B = 4.9%. See "Insignificance".

Matter Density Parameter - _M = _D + _B = 31.7%.

Hubble Constant - 67.4 (km/sec)/Mpc. This is the only parameter which is not in agreement with other measurements. See "Hubble Tension".

Age of the Universe - 13.8 Gyr. See "Formula for the age of the Universe".

Neutrino - The data indicates 3 family members (namely electron, muon, and tau neutrino, in term of the effective extra relativistic degrees of freedom N_eff = 2.99). There's no room for a 4^th one such as the sterile neutrino. The mass of any individual neutrino species can be no more than 0.04 eV/c². The neutrino background temperature is 1.95 K, i.e., cooler than the CMB photon's 2.726 K. See "Neutrino Oscillation".

Scalar Spectral Index - Many inflationary models predict that the scalar component of the fluctuations obeys a power law of the form :
P_s(k) k^n_s-1, where the wavenumber of the fluctuations k = 2/, and n_s is referred to as the scalar spectral index with n_s = 1 corresponding to scale invariant fluctuations. This parameter describes the initial clumping of matter in space. The clumping in turn produced the galaxies and clusters of galaxies we see today. If n_s ~ 1, the "primordial" perturbations was the same on all physical scales, leading to the formation of similar structures on all scales, their spectrum is said to have no tilt. Planck 2018 reports n_s = 0.965 which is consistent with the simplest inflation models. See "Quantum Fluctuations and Cosmic Structures".

Tensor-Scalar Ratio r - The presence of primordial tensor fluctuations is predicted by many inflationary models. Planck estimates a value of r < 0.07 indicating non-existing or very weak gravitational wave signal. See "Tensor Fluctuation".

Optical Depth - It is a dimensionless parameter measuring the effect of photon collision with electron, which would alter its original path. Planck 2018 comes up with a value of 0.054. See "CMB Parameters, 2008 ".

Curvature of the Universe - It is no greater than 1-part-in-1000, indicating that the Universe is indistinguishable from perfectly flat. See "Types of Universe".

See "How The Planck Satellite Forever Changed Our View Of The Universe" for more detail.

¹Since the inflation has generated a much bigger universe than we can see, the visible universe becomes flat to our perception just like the flat Earth in local view. This implies parallel lines will never meet no matter how far they are extended, and the familiar scenery of galaxies and galaxy clusters would extend infinitely far beyond our cosmic horizon.