Astronomers’ quest to understand features of the early universe and how it originated includes making “maps” of leftover radiation from the cosmic creation event. Such maps have provided exquisite details of the universe’s early history and have affirmed the big bang model. The most recent mapmaking work comes from a telescope set in a cold, high-altitude South American desert and its results stand to strengthen evidence for cosmic creation and cosmic design.
Prior to this effort, both the WMAP and Planck spacecraft have delivered amazingly precise maps of the radiation remaining from the cosmic creation event. However, the Atacama Cosmology Telescope (ACT),a ground-based telescope, has produced an equally impressive map.
I wrote about an announcement of this map by the ACT research collaboration on August 10, 2020. Since then, the collaboration’s initial preprint has been updated, peer reviewed, and published in two papers.1 The results are even more impressive than what I reported last August.
The ACT is able to deliver maps of the cosmic microwave background radiation (the radiation remaining from the cosmic creation event) equal in quality to those produced by the WMAP and Planck spacecraft because of its location. It resides at an altitude of 5,190 meters (17,030 feet) in the driest temperate region on Earth, the high-altitude part of the Atacama Desert in northern Chile.
Water vapor in the atmosphere is the primary factor limiting the quality of millimeter wavelength observations (the cosmic microwave background radiation is brightest at millimeter wavelengths). The hyper-dry conditions at the ACT site explains why the ACT can compete with the WMAP and Planck spacecraft.
Readers who have tracked big bang evidence over the years will appreciate the technical details and how the measurements have progressed to strengthen the model. If that’s not you, feel free to skim, glean what you can, and pick it up again at Promising Future.
The ACT Collaboration (a team of more than 40) published its analysis of the fourth ACT data release (DR4). The DR4 has about four times as much data as the DR3. The DR4 includes temperature and polarization measurements of the cosmic microwave background radiation for half the sky at 98 and 150 gigahertz, corresponding to wavelengths of 3 and 2 millimeters, respectively. For 15% of the sky the DR4 includes especially sensitive measurements.
Cosmological Results
ACT’s DR4 provides a data set that is independent of the data sets from both the WMAP and Planck spacecraft. The ACT measurements, for example, cover different ranges of angular scales.
As was the case with the analyses of the WMAP and Planck data sets, the ACT Collaboration’s analysis of DR4 provided an excellent fit with the standard big bang creation model. This model, known as the ΛCDM model, describes a big bang universe that is primarily dominated by dark energy, Λ, and secondarily by cold dark matter, CDM. With respect to the ΛCDM model, the ACT Collaboration wrote that “We find no evidence for deviations.”2
Combining their analysis with that from the Planck Collaboration, the ACT Collaboration produced the most precise measurements to date of the most important cosmological parameters related to the cosmic creation event and the subsequent history of the universe. These cosmological parameters are as follows:
Age of the universe
13.791 ± 0.021 billion years
Cosmic expansion rate
67.53 ± 0.56 kilometers/second/megaparsec
Dark energy density
0.6871 ± 0.0078 of the total cosmic density
Total matter density
0.3115 ± 0.0034 of the total cosmic density
Dark matter density
0.2625 ± 0.0034 of the total cosmic density
Primordial helium abundance
1.0019 ± 0.0046 of the big bang predicted amount
Departure from flat geometry
–0.001 ± 0.011
Scalar spectral index
0.9691 ± 0.0041
A universe with a flat geometry is one that has zero spatial curvature. The ΛCDM model predicts that the universe will measure a departure from a flat geometry of no more than 1%.
The scalar spectral index determines whether or not the universe had an inflation event very early in its history and, if so, what kind of inflation event it experienced. An early cosmic inflation event entails that the universe expands by at least 100 trillion trillion times sometime between 10-36 and 10-32 seconds after its inception.
If the scalar spectral index measures to be 1.0 or greater, then the universe did not experience an inflation event. If the scalar spectral index measures to be exactly equal to 0.95, then the universe experienced a simple cosmic inflation event. If the scalar spectral index measures to be between 0.96 and 0.97, then the universe experienced a complex inflation event.
A combined analysis of the latest ACT and Planck data sets establishes beyond any reasonable doubt that a cosmic inflation event indeed occurred. The probability of it not having occurred is less than 1 chance in 100 billion. This outcome is expected, since in the context of big bang cosmology, only an early cosmic creation event would permit the future existence of physical life.3 The analysis of the ACT and Planck data sets strongly establishes that the cosmic inflation event was complex and not simple. A simple cosmic inflation event is ruled out at a confidence level of 99.999%.
Promising Future
Though the WMAP and Planck spacecraft missions are complete, the ACT will pile up additional data for years to come. By the end of 2021, the ACT Collaboration, for the first time for any instrument, will be able to produce far superior cosmological constraints from polarization measurements than from temperature measurements. This prospect means that additional and stronger consistency checks on big bang creation models will be forthcoming, particularly so for the details on the cosmic inflation event. Already, the ACT Collaboration achievements wonderfully illustrate that the more we learn about the universe, the more evidence we accumulate for what the Bible declared thousands of years ago about the universe’s origin and history.
Endnotes
Simone Aiola et al., “The Atacama Cosmology Telescope: DR4 Maps and Cosmological Parameters,” Journal of Cosmology and Astroparticle Physics 2020, no. 12 (December 2020): id. 047, doi:10.1088/1475-7516/2020/12/047; Steve K. Choi et al., “The Atacama Cosmology Telescope: A Measurement of the Cosmic Microwave Background Power Spectra at 98 and 150 GHz,” Journal of Cosmology and Astroparticle Physics 2020, no. 12 (December 2020): id. 045, doi:10.1088/1475-7516/2020/12/045.
Aiola et al., “The Atacama Cosmology Telescope: DR4 Maps,” page 1 of the paper.
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