My colleague Fazale (Fuz) Rana has been full-time with me at Reasons to Believe (RTB) for the past 22 years. As a biochemist, he loves to speak and write about the complex designs in biological systems. The complex designs compel him to use words and terms with six or more syllables that nonscientists have little clue what they mean. Many of us at RTB tease Fuz that he must be a charismatic Christian because he speaks in an unknown language.
Biochemists are not alone in using vocabulary that few outside their discipline comprehend. It is happening more and more in my discipline of astrophysics. In titling this article about a major cosmological discovery, I found that there was no way to avoid using the term baryon acoustic oscillations. I know from experience that the term can be intimidating for non-astronomers. However, the term describes a relatively simple cosmological phenomenon, one that has profound significance for affirming the biblically predicted big bang creation model.1
Baryon Acoustic Oscillations
Baryons is a catchall term for protons and neutrons. Baryons comprise 99.97% of all the ordinary matter (matter that strongly interacts with photons) in the universe. Hence, astronomers consider baryonic matter and ordinary matter as interchangeable terms.
Everyone familiar with modern entertainment devices knows that acoustic refers to sound. In big bang cosmology, propagation of sound waves in the early universe imprints density fluctuations on the universe’s ordinary matter. Astronomers refer to these fluctuations as baryon acoustic oscillations (BAOs).
In big bang cosmology, galaxies preferentially form in regions of high baryonic density. Therefore, astronomers can measure the universe’s BAOs by using galaxy surveys where they measure the positions and velocities of millions of galaxies. Through accurate determinations of the universe’s BAOs, astronomers can test the validity of the big bang creation model and determine the values of multiple cosmological features. Those features include the cosmic expansion rate, the age of the universe, the geometry of the universe, the nature of dark energy and dark matter (matter that does not interact or very weakly interacts with photons), and the sum of neutrino masses.
Previous Cosmological Implications
For more than two decades, astronomers have been actively measuring the universe’s BAOs with the goal of unambiguously determining the origin and history of the universe. The Baryon Oscillation Spectroscopic Survey (BOSS), a subset of the Sloan Digital Sky Survey (SDSS) has two stated objectives: (1) to measure cosmological parameters to one-percent precision through measurements of 1.5 million or more luminous galaxies within the redshift range z = 0.2–0.7 and (2) to obtain measurements of 160,000+ quasars within the redshift range z = 0.8–3.5. These redshift ranges correspond to 2.47–6.43 billion light-years away (2.47–6.43 billion years ago) and 6.97–12.00 billion light-years away (6.97–12.00 billion years ago), respectively.
In 2015, the BOSS Collaboration published their analysis of the SDSS-III BOSS data release.2 Their analysis yielded a cosmic expansion rate (the Hubble constant) of 67.3 +/- 1.1 kilometers/second/megaparsec (1 megaparsec = 3.26156 million light-years). This cosmic expansion rate translates into an age for the universe = 14.53 +/- 0.24 billion years. They determined that matter comprised 30.1 +/- 0.8% of the universe and dark energy 72 +/- 3%. They measured the curvature of the universe to be -0.003 +/- 0.003 where 0.0 is a perfectly flat universe.
Using a later BOSS data release and a more sophisticated analysis, and assuming a ⋀CDM cosmic creation model (big bang creation model where the dominant component of the universe is dark energy, ⋀, and the next most dominant component is cold dark matter, CDM) astronomers Levon Pogosian, Gong-Bo Zhao, and Karsten Jedamzik found that the Hubble constant = 69.6 +/- 1.8 kilometers/second/megaparsec.3 Using the same data set and assuming that dark energy is governed by a single nonvarying constant, astronomers Rafael Nunes, Santosh Yadav, J. F. Jesus, and Armando Bernui determined that the Hubble constant = 69.23 +/- 0.50 kilometers/second/megaparsec.4
Cosmological Implications of the Latest BAO Data
The recently released SDSS-IV extended BOSS includes measurements on 1,372,737 galaxies over the redshift range z = 0.2–0.75; 174,816 luminous red galaxies in the redshift range 0.6–1.0; 343,708; quasars in the redshift range 0.8–2.2; and 157,845 quasars that are free of broad absorption spectral lines in the redshift range 2.0–3.5. Analysis of data from the completed SDSS-IV extended BOSS yields the following cosmological results.5 Based on the BAO data alone, dark-energy-free cosmic models are ruled out. In combination with maps of the cosmic microwave background radiation (CMBR—the radiation left over from the cosmic creation event), the dark energy density is determined to 0.7% precision. The Hubble constant = 68.18 +/- 0.79 kilometers/second/megaparsec. The universe’s curvature = -0.0022 +/- 0.0022. The combination of the latest BAO data with the latest CMBR data yields a measure of the universe’s curvature = -0.0001 +/- 0.0018. The latter measure ranks as the best measurement to date of the universe’s geometry and provides strong evidence for a flat cosmic geometry.
The Hubble constant is one of the most, if not the most, basic cosmological parameters because it yields absolute determinations of the age of the universe and the universe’s energy content. The Hubble constant measurement of 68.18 +/- 0.79 kilometers/second/megaparsec is by far the most accurate measurement based on mid-range objects, that is, objects at look-back times midway between the earliest times in cosmic history and the latest times. Measurements based on maps of the CMBR reveal the cosmic expansion rate shortly after the universe’s beginning. Measurements based on local galaxies reveal the current cosmic expansion rate.
Based on the final Planck data release, the highest quality map of the CMBR, astronomers determined the Hubble constant = 67.36 +/- 0.54 kilometers/second/megaparsecs.6 Based on using the tip of the red giant branch stars to calibrate distances to type Ia supernovae in local galaxies, astronomers ascertained the Hubble constant = 69.8 +/- 0.8 kilometers/sec/megaparsec.7 Ignoring probable statistical and systematic errors, the three measurements imply that the cosmic expansion rate sped up by 0.82 kilometers/second/megaparsec (1.2%) during the first 5–7 billion years of cosmic history and by another 1.62 kilometers/second/megaparsec (2.3%) during the following 7–9 billion years (a total of 3.5%).
Astronomers expect some speed-up in the cosmic expansion rate because, as the space surface of the universe gets larger, dark energy becomes more effective in its capacity to accelerate the cosmic expansion rate. Meanwhile, as massive bodies in the universe spread apart as a result of cosmic expansion, gravity becomes progressively weaker in its capacity to slow down cosmic expansion. However, assuming that dark energy is governed by a nonvarying constant, the cosmological constant, the cosmic expansion rate should increase by no more than 1% over the entire history of the universe. (In next week’s post, I will explain how different astronomy research groups propose to close the remaining 2.5% gap.)
As the BOSS Collaboration repeatedly demonstrated in their published paper, their analysis of the SDSS-IV extended BOSS data made for an even stronger case for the ⋀CDM big bang model. Astronomers’ analysis of the recent SDSS-IV extended BOSS data release provides yet another example that the more we learn about the origin, history, and structure of the universe and the more accurately we measure the characteristic features of the universe, the more evidence we accumulate for the biblically predicted cosmic creation model.
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Hugh Ross and John Rea, “Big Bang—The Bible Taught It First,” Facts for Faith (Quarter 3, 2000): 26–32; Hugh Ross, “Does the Bible Teach Big Bang Cosmology?” Today’s New Reason to Believe (blog), August 26, 2019.
Éric Aubourg et al., BOSS Collaboration, “Cosmological Implications of Baryon Acoustic Oscillation Measurements,” Physical Review D 92 (December 14, 2015): id. 123516, doi:10.1103/PhysRevD.92.123516.
Levon Pogosian, Gong-Bo Zhao, and Karsten Jedamzik, “Recombination-Independent Determination of the Sound Horizon and the Hubble Constant from BAO,” Astrophysical Journal Letters 904, no. 2 (December 2020): id. L17, doi:10.3847/2041-8213/abc6a8.
Rafael C. Nunes et al., “Cosmological Parameter Analysis Using Transversal BAO Data,” Monthly Notices of the Royal Astronomical Society 497, no. 2 (September 2020): 2133–2141, doi:10.1093/mnras/staa2036.
Shadab Alam et al., eBOSS Collaboration, “Completed SDSS-IV Extended Baryon Oscillation Spectroscopic Survey: Cosmological Implications from Two Decades of Spectroscopic Surveys at the Apache Point Observatory,” Physical Review D 103 (April 28, 2021): id. 083533, doi:10.1103/PhysRevD.103.083533.
N. Aghanim et al., Planck Collaboration, “Planck 2018 Results. VI. Cosmological Parameters,” Astronomy & Astrophysics 641 (September 2020): id. A6, doi:10.1051/0004-6361/201833910.
Wendy L. Freedman et al., “The Carnegie-Chicago Hubble Program. VIII. An Independent Determination of the Hubble Constant Based on the Tip of the Red Giant Branch,” Astrophysical Journal 882, no. 1 (September 1, 2019): id. 34, doi:10.3847/1538-4357/ab2f73.