Ever since it was proposed a century ago, the big bang creation model has been under scrutiny and ongoing refinement. Discordance between a measurement of the cosmic expansion rate based on nearby galaxies and one based on the cosmic microwave background radiation has led to tension concerning the cosmic creation event and subsequent history of the universe. However, new cosmic parameter measurements and adjustments stand to resolve the concern.

The Hubble constant is the rate at which the universe expands. It is the most important characteristic of the universe for determining a correct cosmic creation model. It is the cosmic feature of the universe that first established the universe must have a beginning, one that implies a Beginner. It reveals what components comprise the universe and how these components are designed to make possible the existence of life, especially advanced life. The Hubble constant has the potential of unveiling additional design features in the laws and constants of physics.

Hubble Constant Tension
The standard big bang creation model (abbreviated the ⋀CDM model) is where dark energy governed by the cosmological constant (⋀) is the dominant component of the universe and cold dark matter (CDM) is the next most dominant cosmic component. This model predicts that the cosmic expansion rate will speed up by 0.6–1.0% from the beginning of the universe 13.79 billion years ago until the present moment. One reason why is that the power of dark energy to accelerate the cosmic expansion rate increases as the cosmic space surface grows larger. Another reason is that as the universe expands, massive bodies in the universe spread apart, which weakens the effect of gravity to slow down the cosmic expansion rate. Indeed, astronomers have detected a transition from a slowly decelerating cosmic expansion rate to a slowly accelerating cosmic expansion rate when the universe was about 9 billion years old (about 5 billion years ago).

Astronomers’ measurements, however, divulge a discrepancy in cosmic expansion rate measurements. Two years ago, a team led by Nobel laureate Adam Riess used Cepheid variable stars to calibrate the distances to local galaxies hosting type Ia supernovae. Based on this calibration, Riess’s team determined that the universe is expanding at a rate of 74.03 ± 1.42 kilometers/second/megaparsec.1 (1 megaparsec = 3.26 million light-years.) This value differs, however, from the one based on a detailed map of cosmic microwave background radiation (CMBR), a map that reveals the state of the universe when it was only 380,000 years old. The CMBR-based cosmic expansion rate = 67.4 ± 0.5 kilometers/second/megaparsec.2 The difference of 6.6 kilometers/second/megaparsec is 4.7 times the probable error in the measurement by Riess’s team. Astronomers refer to this difference as the Hubble constant tension.

The tension arises from the notion that such a large discrepancy is very unlikely to be a statistical outlier. Rather, it is due to one or more overlooked systematic effects (instrumental issues in the telescopes used to make the observations and/or physical properties in the astronomical objects observed that push all the measurements either above or below the true value) and/or unforeseen laws or constants of physics. A few have even asserted that the Hubble constant tension implies “there is something seriously wrong with the big bang model”3 or that “the big bang model is false.”4

Resolving the Tension: Observations
Astronomers possess a second, independent method for calibrating distances to type Ia supernovae. That method is to use tip of the red giant branch (TRGB) stars instead of Cepheid variable stars. A year and a half ago, a team of 13 astronomers determined the current cosmic expansion rate based on TRGB stars. Their value for the Hubble constant = 69.8 ± 0.8 kilometers/second/megaparsec.5 This value differs from the CMBR-based cosmic expansion rate by 2.4 kilometers/second/megaparsec.

The team argued that it is more likely that systematic effects have a greater impact on the Cepheid variable star method than they do on the TRGB method. Nevertheless, some tension remained. With the smaller error bar, the difference between CMBR and TRGB measures of the Hubble constant is 3.0 times the probable error in the TRGB measurement. Taking into account that astronomical measurements of the matter and dark energy density predict that the CMBR Hubble constant value should be about 0.5 kilometers/second/megaparsec lower than the TRGB Hubble constant value, it is possible that the remaining difference of about 1.9 kilometers/second/megaparsec could be statistical. In that case, higher precision measurements will remove the tension.

A recent indication that the remaining difference indeed may be a statistical artifact comes from the measurement of the Hubble constant based on baryon acoustic oscillations (BAO) that I described in last week’s article.6 The BAO measurement gives the Hubble constant value when the universe is roughly half its present age. The value I reported was 68.18 ± 0.79 kilometers/second/megaparsec. This value is 1.2% greater than the CMBR Hubble constant value and 2.3% less than the TRGB Hubble constant value.

A local matter (galaxies, galaxy clusters, dark matter) underdensity would generate an increase in the local value of the cosmic expansion rate. If the density of galaxies, galaxy clusters, and dark matter in the local region of the universe is approximately 10% less than the average for the rest of the present-day universe, that underdensity would produce about a 2% higher value for the Hubble constant. A 2% higher value for the local Hubble constant measurement would not relieve the tension between the CMBR and Cepheid variable star Hubble constant measurements but it does fully eliminate the tension between the CMBR and TRGB Hubble constant measurements.

Astronomers have made observations that establish, beyond doubt, that a local matter underdensity does exist.7 Several observational studies indicate that the underdensity appears sufficient to remove tension among the best CMBR, BAO, and TRGB Hubble constant measurements in the context of the best measurements for the cosmic dark energy and matter densities.8

Resolving the Tension: Cosmic Parameters Adjustments
While the observations of the local matter underdensity appear to resolve the best CMBR, BAO, and TRGB Hubble constant measurements, making minor adjustments to a few cosmic parameters provides alternate ways to resolve the Hubble constant tension. In the standard big bang ⋀CDM model dark energy is governed by a single nonvarying constant. However, if the dark energy equation of state does vary as the universe ages, even slightly, then in all conceivable contexts there is no Hubble constant tension.9 In the words of a research team led by Rafael Nunes, “There is no tension on H0 [Hubble constant] estimates in this dynamical DE [dark energy] context.”10

Whether the dark energy equation of state varies or does not vary over the history of the universe will soon be settled. As I explained in Neutron Star Mergers, Part 1: Evidence for Creation, observations of binary neutron star merger events will yield accurate, assumption-free measurements of the cosmic expansion rate at look-back times ranging from the present to at least 12 billion years ago.11

Three additional cosmic parameter adjustments would successfully resolve the Hubble constant tension. The first would be a slightly earlier time than 375,000 years after the cosmic creation event for the universe to cool sufficiently for hydrogen atoms to form.12 A second adjustment would be for the curvature of the universe to depart very slightly from a flat geometry.13 A third adjustment would be a slightly different bound on neutrino masses.14 All of these adjustments can be tested for their possible validity by more accurate CMBR maps, observations of more binary neutron star merging events, and more extensive and accurate BAO and TRGB measurements.

Philosophical Implications
The latest cosmological observations and proposed cosmic parameter adjustments provide multiple independent ways the Hubble constant tension can be eliminated. The biblically predicted big bang creation model is not in trouble. The latest observations demonstrate 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 supernatural design of the universe and for the big bang creation model.

Check out more from Reasons to Believe @Reasons.org

Endnotes

  1. Adam G. Riess et al., “Large Magellanic Cloud Cepheid Standards Provide a 1% Foundation for the Determination of the Hubble Constant and Stronger Evidence for Physics Beyond ΛCDM,” Astrophysical Journal 876, no. 85 (May 1, 2019), id. 85, doi:10.3847/1538-4357/ab1422.
  2. Planck Collaboration, “Planck 2018 Results. VI. Cosmological Parameters,” arXiv:1807.06209 (submitted July 2018, accepted for publication in Astronomy and Astrophysics, manuscript no. ms September 24, 2019), https://arxiv.org/pdf/1807.06209.pdf.
  3. Danny R. Faulkner, “The Newest Finding on the Expansion of the Universe,” Answers in Genesis (May 10, 2019).
  4. Faulkner, “The Newest Finding.”
  5. 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.
  6. Hugh Ross, “Baryon Acoustic Oscillations Boost Case for Cosmic Creation,” Today’s New Reason to Believe (blog), July 26, 2021, https://reasons.org/explore/blogs/todays-new-reason-to-believe/baryon-acoustic-oscillations-boost-case-for-cosmic-creaton.
  7. R. Brent Tully et al., “Cosmicflows–3: Cosmography of the Local Void,” Astrophysical Journal 880, no. 1 (July 20, 2019): id. 24, doi:10.3847/1538-4357/ab2597; Benjamin L. Hoscheit and Amy J. Barger, “The KBC Void: Consistency with Supernovae Type Ia and the Kinematic SZ Effect in a ⋀LTB Model,” Astrophysical Journal 854, no. 1 (February 10, 2018): id. 46, doi:10.3847/1538-4357/aaa59b; R. Brent Tully et al., “Our Peculiar Motion Away from the Local Void,” Astrophysical Journal 676, no. 1 (March 20, 2008): id. 184, doi:10.1086/527428.
  8. L. Kazantzidis and L. Perivolaropoulos, “Hints of a Local Matter Underdensity or Modified Gravity in the Low z Pantheon Data,” Physical Review D 102, no. 2 (July 15, 2020): id. 023520, doi:10.1103/PhysRevD.102.023520; Vladimir V. Luković, Balakrishna S. Haridasu, and Nicola Vittorio, “Exploring the Evidence for a Large Local Void with Supernovae Ia Data,” Monthly Notices of the Royal Astronomical Society 491, no. 2 (January 2020): 2075–2087, doi:10.1093/mnras/stz3070.
  9. Balakrishna S. Haridasu, Matteo Viel, and Nicola Vittorio, “Sources of H0-Tension in Dark Energy Scenarios,” Physical Review D 103, no. 6 (March 15, 2021): id. 063539, doi:10.1103/PhysRevD.103.063539; Rafael C. Nunes et al., “Cosmological Parameter Analyses Using Transversal BAO Data,” Monthly Notices of the Royal Astronomical Society 497, no. 2 (September 2020): 2133–2141, doi:10.1093/mnras/staa2036.
  10. Nunes et al., “Cosmological Parameter Analyses,” 2133.
  11. Hugh Ross, “Neutron Star Mergers, Part 1: Evidence for Creation,” Today’s New Reason to Believe (blog), July 12, 2021.
  12. Luke Hart and Jens Chluba, “Updated Fundamental Constant Constraints from Planck 2018 Data and Possible Relations to the Hubble Tension,” Monthly Notices of the Royal Astronomical Society 493, no. 3 (April 2020): 3255–3263, doi:10.1093/mnras/staa412; Toyokazu Sekiguchi and Tomo Takahashi, “Early Recombination as a Solution to the H0 Tension,” Physical Review D 103, no. 8 (April 12, 2021): id. 083507, doi:10.1103/PhysRevD.103.083507.
  13. Benjamin Bose and Lucas Lombriser, “Easing Cosmic Tensions with an Open and Hotter Universe,” Physical Review D 103, no. 8 (April 27, 2021): id. L081304, doi:10.1103/PhysRevD.103.L081304.
  14. Toyokazu Sekiguchi and Tomo Takahashi, “Cosmological Bound on Neutrino Masses in the Light of H0 Tension,” Physical Review D 103, no. 8 (April 20, 2021): id. 083516, doi:10.1103/PhysRevD.103.083516,

About The Author

Dr. Hugh Ross

Reasons to Believe emerged from my passion to research, develop, and proclaim the most powerful new reasons to believe in Christ as Creator, Lord, and Savior and to use those new reasons to reach people for Christ. I also am eager to equip Christians to engage, rather than withdraw from or attack, educated non-Christians. One of the approaches I’ve developed, with the help of my RTB colleagues, is a biblical creation model that is testable, falsifiable, and predictive. I enjoy constructively integrating all 66 books of the Bible with all the science disciplines as a way to discover and apply deeper truths. 1 Peter 3:15–16 sets my ministry goal, "Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect, keeping a clear conscience." Hugh Ross launched his career at age seven when he went to the library to find out why stars are hot. Physics and astronomy captured his curiosity and never let go. At age seventeen he became the youngest person ever to serve as director of observations for Vancouver's Royal Astronomical Society. With the help of a provincial scholarship and a National Research Council (NRC) of Canada fellowship, he completed his undergraduate degree in physics (University of British Columbia) and graduate degrees in astronomy (University of Toronto). The NRC also sent him to the United States for postdoctoral studies. At Caltech he researched quasi-stellar objects, or "quasars," some of the most distant and ancient objects in the universe. Not all of Hugh's discoveries involved astrophysics. Prompted by curiosity, he studied the world’s religions and "holy books" and found only one book that proved scientifically and historically accurate: the Bible. Hugh started at religious "ground zero" and through scientific and historical reality-testing became convinced that the Bible is truly the Word of God! When he went on to describe for others his journey to faith in Jesus Christ, he was surprised to discover how many people believed or disbelieved without checking the evidence. Hugh's unshakable confidence that God's revelations in Scripture and nature do not, will not, and cannot contradict became his unique message. Wholeheartedly encouraged by family and friends, communicating that message as broadly and clearly as possible became his mission. Thus, in 1986, he founded science-faith think tank Reasons to Believe (RTB). He and his colleagues at RTB keep tabs on the frontiers of research to share with scientists and nonscientists alike the thrilling news of what's being discovered and how it connects with biblical theology. In this realm, he has written many books, including: The Fingerprint of God, The Creator and the Cosmos, Beyond the Cosmos, A Matter of Days, Creation as Science, Why the Universe Is the Way It Is, and More Than a Theory. Between writing books and articles, recording podcasts, and taking interviews, Hugh travels the world challenging students and faculty, churches and professional groups, to consider what they believe and why. He presents a persuasive case for Christianity without applying pressure. Because he treats people's questions and comments with respect, he is in great demand as a speaker and as a talk-radio and television guest. Having grown up amid the splendor of Canada's mountains, wildlife, and waterways, Hugh loves the outdoors. Hiking, trail running, and photography are among his favorite recreational pursuits - in addition to stargazing. Hugh lives in Southern California with his wife, Kathy, and two sons.



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