Confirming Cosmic Expansion, Part 4 (of 4)
For over two thousand years the Bible stood alone as the only text to claim that the cosmos have been continually expanding under fixed physical laws from the beginning of space, time, matter, and energy.1 Not until the twentieth century did scientists even consider the possibility of continual cosmic expansion. Efforts to further confirm the expansion strengthen the biblical cosmic creation model.
Until just a decade ago, the only accurate methods for determining the cosmic expansion rate relied on the distance ladder method, which uses direct distance measurements on nearby objects to calibrate indirect methods for far away objects. Researchers today still consider this method one of the pillars for calculating the cosmic expansion rate. Yet the distance ladder method had limitations. (For greater detail on this method, see part 1 of this series.)
Skeptics of the biblical big bang creation model have challenged that the indirect methods for measuring the cosmic expansion rate are flawed with systematic effects and, therefore, cannot be trusted to deliver reliable conclusions about the origin, history, and design of the universe. But this challenge has been met.
In just fifteen years astronomers went from having no direct distance measurements for any galaxies to possessing direct calculations by three independent techniques for nineteen different galaxies spread over the distance range of 13 million to 8 billion light-years. This range means astronomers have directly measured the cosmic expansion rate for well over half of the entire history of the universe. The direct methods fully confirm the reliability of the indirect methods to produce accurate calculations of cosmic expansion throughout the past 8 billion years. Moreover, some of the direct distance measurements already exceed the precision of the best indirect determinations.
Part 2 of this series introduced two of the three new techniques: measurements of the expanding shock fronts of supernova eruptions; and observations of water maser sources orbiting about the center of the host galaxy. The former method provides direct distance values for galaxies within 20 million light-years and the latter for galaxies within 200 million light-years. Part 3 briefly explained the third technique, measured time delays of gravitational lenses, which gives precise values for galaxies up to several billion light-years away.
The combination of these three techniques gives astronomers the best unambiguous means for proving that we indeed live in a universe that has continually expanded from the cosmic creation event. It also greatly impacts the creation/evolution debate by allowing researchers to determine the age of the universe (a test of young-earth creationism), the geometry of the universe (a test of multiverse hypotheses), and the nature of dark energy (the dominant component of the universe).
Testing young-earth creationism
The best direct distance measurements leave no doubt that the universe has continuously expanded from the cosmic creation event for 14 billion years. In Genesis 1, the Hebrew word yôm—translated “day”— has four different literal definitions, one of which fits with a 14 billion-year-old universe. However, young-earth creationists presume the appropriate (some would say only) way to define the creation days is as 24-hour days. This is a flawed interpretation of Genesis 1. Rather, cosmic expansion rates confirm the biblical analysis of such noted Hebrew scholars as Gleason Archer, C. John Collins, and Walter Kaiser, who independently point out that in reference to the six creation days, yôm must refer to a long but finite period of time.
Testing multiverse hypotheses
All multiverse models proposed by nontheists, in order to explain the “overwhelming impression of design” and do away with the need for a supernatural Creator, demand that the universe in which we live must manifest an open geometry. Yet the best direct distance measurements independently confirm that the geometry of the universe is either flat or very close to flat. These measurements set the universe’s curvature at -0.031 < Ωk < 0.009. (For perfect flatness Ωk = 1.0.). The Wilkinson Microwave Anisotropy Probe (WMAP) five-year data set constrained the curvature of the universe to be -0.0170 < Ωk < 0.0068. These two independent determinations are consistent with one another, as well as consistent with a flat cosmic geometry. There is room within the measurements for a cosmic geometry that is either slightly negative (closed) or slightly positive (open). Even so, the evidence favors a closed geometry more strongly than an open geometry.
Determining the nature of dark energy
Dark energy comprises about 72 percent of all the stuff that makes up the universe, making it the dominant component of the universe—yet its nature and characteristics have remained largely a mystery. Astronomers continue attempts to determine the nature of dark energy by measuring the equation of state for the universe. This equation of state is characterized by a dimensionless number (the “w parameter”), which is equal to the ratio of cosmic pressure to cosmic energy density. If w = -1, then dark energy is described by a cosmological constant. If w significantly departs from -1, then dark energy is described by “quintessence.” This quintessence can be one of two things: (1) a factor that varies over the history of the universe; or (2) a time-varying factor plus one or more physical constants that may or may not include a cosmological constant
The philosophical significance of dark energy’s nature concerns fine-tuning, which makes physical life possible. If dark energy is indeed described by a cosmological constant, then that constant must be within one part in 10122 for life to be possible. This degree of fine-tuning design is by far the greatest yet determined anywhere in the sciences. It exceeds human engineers’ greatest degree of fine-tuning design by a factor of 1097 times.
The case for dark energy described by a cosmological constant represents the best-known fine-tuning design example in science. Observations by astronomers via two independent tests have made it reasonably secure. The best direct distance measurements put the value of w at -0.94 ± 0.18. This value independently confirms the best result from observing baryon acoustic oscillations (the overdensity or clustering of ordinary matter at different length scales due to acoustic waves that propagated during the very early history of the universe). Astronomers gathered such observations from measurements of the temperature fluctuations in the cosmic microwave background radiation, the distribution of galaxies seen in the Sloan Digital Sky Survey, and the changes in the cosmic expansion rate over the history of the universe revealed in the Type Ia supernovae data. From observations of the baryon acoustic oscillations w = -0.98 ± 0.12.2 Both measures of the w parameter are consistent with dark energy being described by a cosmological constant.
In the case that dark energy is instead described by some kind of quintessence, the necessary fine-tuning degree is not known to the same level of accuracy as is the case for the cosmological constant. Nonetheless, it must be extremely high.
All of these recent confirmations of the biblical big bang creation model are good, but the best is yet to come. The various astronomical research teams involved in producing each of these recent verifications promise they will soon produce more precise results. This forthcoming improvement in the accuracy and trustworthiness of the measured values for the cosmic expansion rate, the geometry of the universe, the age of the universe, and the nature of dark energy will give cosmologists a much more detailed history of the universe and more exact picture of the cosmic creation event.
In turn, this superior history and picture will allow deeper and more rigorous tests of the big bang creation model. The possibility for even more evidence in favor of the Bible’s description of cosmic creation and history is tremendous. We at Reasons To Believe predict that the big bang creation model, so eloquently described by the Bible more than two thousand years ago, will pass these future measurement tests with flying colors.
|Part 1 | Part 2 | Part 3 | Part 4|
- Scriptural support for big bang cosmology and cosmic expansion: Genesis 1–3; Job 9:8; Psalm 104:4, 148:5; Ecclesiastes 1–4; Isaiah 40:22, 26, 42:5, 44:24, 45:12, 18, 48:13, 51:13; Jeremiah 10:12, 33:25, 51:15; Zechariah 12:1; John 1:3; Romans 8:20–22; Colossians 1:15–17; Hebrews 11:3; Revelation 21.
- E. Komatsu et al., “Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation,” Astrophysical Journal Supplement Series 180 (February 2009): 330–76.