Multiple General Relativity Tests Affirm a Creator

Multiple General Relativity Tests Affirm a Creator

Babe Ruth. Willie Mays. Hank Aaron. Ted Williams. This bunch would make any fan’s short list––a seemingly inevitable event this time of year––of baseball’s all-time greatest players. The arguments are obvious and compelling: they were superstars.

Looking to the stars and beyond, Christians have marshaled arguments of their own through the centuries to contend for the existence of the God of the Bible. In terms of scientific relevance, the cosmological and teleological arguments(or “causal argument” and “argument from design”) represent the two most potent lines of reasoning.

These two classical arguments have received a modern boost as the scientific community’s understanding of the theory of general relativity grows. A wealth of recently published research affirms the validity of this powerful theory and further solidifies the apologetic case for God’s existence.

When Albert Einstein first published his theory of general relativity (GR) in 1915, the proposal had no empirical foundation. While GR explained some orbital anomalies of Mercury and exhibited some philosophical elegance, real experimental validation of the theory lay decades in the future.

The first significant success for Einstein’s theory came in the late 1920s when Edwin Hubble confirmed GR’s generic prediction of an expanding universe. Over the last 80 years, extensive theoretical and observational research has supported Hubble’s original results and strongly argues that we live in a big bang universe.

Credit: Artist’s concept of general relativity experiment. courtesy NASA/JPL-Caltech.
General relativity says that massive objects product a gravitational well that deflects or bends light as it passes by.

Big bang cosmology clearly aligns with the biblical description of the universe. Both say the universe starts with a singular beginning, expands, and incorporates constant (in both time and space) physical laws that govern the cosmos. Additionally, if general relativity is correct, more recent observations imply that dark matter and dark energy comprise the dominant “stuff” of the universe. While not mentioned in the Bible, these dark substances display extraordinary design consistent with the biblical notion that one primary function of the universe is to support advanced life.

Previous precision tests had already confirmed the validity of GR but only on length scales limited to the solar system. (The generic prediction and observation of cosmic expansion does not count as a precision test.) Did general relativity accurately describe the entire cosmos? The possibility remained that GR needed modification on larger, namely galactic, scales. Scientists needed to test GR against other explanations for how objects in the universe affect one another.

Two main gravity theories that modify GR are known by the names f(R) and TeVeS (or Tensor-Vector-Scaler). Four significant research papers tested these competing theories and held the possibility of seriously challenging general relativity and, thus, big bang cosmology.

Galaxy Clusters: Discriminating Models and Affirming Dark Matter

In one paper1, a team of scientists analyzed the clustering of 70,000 galaxies extending one third of the way across the observable universe. GR, f(R), and TeVeS descriptions of gravity differ in how galaxies cluster, how gravitational lensing operates, and how quickly the structure grows. Consequently, measuring a parameter, called EG, that incorporates all three of these effects can discriminate between these models. GR predicts a value around 0.4. The paper reports a value of EG = 0.39 ± 0.06. Very consistent. In contrast, popular models of f(R) and TeVeS gravity predict values around 0.328–0.365 and 0.22, respectively.

What does this mean? TeVeS models that tweak GR to avoid postulating the existence of dark matter can be ruled out. f(R) models remain marginally consistent with the results but the next generation of surveys––by incorporating more galaxies and tightening systematic error bars––will be more decisive. Equally important, these results extend tests for GR on scales 100 billion times larger than previously measured.

Galaxy Clusters: Affirming Dark Energy

Another research team2 studied an even larger sample of galaxies—nearly 450,000. This team used large galaxy surveys and follow-up redshift measurements to assemble the most comprehensive, three dimensional tomographical map of galaxies. The redshift provided the distances to the galaxies and the gravitational lensing filled in the mass distribution of the map.

The existence of dark energy leaves tell-tale signatures that a precise galaxy map would identify. In particular, dark energy causes the universe to grow more quickly and it slows the growth of galaxy clusters. The unprecedented precision and scale of this map revealed both of these signatures. Thus, no modifications of GR are required to explain the map. Additionally, the map provides verification of the mysterious dark energy, independent of supernovae data and cosmic microwave background data.

Galaxy Cluster Simulations: No Modifications to GR

A third paper3 compared observed counts of galaxy clusters to cosmological simulations with different descriptions of gravity (specifically, GR and f(R) models). The study included the observations of the cosmic microwave background, supernovae data, measurements of the Hubble constant, and the Baryon Acoustic Oscillations to improve the constraints on modifications to GR by four orders of magnitude. Again, these results confirm the validity of GR and place serious constraints on alternative models.

X-Ray Galaxy Clusters: Further Confirmation of GR

A fourth collaboration4 described constraints placed on modifications to GR using a measurement of how the X-ray luminosity of galaxy clusters changes in time. Applying a popular growth rate characterization, GR predicts a value of 0.55 for a particular parameter designated γ. For the first time, the team placed constraints on γ using X-ray data and found concordance with GR.

These four discoveries represent a diverse set of methods, data collection/analysis and publication forums. Yet all the results affirm the validity of general relativity (particularly on cosmological scales) and the existence of dark matter and dark energy. These advances give scientists great confidence that big bang cosmology (which flows out of general relativity) accurately describes the beginning and development of the universe.

In turn, both the beginning (cosmological argument) and fine-tuning (teleological argument) evidenced by big bang cosmology testify to a powerful, caring Creator who fashioned this universe in preparation for humanity.

  1. Reinabelle Reyes et al., “Confirmation of General Relativity on Large Scales from Weak Lensing and Galaxy Velocities,” Nature 464 (March 11, 2010): 256–58.
  2. Tim Schrabback et al., “Evidence for the Accelerated Expansion of the Universe from Weak Lensing Tomography with COSMOS,” Astronomy and Astrophysics, in press.
  3. Fabian Schmidt, Alexey Vihklinin, and Wayne Hu, “Cluster Constraints on f(R) Gravity,” Physical Review D 80 (October 15, 2009): 083505.
  4. David Rapetti et al., “Constraints on Modified Gravity from the Observed X-ray Luminosity Function of Galaxy Clusters,” Monthly Notices of the Royal Astronomical Society 400 (December 2009): 699–704.