Quantum Gravity Constraints Affirm Cosmic Creator

One of the cornerstone beliefs of the Christian faith is that the universe had a beginning, which implies a cosmic Beginner. Physical scientists who are opposed to Christianity will admit that overwhelming observational evidence affirms that the universe had a beginning, but they point out that astronomers lack absolute proof of a cosmic beginning. There is room to speculate, they claim, in the part of the universe where observations are lacking. I’ll present the technical details—especially a series of quantum gravity tests—on what the latest research shows. But first I’ll explain how the search for a beginning galvanized my life and career at a young age.

Personal Quest
I was not raised in a Christian home, but since age seven I was intensely curious about the universe. By my mid-teens I recognized that if the universe had a beginning, that beginning would have profound philosophical and theological implications. That recognition led me to investigate the world’s major religions. My spiritual journey during my late teens culminated in an 18-month-long study of a Bible given to me by the Gideons. I clearly remember the night when, at 1:06 AM, I signed my name in the back of that Gideon Bible, committing my life to Jesus Christ as my personal Lord and Savior.

A major factor in committing my life to Christ was the mounting evidence for the big bang model and the Bible’s declaration that the universe had a beginning, one that included the creation of all matter, energy, space, and time. I was eager to see if the evidence for a cosmic beginning would continue to mount. 

Within weeks after that life-altering night, I was allowed to join the American Astronomical Society thanks to a written recommendation from Princeton physicist Robert Dicke. Included in my membership was a subscription to the Astrophysical Journal

One of the first issues I received included a short paper by Arno Penzias and Robert Wilson announcing their discovery of a pervasive 3K cosmic background radiation.1 Accompanying this paper was one by Robert Dicke and his team of graduate students that explained what Penzias and Wilson had discovered.2 Dicke’s team pointed out that the pervasive radiation discovered by Penzias and Wilson was the radiation left over from the cosmic creation event. Here was the additional evidence for a cosmic beginning I was hoping to see. There was much more to come.

Space-Time Theorems 
Soon after Penzias and Wilson’s discovery, physicists in Britain and South Africa began a study on the physics of space and time. In 1970, physicists Stephen Hawking and Roger Penrose published the first of the cosmic space-time theorems.3 They showed that the cosmic beginning is not just a beginning of matter and energy but also of space and time, just as the Bible declared thousands of years ago in, for example, 2 Timothy 1:9; Titus 1:2, and Hebrews 11:3.

Since 1970, physicists have produced over thirty space-time theorems. The most famous one is the Borde-Guth-Vilenkin theorem.4 Arvind Borde, Alan Guth, and Alexander Vilenkin demonstrated that, regardless of the homogeneity, isotropy, and energy conditions of the universe, the universe must be subject to an initial space-time singularity. Two years later, Vilenkin wrote in his book Many Worlds in One, “With the proof now in place, cosmologists can no longer hide behind the possibility of a past eternal universe. There is no escape, they have to face the problem of a cosmic beginning.”5

Quantum Gravity   
Physicist Sean Carroll disputes the claim that there is no escaping a cosmic beginning. He points out that the proof of a cosmic beginning is based on what we know about the past 99.9999999999999999999999999999999999999999999999999999999999% of the universe’s history. Carroll claims that previous to 10-43 seconds after the cosmic origin event (the quantum gravity era where quantum mechanics may compete with gravity in determining the dynamics of the universe), a possibility exists for quantum space-time fluctuations or foam to have been sufficiently large to permit an escape from an initial space-time singularity.6

Quantum Gravity Tests
Carroll’s claim about a conceivable escape from a space-time beginning rests on the incapability of astronomers and physicists to perform experiments or make measurements about the state of the universe during that extremely brief quantum gravity era. To produce the energy conditions that existed during the quantum gravity era, physicists would need to construct a particle accelerator with an acceleration path length a billion trillion times longer than the CERN Large Hadron Collider’s 27 kilometers (17 miles). It would stretch from Earth out to the most distant quasars! Physicists and astronomers may dream of directly probing the quantum gravity era, but the possibility of the world’s governments funding a 12-billion-light-year-long particle accelerator anytime soon is remote.

The impracticality of constructing a particle accelerator that stretches out to the most distant quasars does not mean there is no hope for probing quantum gravity physics. What happens in the quantum gravity era does not always stay in the quantum gravity era. It leaks out. 

blurred quasar images: Quantum space-time fluctuations during the first tiny split second of the universe’s 13.8-billion-year existence accumulate or grow over light travel paths. That is, they become “frothier” over long pathways through space. Such an accumulation would blur the images of distantly observed quasars and blazars in proportion to the sizes of the quantum space-time fluctuations existing during the quantum gravity era. (A blazar is a quasar where the relativistic jet of ionized matter generated outside the event horizon of the quasar’s supermassive black hole is pointed directly or nearly directly at Earth.) The longer the distance, the greater the degree of blurring. The shorter the wavelength of observation, the greater the degree of blurring. 

So far, observations at visual and ultraviolet wavelengths by the Hubble Space Telescope fail to detect any blurring of distant quasar images.7 In 2015, a team of six astronomers led by Eric Perlman used x-ray observations of quasars from the Chandra X-Ray Space Telescope to establish tighter constraints on quantum gravity speculations.8 They also demonstrated how observations of quasars at gamma-ray wavelengths with the Fermi Gamma-ray Space Telescope and ground-based Cerenkov telescopes could constrain quantum gravity speculations to a much greater degree.

deviations from Lorentz invariance: Lorentz invariance (aka Lorentz symmetry) is the proposition that the laws of physics are the same for all observers in the universe. Many quantum gravity models, in particular models with large quantum space-time fluctuations and Loop Quantum Gravity models, predict that Lorentz invariance will be violated at high energy scales, higher than the Planck energy of 1.22 x 1019 GeV (1 GeV = 1 billion electron volts or 1.602 x 10-10joules), and that tiny deviations from Lorentz invariance will occur at lower energy scales. Observations with the Fermi Space Telescope of an intense gamma-ray flare from the blazar PKS 2155-304, 1.5 billion light-years away, established that there was no violation of Lorentz invariance for energy levels less than 2.1 x 1018 GeV, assuming a linear dependence on photon speed with energy, and less than 6.4 x 1010 GeV, assuming a quadratic dependence on photon speed with energy.9

In 2018, a team of eight astronomers led by Carlo Romoli published their analysis of an extremely bright gamma-ray flare emission from the blazar 3C 279 (see figure 1).10 Romoli’s team achieved quantum gravity limits nearly as stringent as those derived from PKS 2155-304’s gamma-ray flare. They determined that no violation of Lorentz invariance occurred for energy levels less than 1.7 x 1017 GeV, assuming a linear dependence on photon speed with energy, and less than 2.0 x 1010 GeV, assuming a quadratic dependence on photon speed with energy.

Figure 1: Blazar 3C 279 Imaged at Gamma-Ray Wavelengths by the Compton Observatory
Credit: NASA

In 2021, four astronomers led by Qi-Qi Zhou used 37 groups of multiwavelength polarization measurements collected from five blazars, spanning a distance range from 1.5 to 4.7 billion light-years, to establish stringent constraints on possible Lorentz invariance violations.11 If Lorentz invariance is violated, the group velocities of left- and right-handed circularly polarized photons that are emitted from the same astrophysical source should differ slightly, leading to vacuum birefringence. Zhou’s team used the polarization measurements from the five blazars to calculate the birefringence parameter, h. If there is no Lorentz invariance violation at all, then h = 0.  Zhou and his colleagues established at a 95% confidence level that h must be less than 8.91 x 10-7 (or 0.000000891).

Physicists Fabian Kislat and Henric Krawczynski analyzed optical polarization data from 72 active galactic nuclei and gamma-ray bursts to establish an exceptionally stringent limit on a large category of quantum gravity models.12 Their analysis established a lower limit on the energy scale of quantum gravity that is a million times higher than the Planck energy, “severely limiting the phase space for any [quantum gravity] theory that predicts a rotation of the photon polarization quadratic in energy.”13

Other quantum gravity models predict that at energy levels far below the Planck energy the propagation speed of very-high-energy gamma rays will deviate from the velocity of light. Specifically, photons of different energies emitted simultaneously from a source in a distant galaxy would arrive at different times. The Major Atmospheric Gamma Imaging Cherenkov (MAGIC) Collaboration measured the arrival times of the most energetic photons ever detected, those from the 25-second gamma-ray burst event GRB 190114C (see figure 2), in a galaxy 4.5 billion light-years away. It determined that any departure from the velocity of light by GRB 190114C’s gamma rays must be less than 1.7 x 10-17 (again, a very tiny number).14  

Figure 2: Hubble Space Telescope Image of the GRB 190114C’s Afterglow
The blue colors beyond the core signal reveal the presence of hot, young stars, indicating that GRB 101114C’s host galaxy likely is a large spiral galaxy. Credit: NASA

Four other astrophysicists used spectral lag data from the Burst and Transient Source Experiment (BATSE) satellite to analyze multiple gamma-ray burst events from multiple distant galaxies.15 They established that, at a 95% confidence level, there was no violation of Lorentz invariance for energy levels less than 3.7 x 1018 GeV, again assuming a linear dependence on photon speed with energy. They also point out that detecting gamma-ray burst events with energies greater than 100 GeV will become routine in the near future, which will enable direct tests of Lorentz invariance at energy levels greater than the Planck energy. While not yet routine and frequent, the High Energy Stereoscopic System (H.E.S.S.), MAGIC, and Very Energetic Radiation Imaging Telescope Array System (VERITAS) experiments have detected gamma rays at energy levels from 200 to 500 GeV from MAXI J1820+070, an x-ray binary star where one member is a black hole.16   

Already, however, astrophysicists have achieved a definitive test at energies above the Planck energy. A team of nine astrophysicists led by Vlasios Vasileiou analyzed emission from four bright gamma-ray bursts observed by the Fermi Space Telescope.17 The team determined that, at a 95% confidence level, there was no violation of Lorentz invariance for energy levels less than 7.6 times the Planck energy, again assuming a linear dependence on photon speed with energy. In a subsequent article, Vasileiou and his colleagues declared, “Our results set a benchmark constraint to be reckoned with by any QG [quantum gravity] model that features spacetime quantization.”18

The most recent effort is by a team of 18 astrophysicists undertaking a project to gather the biggest sample of gamma-ray sources in distant galaxies from the H.E.S.S., MAGIC, and VERITAS collaborations to yield the most stringent constraint on the quantum gravity energy scale. So far, they have developed all the statistical methods they need for processing the data and have optimized their methods through computer simulations.19 In a forthcoming paper, they will publish their quantum gravity constraints.

black hole properties: Different quantum gravity models affect the properties of black holes in distinct ways. For example, physicists Carlo Rovelli and Francesca Vidotto demonstrated that if primordial black holes exist, they could produce strong signals, detectable by current gamma-ray telescopes, that would reveal the nature of quantum gravity physics.20 (Primordial black holes are hypothetical black holes that formed soon after the big bang, when the density of matter was so great that black holes of much less mass than stellar black holes may have formed and, thus, could evaporate in less time than the age of the universe.) Physicists Carlos Barceló, Raúl Carballo-Rubio, and Luis J. Garay showed that certain quantum gravity models predict echoes in the ringdown of gravitational waves from black hole merger events that would be detectable by currently existing gravity wave telescopes.21

Physicists Hal Haggard and Carlo Rovelli calculated where, relative to the event horizons of supermassive black holes, nonperturbative quantum gravity phenomena would be maximally detectable by the Event Horizon Telescope (EHT), a global array of millimeter-wave radio telescopes stretching from Asia to Hawaii to Germany and from the South Pole to Greenland.22 In 2013, physicist Steven Giddings explained how—in some quantum gravity models—quantum space-time fluctuations could distort or suppress the photon ring or the edge of the shadow of supermassive black holes.23 In 2023, physicists Arundhati Dasgupta and José Fajardo-Montenegro demonstrated additional ways observable effects of certain quantum gravity models could be detected or constrained by the EHT.24 While the initial image of the supermassive black hole at the Milky Way Galaxy’s center produced by the EHT (see figure 3) is not yet detailed enough to test quantum gravity models, future images from the EHT may well be. 

Figure 3: Initial Event Horizon Telescope Image of the Milky Way Galaxy’s Supermassive Black Hole
The dark core shows the event horizon, within which no light can escape the black hole’s gravity. The bright ring exterior to the event horizon is where matter being drawn into the black hole is being converted into energy with 10–42% efficiency. Credit: EHT Collaboration      

nano-diamonds: In 2021, a team of ten physicists led by Yair Margalit successfully built and demonstrated the operation of a Stern-Gerlach effect interferometer for experiments on single atoms.25 In 2023, two Israeli physicists demonstrated how a Stern-Gerlach interferometer could be used to levitate and manipulate nano-diamonds in a weak magnetic field.26 Nano-diamonds are diamonds with diameters between a billionth and a ten-millionth of a meter. The number of individual carbon atoms in nano-diamonds would range from a few hundred to several thousand. The two physicists showed how accurate measurements of rotations of nano-diamonds in a Stern-Gerlach interferomenter could yield fundamental tests or constraints on quantum gravity models. 

Cosmic Creation Implications
Without exception, all observations relevant to the quantum gravity era that have been performed to date sustain a space-time beginning to the universe. The diverse quantum gravity tests that astronomers have achieved demonstrate that the more scientists learn about the universe, the more scientific evidence they accumulate that a God beyond space and time created the universe of matter, energy, space, and time. One hundred percent of the empirical evidence sustains a cosmic beginning in all the detail that the Bible declared thousands of years ago.

Have astronomers eliminated all possible speculations about a no-beginning universe? No. To do so would require that they possess exhaustively complete knowledge about every feature of the universe. Since astronomers are constrained in their observations and experiments to the cosmic space-time dimensions and the laws of physics, they can never accumulate complete knowledge about the universe. What they can do is progressively squeeze atheistic speculations about the universe into a smaller and smaller corner of possible speculation. Thanks to the quantum gravity tests accomplished by twenty-first century astronomers, the remaining corner of atheistic speculation is now mindbendingly tiny. By contrast, these tests provide progressively stronger scientific evidence for a cosmic beginning consistent with the biblical texts.  


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