New sophisticated measurements of radio waves from two heavy stars have provided weighty evidence for understanding how the universe began. An international team of astronomers has achieved the most definitive set of tests to date of Einstein’s theory of general relativity (GR) and, by extension, the biblical doctrine of cosmic creation. Insofar as GR describes the theory of gravity and, thus, features of the universe’s space-time fabric, it is consistent with a cosmic creation model.
The team of 29 researchers led by Michael Kramer of the Max Planck Institute for Radio Astronomy published the results of their 16-year study of the orbital changes in the pulsar system PSR J0737-3039A/B.1 This system is the only known case of two active pulsars orbiting one another. A pulsar is a neutron star that produces regular pulsating radio emissions as a result of possessing a strong magnetic field. Pulsars spin extremely fast and emit powerful beams of light that “pulse” into our view, similar to the way we see beams of light from a lighthouse.
The two pulsars (a two-star system is known as a binary) in the PSR J0737-3039 system, A and B, have rotation rates of 22.70 and 2.77 milliseconds, respectively. Therefore, radio astronomers observe 44 and 361 pulses of radiation every second from A and B, respectively.
The present orbital period of B about A is just 2.454 hours. This orbital period is the shortest yet known for pulsars with a binary companion. It is a factor of three times shorter than the pulsar-neutron star system PSR B1913+16, which delivered the previous best test of Einstein’s theory of general relativity, a measurement for which physicists Joseph Taylor and Russell Hulse were awarded the 1993 Nobel prize in Physics.
The Double Pulsar
The two neutron stars in the PSR J0737-3039 system have masses of 1.338 and 1.249 times the Sun’s mass. The diameters of these stars are about 116,000 times smaller than the Sun’s. Their densities exceed 2 billion tons per teaspoonful!
This binary system’s orbital eccentricity is 0.088 (for comparison Earth’s orbital eccentricity = 0.0167). The rotational stability (pulsing frequency) of the two neutron stars is comparable to the best atomic clocks. Previous long-term studies of other pulsars’ extremely tiny departures from rotational stability reveal that neutron stars possess a solid crust of neutrons and a liquid interior of neutrons.
Gravitational theories are best tested where one or two neutron stars are in a binary system. The best such candidates are where two neutron stars orbit one another and where both neutron stars are pulsars. Better yet is when the two pulsars have a short orbital period, a nonzero orbital eccentricity, and orbital planes closely aligned to our line of sight. It is remarkable, and some would say a gift from God, that the only known binary pulsar manifests all these optimal features for testing theories of gravity.
To measure the pulses from the PSR J0737-3039 system, Kramer’s team used six of the largest radio telescopes (the Robert C. Byrd Green Bank Telescope, the Effelsberg 100-m Radio Telescope, the Jodrell Bank Observatory, the Nançay Radio Observatory, the Westerbork Synthesis Radio Telescope, and the Parkes radio telescope) plus the Very Long Baseline Array (VLBA). The VLBA consists of ten 25-meter radio telescopes stretching from Hawaii to the Virgin Islands that are linked together as an interferometer. The VLBA was crucial for determining an accurate direct distance measurement to the PSR J0737-3039 system, without which precision tests of GR would not have been possible. Measurements from the seven telescope systems provided seven different tests.
Kramer’s team was patient. They continued observing the PSR J0737-3039 pulsars month after month, year after year, without publishing any results. Even when the LIGO and Virgo Collaborations published their direct detections of the gravity waves predicted by GR from the mergers of black holes and neutron stars,2 Kramer’s team stood pat. They waited until they accumulated enough measurements to determine the energy carried away by gravitational waves to 1,000 times greater precision than anything achieved by the LIGO and Virgo gravitational wave telescopes.
Background to the Tests
GR has passed every experimental and observational test that astronomers and physicists have devised to date. I described these tests in The Creator and the Cosmos, 4th edition.3 The tests left no doubt that GR is the final answer in describing gravity. There is one regime (natural phenomenon), however, where a possibility existed that an alternate theory of gravity may substantially contribute. That regime is the extremely strong gravitational fields that exist near neutron stars and black holes. The gravitational field on the surface of a typical neutron star is about 200 billion times that at Earth’s surface. Hence, a 200-pound man on Earth would weigh 20 billion tons on a neutron star!
What the Tests Accomplished
The patience of Kramer’s team paid off. Their observations yielded the most wide-ranging and precise tests of GR for strong gravitational field regimes. Through observing the reductions in the neutron stars’ masses, size of their orbit, and tiny variations in the timing of their pulses, Kramer and his colleagues achieved seven distinct tests of GR.
Two of the seven tests had never been performed. For example, Kramer’s team showed how photons from one of the neutron stars slowed down and their directional path bent as they passed through the intense gravitational field of the other neutron star. The effects they observed fit what GR predicted. Another first-time test was the demonstration of the manner in which gravity distorted the shape of the neutron stars’ orbit—again, just as GR predicted.
The results of the seven tests expressed as observations compared to GR predictions are as follows:4
|GR Test||Comparison with GR Prediction Where GR = 1.0|
|Shapiro delay shape||1.00009 ± 0.00018|
|Shapiro delay range||1.0016 ± 0.0034|
|time dilation||1.00012 ± 0.00025|
|periastron advance||1.000015 ± 0.000026|
|gravitational wave emission||0.999963 ± 0.000063|
|orbital deformation||1.3 ± 0.13|
|spin precession||0.94 ± 0.13|
Shapiro delay is named after Irwin Shapiro, who made the first high-precision tests of GR in the 1970s.5 We were on the research staff at Caltech at the same time, and I enjoyed several conversations with him about GR tests and their implications.
The results of these seven tests come from 16.2 years of observing the PSR J0737-3039 system. The results will inevitably improve with more observing time. (The measuring errors are reduced by the square root of the observing time. For example, four years of measurements compared to just one year of measurements reduces the measuring error by a factor of two.) Dramatic improvements are expected in just 10–20 years. Within a decade, improved measurements of the orbital deformation of the pulsars’ spin precessions will yield the values of the neutron stars’ diameters.
Physical and Philosophical Implications
The values of the neutron stars’ diameters will enable astronomers to understand the behavior of the densely packed neutrons in their interiors. This knowledge will yield improved refinements and insights into particle creation models.
The team’s published results have already yielded new insights about the properties of the interstellar medium between PSR J0737-3039 and Earth, and future observations will produce several more insights. Future observations also promise to deliver more comprehensive and detailed models for the formation of double pulsar systems and the likelihood of discovering one or more of these systems.
The most exciting outcome from the researchers’ results is that GR now stands as, by far, the most exhaustively tested and affirmed principle in physics. GR has now been affirmed under all gravitational field regimes.
This affirmation should be good news for all theists and especially Christians. The space-time theorems have proved that the universe has a beginning. That beginning includes the beginning of space and time and is based on the assumptions that the universe contains mass and that GR reliably describes the dynamics of massive bodies in the universe. Thanks to how exhaustively GR has been tested and shown to pass all tests with flying colors, we can be extremely confident that the universe has a beginning and that a Causal Agent beyond space and time created our universe of matter, energy, space, and time just as the Bible declared thousands of years ago.6
1. Michael Kramer et al., “Strong-Field Gravity Tests with the Double Pulsar,” Physical Review X 11, no. 4 (December 13, 2021): id. 041050, doi:10.1103/PhysRevX.11.041050.
2. B. P. Abbott et al., “Astrophysical Implications of the Binary Black Hole Merger GW150914,” Astrophysical Journal Letters 818, no. 2 (February 20, 2016): id. L22, doi:10.3847/2041-8205/818/2/L22; Hugh Ross, “How Gravitational Waves Help Explain the Universe’s Beginning,” Today’s New Reason to Believe (blog), Reasons to Believe, March 10, 2016.
3. Hugh Ross, The Creator and the Cosmos, 4th edition (Covina, CA: RTB Press, 2018), 114–120.
4. Kramer et al., “Strong-Field Gravity Tests,” 37.
5. Irwin I. Shapiro, “Fourth Test of General Relativity,” Physical Review Letters 13, no. 26 (December 28, 1964): 789–791, doi:10.1103/PhysRevLett.13.789.
6. Hugh Ross with John Rea, “Big Bang—The Bible Taught It First!,” Reasons to Believe (July 1, 2000); Hugh Ross, “Does the Bible Teach Big Bang Cosmology?” Today’s New Reason to Believe (blog), Reasons to Believe, August 26, 2019.