Why the First Verified Detection of Gravitational Waves is HUGE News
by Fr. Robert Spitzer
Filed under Science
Now that LIGO (Laser Interferometer Gravity-wave Observatory) scientists have published their research in the scientific journal Physical Review Letters, the media is abuzz with the news of gravitational waves. It is difficult to overstate the importance of this announcement. To begin with, gravitational waves were (until now) the only major prediction of Einstein’s General Theory of Relativity that still lacked observational evidence. Because LIGO’s measurements align precisely with Einstein’s calculations, they provide further validation for his theory, which has served as the foundation of large-scale physics for a century now. Moreover, gravitational wave astronomy has vast potential to provide new and important data on black holes, galactic structure, and even the formation of the universe.
There are a number of popular articles that provide an overview of how the LIGO team detected the gravitational waves, and MIT has posted a very good video:
The key monitoring devices are two interferometers; one located in Hanford, Washington and one 1,865 miles away in Livingston, Louisiana. (Gravitational wave observatories need a distant twin to validate that local vibrations are not mistaken for actual wave signals.) Each interferometer is an extremely fine-tuned measuring devices with the ability to detect minute variations in received timing between two laser beams that travel up and back perpendicular vacuum chambers.
Because of the constancy of the speed of light, the only thing that could alter the round-trip travel time of the laser beams is an expansion or contraction of space-time itself (as Einstein predicted). In normal operations both beams complete the round-trip simultaneously, but if a gravitational wave ripples through, then the arrival times of the two laser beams will be slightly offset. To learn more about how the interferometers work, I recommend this page on the CalTech LIGO website.
In the General Theory of Relativity, the measurement and geometry of space and time vary according to the mass-energy density in a particular region. This has been verified many times but, as I mentioned above, one prediction remained to be verified—the rippling of the measure of space and time (caused by a disturbance in the space-time continuum) such as might be produced by a collision of two super dense, super massive bodies or a supernova.
In this case the disturbance was the result of a cataclysmic collision and merging of two black holes located about 1.3 billion light years from earth. The gravitational wave from this spectacular event reached the Livingston interferometer on September 14, 2015. Seven milliseconds later (traveling at the speed of light) it hit the Hanford site. Like ripples on a pond, ripples in space-time subside as they propagate, and by the time the wave reached the interferometers its frequency was extremely weak. Fortunately, the two locations had been recently upgraded to increase their level of sensitivity, and because of this were able to detect this “whisper of a wave”. The measurements at Hanford and Livingston were identical and precisely as would be predicted, giving us a remarkable confirmation of Einstein’s General Theory, as well as a penetrating look into the dynamics and structure of black holes—particularly in black hole collisions and merges.
Now that we are reasonably sure that gravitational waves exist (i.e., the rippling of the space-time continuum does occur), we may be able to get further insights into the very early conditions of the universe. One of the most significant predictions of the contemporary Big Bang model is universal inflation—a super acceleration of the space-time continuum that occurred almost immediately after the Big Bang. If such a period of inflation occurred, we would expect to detect indications of gravitational waves in the Cosmic Microwave Background (CMB) radiation (this is the ubiquitous thermal radiation left over from the Big Bang that was discovered by two Bell Labs researchers in 1964.)
One of the exciting things about LIGO’s discovery is that it gives new momentum to the search for gravitational waves in the CMB. In 2014, scientists working with the South Pole based BICEP2 telescope announced that they had made such a discovery, but later data from the Keck Array Telescope (also located at the South Pole) and the Plank satellite indicated that those readings were either partially or completely caused by the effects of intergalactic stardust. A more refined BICEP3 telescope is now operational and probing the CMB for ripples. LIGO’s confirmation of the existence of gravity waves increases confidence that scientists will be able to detect similar Big Bang induced gravity waves in the Cosmic Microwave Background radiation—which in turn will help verify initial universal inflation.
The significance of this discovery is vast indeed. Gravitational waves offer the potential to learn much more about the properties of our universe. Moreover, they may allow us to look even further back in time—to those first moments immediately after the Big Bang. We await the results of further discoveries to peek not only into the formation of super black holes and galaxies but also into the formation of our universe—and perhaps even into the advent of physical reality itself.
This article was co-written by Fr. Robert Spitzer, President of the Magis Center of Reason and Faith, and Joseph G. Miller, the Executive Director of the Magis Center.
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