Detection of Gravity Waves

What Does the Detection of Gravity Waves Mean?

Dr. Steven Ball
Science Seminar, February 24, 2016, 7:00 pm, C101 Glaske, LeTourneau University, Longview, TX

The first detection of gravity waves coming from a binary system of two black holes merging together, from a distance of 1.3 billion light-years away, means that we have a new way to investigate the extraterrestrial universe beyond electromagnetic waves (light), which is all we have been using since the dawn of mankind. The invention of the telescope allowed us to collect, magnify and resolve light to better understand our extraterrestrial universe. That led Galileo over 400 years ago to some surprise findings, completely at odds with traditional understanding of the heavens. We may be primed for a somewhat similar revolution today, since all of our knowledge of the heavens beyond the few spacecraft we have sent to nearby worlds, has depended only on the faint sources of light reaching us. In fact, we couldn't even see the merging black holes that caused the gravity waves LIGO detected. They were too far away and didn't give off visible light anyway. But we know the waves were caused by merging black holes because of the shape of the signal we received matches exactly that predicted from using general relativity. This is quite a remarkable accomplishment, especially considering the stretching of space was only on the order of 1/1000 the size of a proton. Both the Livingston and Hanford detectors each saw the signal, one just 7 milliseconds before the other, allowing us to roughly locate the black hole merger. We actually need a third LIGO detector to do that precisely, which we soon will have with the LIGO India detector. From the frequency of the signals we can even determine the sizes of the black holes, both over 30 solar masses, and we can estimate that the power emitted during 20 milliseconds was greater than all the stars in the visible universe combined, and it took 3 solar masses of energy and converted it into gravitational waves. The resulting large black hole is 3 solar masses lighter than the sum of the two separate black holes that merged together.

This is all quite remarkable, but not revolutionary. It is entirely consistent with general relativity, a 100 year old development in physics, so nothing new theoretically is gained by this observation. In fact, observing extreme field effects in binary pulsars provided the first method to stringently test general relativity, since its predictions grow vastly different from Newtonian gravity in such extremes. However, these extreme fields are still the domain of general relativity, where a smooth, continuous space-time curvature is necessary for its validity. It works wonderfully in the macroscopic world. Go into the microscopic limit of the quantum world and quantum fluctuations destroy this condition, and demand that we bridge quantum mechanics with relativity via a theory of quantum gravity, something string theory proposes, but has thus far received no experimental validation. What we hope to eventually learn as we begin studying more of these extreme astrophysical events is how to understand the connection between general relativity and quantum theory. Once we do, we may be able to go further back towards the beginning of the universe itself and understand how the 4 fundamental forces split up into the low energy world we live in today. But even then, it would not really answer the ultimate questions of first causality. A Christian need not feel threatened by this, since none of this really explains how we get something from nothing. That, the author of Hebrews 11 explains well, requires faith.