On Thursday, February 11, 2016, the physics and astronomy community were abuzz with the announcement of the first direct detection of gravity waves. Albert Einstein had predicted the existence of gravity waves a century ago. Gravity waves are a part of Einstein’s general theory of relativity, a theory that revolutionized physics. General relativity united space and time into a single entity, what physicists call space-time. Space-time is a substance, sort of like a fabric. Unlike classical, or Newtonian, physics, in which space and time are mere backdrops where the real players, matter and energy, acted out their roles, with general relativity, space-time is an active participant interacting with matter and energy. General relativity relates how gravity and other forces of nature interact with space-time. Einstein realized that, according to his theory, gravity ought to produce very small waves, or ripples, in space-time. Over the years, the predictions of general relativity have been tested repeatedly, and it is one of the best-supported theories in the history of science.
However, gravity waves were one prediction of Einstein’s theory that had not been tested, at least not directly. The problem is that gravity waves are expected to be very feeble. To improve the odds of detection, it helps to be close to a very strong source of gravity waves. However, we don’t happen to live close to any of those. Furthermore, those environments aren’t the most safe places to be, as we soon shall see.
The orbital behavior that Hulse and Taylor found . . . matched the predictions of general relativity.
In 1974, Russell Hulse and Joseph Taylor were the first to detect gravitational waves, albeit indirectly. They studied PSR B1913+16, a binary system consisting of two neutron stars in a close orbit around one another. Neutron stars are very dense bodies, having perhaps two or three times the mass of the sun, but are only a few miles in diameter. By comparison, the sun is nearly a million miles across. Because they are so small, neutron stars in a binary system such as PSR B1913+16 can orbit one another very closely, making the gravitational attraction between them immense. Physicists expected that the tremendous gravity would produce gravitational radiation (waves in space-time) that would carry away orbital energy, causing the orbit to shrink. The orbital behavior that Hulse and Taylor found in PSR B1913+16 matched the predictions of general relativity. In 1993, Hulse and Taylor received the Nobel Prize in Physics for their work. Additional studies further confirmed this work.
The indirect detection of gravity waves was important, but direct detection would be better. More than two decades ago, a team of scientists began construction of the Laser Interferometer Gravitational-Wave Observatory (LIGO) to do this. LIGO consists of twin systems, one near Livingston, Louisiana, and the other on the Hanford Site in the State of Washington. Either system consists of two perpendicular tunnels four kilometers long. Laser beams travel back and forth along the two tunnels, and the light eventually is combined and compared in a sensitive interferometer. A gravitational ripple would show up as a vibration in the LIGO devices. During a decade of service, LIGO detected many events, but all of them were the result of local events, such as small earthquakes or even the fall of a tree nearby. However, these events would show up on one detector but not the other.
This changed last September, when both LIGO detectors picked up the same signal in an event that lasted about a quarter of a second. The only difference in the two detections was that they were seven milliseconds apart in time. That meant that the event recorded was outside of the Earth, and the time delay helped determine the direction in space where the ripple came from. The detection was not announced publicly for five months, to allow time to analyze the data properly. Scientists now call this detection GW150914 (the GW refers to gravity wave, and the numbers refer to the date of detection, September 14, 2015).
The duration and the frequency spectrum of GW150914 allow astrophysicists to model the event that caused it. The best model is that there were two black holes in a very close binary orbit, one black hole with twenty-nine times the mass of the sun, and the other thirty-six times the mass of the sun. As with PSR B1913+16, the binary neutron star system that Hulse and Taylor used indirectly to confirm gravity waves, the two black holes in this system would have lost orbital energy as they produced gravitational waves. Eventually, the orbits of the black holes decayed so much that the two collided and merged into a single black hole, having a mass of about sixty-two times that of the sun. This was a very violent event, which converted about three times the mass of the sun into gravity waves via Einstein’s famous E = mc2 equation. It was these waves that LIGO detected. Additional information gleaned from the data yielded a redshift for the waves that correspond to a distance of about 1.3 billion light-years for the black hole merger.
This first direct confirmation of gravitational waves is just another example of how far out and cool God’s creation can be.
What does this mean to the creation model? Not much. Some creationists may wonder about the distance, but we already know about many objects even farther away. Creationists are well aware of the light-travel-time problem, and we have proposed several solutions. By the way, the big bang has its own light-travel-time problem, the horizon problem. Others may wonder about the modeling that went into this. As an astronomer and physicist who happens to be a biblical creationist, I don’t see a problem with this. There is good evidence that black holes exist. Contrary to what a few creationists seem to think, black holes were not made up to salvage evolutionary ideas. God probably made neutron stars and black holes on Day Four, along with the other astronomical bodies. This first direct confirmation of gravitational waves is just another example of how far out and cool God’s creation can be.