On September 14, 2015, at 09:50:45 UTC gravitational waves emitting from the collision of two black holes were identified at the Laser Interferometer Gravitational Wave Observatory, exciting and perplexing observational astrophysicists and the general population alike. This sample science essay explores the direct observation of gravitational waves.
Overview of Gravitational Waves
Astronomers and scientists have debated the existence and nature of gravitational waves since Galileo and Darwin challenged the scientific community’s view on space and the universe. The American Physical Association has summarized the concept of gravitational waves in the following way:
“Gravitational waves are signals from distant objects in the universe that can travel vast distances. Unlike light waves, gravitational waves are not blocked or altered by interactions with matter in the universe” (paragraph 2).
The idea that gravity is contained in waves implies that the force of gravity travels across timespace after it is exerted by a given object of matter. Moreover, if gravitational waves can be said to move in this way, then this means that there must also exist an upper limit on the velocity at which they can move – the speed of light.
According to the modern scientific view of the universe, no object within the universe can travel at a speed greater than that of light; and insofar as gravity moves in waves, gravity itself would also be subject to this limit.
Theoretical status of gravity and time
This theoretical understanding of gravity is, of course, different from how one might ordinarily think of gravity on the basis of common sense. The common sense understanding is encapsulated, of course, in the classic story of Newton inventing the concept of gravity after getting hit by a falling apple on his head, in an older age of science.
When considering objects exerting gravity, what can be said is that objects that are closer to each other tend to exert a greater effect on each other than objects that are farther away, and that larger objects exert a greater effect than smaller ones (Carroll). Here, however, what is under consideration is the gravity itself, as such, and not the objects per se.
This is conceptually a little difficult to imagine at first, insofar gravity moves directly across the medium of spacetime itself, and not really within the context of some pre-existing spacetime. This is similar to the idea that spacetime itself is “curved” in some way: this is difficult to imagine, for the simple reason that when people normally think about curvatures, they think of objects within spacetime (a winding road, for example) and not the very structure of spacetime itself.
Proving the existence of gravitational waves
Scientists have long sought to empirically prove the existence of gravitational waves. The main significance of gravitational waves has to do with questions regarding cosmology, and the light that such waves would be able to shed on such questions. As Lewis has put it, the discovery of gravitational waves “would provide strong evidence that the universe expanded in an extremely rapid burst right after it was born, a process known as cosmic inflation.
But the discovery also offers insight into fundamental physics, including, perhaps, the idea that, at one point, most or all of the forces of nature were unified into a single force” (paragraph 2). In short, the hope among scientists has been that the existence of gravitational waves would contribute to a deeper understanding not just of the nature of gravity but also of the very nature of spacetime reality itself.
Description of the gravitational wave discovery
Recently, scientists did in fact succeed at empirically observing gravitational waves. Perhaps it is worth clarifying what exactly is meant by this statement. Extremely sophisticated and expensive technology was needed in order to make this discovery possible. As Twilley has written, one of the lead researchers on the project was viewing a data monitor, when:
“the waves appeared on his screen as a compressed squiggle, but the most exquisite ears in the universe, attuned to vibrations of less than a trillionth of an inch, would have heard what astronomers call a chirp—a faint whooping from low to high” (paragraph 2).
The facility where the relevant equipment is held is called LIGO, and it can be found in the states of Louisiana and Washington. That is, the facility consists of huge concrete pipes in both of these locations, with the basic idea that gravitational waves can be detected when the pass from one of the “arms” of the facility to the other.
Einstein’s theories proven
The blip on the computer screen mentioned above was a record of one such detection of gravitational waves actually occurring, and this is what is meant when it is said that scientists have now directly observed gravitational waves. The huge size of LIGO was necessary in order to produce the level of sensitivity that would be needed in order for the equipment to actually register the presence of gravitational waves.
At first, even the scientists themselves barely believed what they had seen. Twilley has quoted one of the scientists as having stated the following:
“We’re saying that we made a measurement that is about a thousandth the diameter of a proton, that tells us about two black holes that emerged over a billion years ago. . . . That is a pretty extraordinary claim and needs extraordinary evidence” (paragraph 4).
By now, however, the evidence has been confirmed with a great degree of certainty, and it has become safe for the scientists involved in the project to actually make this claim. The main idea is that the discovery of gravitational waves confirms theoretical speculation that the universe as it is presently known was produced by the almost-religious collision of two black holes—a collision that released an almost unfathomable amount of energy in the form of gravitational waves and fundamentally changed the very structure of spacetime itself.
The recent discovery of gravitational waves was several years in the making. When one attempts to perform cursory research on this subject, one comes across several different reports that conflict with each other in a rather confusing way; it becomes important to check the dates on the various reports.
Implications of gravitaional waves and the future of science
Some commentators have suggested that the discovery of gravitational waves can be understood as opening up a new era for science as a whole. As Francis has pointed out, “this is just the beginning. The similarly-sized Virgo observatory in Europe—undergoing a similar upgrade as LIGO—and the KAGRA experiment (still in the planning stages) in Japan will provide two more observatories to form a global gravitational-wave network.
And plans are in the works for a space-based detector that could ‘hear’ frequencies that LIGO and other Earth-based observatories can’t” (paragraph 16). With the discovery of gravitational waves by the scientists at LIGO, it is now likely far more that these projects will, in fact, receive adequate funding to move forward and meet with success.
More broadly, the discovery of gravitational waves has enormous implications for people’s understanding of the basic nature and structure of spacetime reality itself. Again, according to Einstein’s theory, all gravitational waves are emanations of an original collision between two black holes that produced the universe as it is currently known and curvatures in the structure of spacetime that are still felt to this day.
If scientists can actually detect these waves—which they now have—then they can also engage in much more sophisticated speculations regarding what really happened at the very beginning of the universe itself. Aside from being intrinsically fascinating in its own right, such insight could open up radically new possibilities for scientists’ basic understanding of the constitution of reality.
At the present time, for example, there is still an ongoing conflict between Einstein’s general theory of relativity on the one hand and the insights produced by the branch of physics known as quantum mechanics on the other. This is one of the most important problems currently facing modern science, and the discovery of gravitational waves could potentially open doors toward its final resolution:
“Someday, the very notions of space, time, and locality may turn out to be emergent, just as water waves emerge from the molecules below” (paragraph 18).
If gravity is not an instantaneous effect but rather the product of waves moving through the structure of spacetime, and if these waves can now actually be detected by scientists, then it may become possible to make important inductions and deductions regarding the fundamental nature of spacetime itself, and thereby work toward a deeper theory of reality that can reconcile the current split between the general theory of relativity and quantum mechanics. In short, then, the fact that gravitational waves have now been perceived can only be called an exciting event.
American Physical Society. “Gravitational Waves.” 2016. Web. 28 Feb. 2016.
Carroll, Sean. “All Physics Is Local.” The Atlantic. 12 Feb. 2016. Web. 28 Feb. 2016.
Francis, Matthew. “The Dawn of a New Era in Science.” The Atlantic. 11 Feb. 2016. Web. 28 Feb. 2016
Lewis, Tanya. “What Gravitational Ripples from Big Bang Mean for Physics.” Live Science. 18 Mar 2014. Web. 28 Feb. 2016.
Moskowitz, Clara. “Gravity Waves from Big Bang Discovered.” Scientific American. 17 Mar. 2014. Web. 1 Mar. 2016.
Overbey, Dennis. “Gravitational Waves Detected, Confirming Einstein’s Theory.” New York Times. 11 Feb. 2016. Web. 28 Feb. 2016.
Twilley, Nicola. “Gravitational Waves Exist: The Inside Story of How Scientists Finally Found Them.” New Yorker. 11 Feb. 2016. Web. 28 Feb. 2016.