Cook 1 Kelly Cook Dr. Gan PHY 335 15 November 2017 LIGO and its Role in the Detection of Gravitational Waves Abstract On October third of this year, the Nobel Prize in physics was awarded to three scientists by the names of Rainer Weiss, Kip Thorne, and Barry Barish for the direct detection of gravitational waves, which are scientific phenomena that have evaded technology for decades. With the help of the Laser Interferometer Gravitational-Wave Observatory, otherwise known as LIGO, modern science has finally developed a piece of technology advanced enough to pick up gravitational waves. Gravitational Waves and the Origins of LIGO Due to Einstein s predictions in his theory of general relativity, the existence of gravitational waves is nothing new. In fact, science has made many attempts to find a way to detect them. However, due to an advancement in technology, the Laser Interferometer Gravitational-Wave Observatory (LIGO) is capable of detecting gravitational waves. In short, gravitational waves are most often described as ripples in spacetime (Chang). When an event occurs in space, such as two black holes colliding, that event creates creases in the very fabric of space-time, which, of course, are called gravitational waves. They are everywhere, but they are not visible to the human eye. Because the existence of gravitational waves has been known
Cook 2 for quite some time now, that leads to the following question: What makes them so difficult to detect in the first place? There are many different ways gravitational waves could be created. If a star collapses, pulsations and instabilities encountered by the collapsing star will also produce GWs (Fryer). When a phenomenon like this occurs in space, and the ripples that are gravitational waves are radiated, it takes them quite a bit of time to reach Earth. By the time a wave actually gets to Earth, it has distorted space, but this distortion is so ridiculously small that most scientific instruments aren t advanced enough to pick up the wave (Chang). Rainer Weiss s original idea to create something like LIGO and then, of course, the eventual development of LIGO itself is the only reason that gravitational waves are now able to be detected. The instrument itself that first detected gravitational waves, LIGO, started out as simply an idea of Weiss s back in 1972. He was a professor at MIT at the time, and upon giving his students a problem that related to gravitational waves, the idea of LIGO first began to bloom. He decided that advances in lasers could turn his thought experiment into a real one (Chang). Weiss gathered up two other physicists from Caltech to play with the possibility of building two interferometers, which are now known as LIGO. These interferometers took almost ten years to construct, even after NSF approved LIGO (Chang). The arms of the interferometers are four kilometers long, with one detector stationed in Washington and the other in Louisiana. In space, two black holes collided, and in September of 2015, LIGO picked up the radiated waves from that collision. The gravitational waves hit the detector in Louisiana first, and seven milliseconds later, they reached the Washington
Cook 3 detector (Chang). Despite the fact that this event lasted not even a second, it was a monumental advancement in the physics field. LIGO consists of the largest interferometers in the world. As previously mentioned, the arms of the detectors are four kilometers long, but a passing gravitational wave changes the relative lengths of the arms in each instrument and thus the interference condition of the light beams when they recombine (Chang). These changes in length are quite small, and before 2015 were impossible to measure. However, due to the inclusion of resonant optical cavities in the arms of the detectors, measuring the changes was not a problem. Relating this discovery to Einstein s theory of general relativity creates a bridge in the education system. Einstein s name is well-known, and general relativity is covered in physics courses, but up until September 2015, the detection of gravitational waves didn t seem possible. They could be discussed and examined at length through a theoretical lens, but now LIGO and the data it has collected pertaining to gravitational waves can be included in future textbooks. Gravitational waves, before just an abstract concept, are now cemented in the physics field, thanks to Rainer Weiss and his team. Upgrades for LIGO are already in motion (Fryer). Because of this discovery, students can effectively see the entire picture. Ultimately, physics is a very intense and complex topic. However, just as one would solve a high school physics problem, breaking down the subject into smaller parts helps, which is what Rainer Weiss did all those years ago. He started with just a simple idea involving lasers, and that grew into something so much larger and incredible. He dedicated years of his life to this discovery, building and creating along the way; it didn t happen overnight. Physics is a tree that is constantly growing and branching off, and that s the beauty of it. There will always be something new that needs to be explored, just as there
Cook 4 will always be something that can be reworked. Einstein may have made the prediction regarding gravitational waves, but modern science made the direct detection.
Cook 5 Works Cited Chang, Sung. LIGO detects gravitational waves. Physics Today. 69. 4 (2016). 14. Web. 15 November 2017. Fryer, Chris L. and New, Kimberly C. B. Gravitational Waves from Gravitational Collapse. Living Reviews in Relativity. 14. 1 (2011). Web. 14 November 2017.