Gravitational waves detected for first time

Published: February 25, 2016

THE DETECTORS depicted above are sensitive enough to detect the subtle gravitational waves. The sensor works by refracting a light beam down two tubes each 2.5 miles long. The light is reflected back to the beam splitter where they should cancel each other. If a gravitational wave were to strike the machine, it would bend the beam of light causing them not to intersect and cancel each other out. The difference in timing between the beams of light allows physicists to detect the waves. The information gathered from the two observatories can then be used to locate the source of the wave.

PHOTO COURTESY OF WIKIMEDIA COMMONS / THE DETECTORS depicted above are sensitive enough to detect the subtle gravitational waves. The sensor works by refracting a light beam down two tubes each 2.5 miles long. The light is reflected back to the beam splitter where they should cancel each other. If a gravitational wave were to strike the machine, it would bend the beam of light causing them not to intersect and cancel each other out. The difference in timing between the beams of light allows physicists to detect the waves. The information gathered from the two observatories can then be used to locate the source of the wave.

ALEX HABER
Science & Tech Editor

Over 100 years ago, Albert Einstein, Ph.D., put forth his theory of general relativity, but only now are some of the implications and predictions of the theory receiving evidence for their existence. Scientists of the Laser Interferometer Gravitational-Wave Observatory, LIGO, with locations in Louisiana and Washington, detected gravitational waves for the first time. The waves were detected Sept. 14, 2015.

Gravitational waves, as predicted by Einstein, are ripples in space and time. The acceleration of massive objects in space, he proposed, causes the waves. The waves detected emerged from the collision of two black holes over a billion years ago. The collision of the two black holes released an immense amount of energy in a fraction of a second. Although the collision occurred a billion years ago, gravitational waves are still being emitted from the collision site.

The gravitational waves released by the collision travel across the universe at the speed of light. As these waves move, they compress and stretch the space around them in opposite directions. Over distance, the strength of the waves weakens, and becomes so weak that they are almost undetectable here on Earth.

In order to detect the subtle waves, two of the most sensitive instruments ever built were constructed. The two observatories are spaced 1,865 miles apart as to be able to triangulate the source of the wave once it has been detected. The observatories are identical in structure. The detector works by sending a light wave out which is refracted off of a mirror. The mirror splits the light and sends it down two identical pure glass tunnels, each 2.5 miles long. At the end of the tunnels is a mirror. The mirror then reflects the light back. Since the tunnels are exactly the same distance, when the reflected light returns to where it was split, they will cancel each other out.

If a gravitational wave were to interrupt the beam of light, the light would be off course by a fraction of a second. This disturbance would prevent the lights from canceling each other out and thus the light will strike a wall. Physicists at LIGO then turned this disturbance into a sound. For the first time, scientists were able to hear a disturbance from space.
The detection of gravitational waves opens up a new field of astronomy and physics for the next generation. Finally detecting these elusive waves has helped to paint a bigger, more expansive picture of the universe as we see it. The discovery of gravitational waves proves one of Einstein’s wildest theories and confirms his genius. The findings from the project were recently published in the journal “Physics.” The paper includes over 1,000 authors on the project.

Contact the writer: alexander.haber@scranton.edu

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