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Georgetown University’s Newspaper of Record since 1920

The Hoya

Georgetown University’s Newspaper of Record since 1920

The Hoya

Laser Interferometer Gravitational-Wave Observatory Detects Ripples in Spacetime


For most of us, the mention of “technological innovation” brings to mind images of the technologies that have become useful for our everyday lives. We imagine aspiring app developers lounging about the coffee shops of San Francisco, Bill Gates camping out in his office overnight or, as a throwback, Thomas Edison and his crew developing the electric lightbulb. Although innovative in their own time and originally rather expensive as prototypes, the innovations we remember most fondly are those that were eventually released to the masses. These technologies are featured in storefronts around the world at competitive prices and are probably updated every one or two years with some vague, marginally useful improvement to secure sales, even when the company has run out of any actual ideas. I am thinking about a fruit that starts with the letter “A.”

Some of the greatest innovations known to mankind, though, are the niche tools that are only utilized by people working in very specific professions. Long before personal computers were available to the average person to use for average tasks, the early precursors of computers enabled scientists to make complex calculations at an appreciably faster rate. However, this fascinating innovation was not very useful for highly technical fields like spaceflight until the 1970s. All of the calculations to build the Apollo 11 spacecraft, which launched Neil Armstrong, Michael Collins and Buzz Aldrin to the moon in 1969, were done by hand. The machine calculations for the Apollo 11 mission were verified by hand because people did not yet trust the accuracy of the number- crunching done by the newfangled computers.

Recently, researchers at the Laser Interferometer Gravitational-Wave Observatory announced the detection of honest-to-God gravitational waves, confirming Einstein’s general theory of relativity.

A wave is a repeated pattern of movement travelling through some medium. A stadium wave is the travelling pattern of rising and falling hands. A tidal wave is the travelling pattern of water rising and falling through the ocean. A gravity wave is the travelling pattern of the fabric of “spacetime” vibrating through existence. These vibrations in the four-dimensional spacetime fabric are caused when an object with mass distorts the fabric by mere virtue of its mass. This is a bit like vibrations in a two-dimensional trampoline fabric when your feet distort that fabric by mere virtue of your body’s mass. Spacetime is the paper on which the universe is drawn, and the universe can be wrinkled just as a picture drawn on a piece of paper can be.

When it comes to observing things in deep space, we have been limited to what we can see. Since space is big and light does not go everywhere we would like it to, there is a lot we cannot see. With the ability to detect gravity waves, we now have the ability to find signs of theoretically everything in the universe that has mass, like black holes.

The innovation required to get to this point, though, was extensive. As you can imagine, detecting ripples in the fabric of spacetime is not something you can do with a compass and a yardstick. An interferometer, which was used by LIGO to detect gravitational waves, is a device that combines two light waves on top of each other to gather information about the waves, such as the phase of the waves, at a data collection point. The phase of a wave at a point is, loosely, the pattern that the wave is taking at that point. In the interferometer, one beam of light was split down two 2.5 mile-long tubes that were perpendicular to each other, each with a mirror at the end. Both beams would return to the detection point at the center out of phase — that is, one beam would have a trough, the low part of the wave, at the detection point while the other had a peak, the high part. The trough and the peak would cancel each other out to create no light.

When spacetime ripples through the long tubes, it changes the distance the light has to travel. One tube changes more than the other, giving that beam of light a longer path to follow. As a result, the two beams do not arrive back at the detection point completely in phase. The beams do not cancel each other out and light is therefore detected. Scientists at LIGO, who found a delay in the time the light took to get from one detector to the other, announced the delay was caused by a ripple in spacetime. While experimenters have used interferometers before, never before has such a large or precise one been required. The project racked up a cost of $620 million.

Since the revolutionary shakings of Einstein and Bohr in the early 20th century died down, physics has seemed a little slow in comparison. But, at midnight before the morning LIGO announced their discovery, Dr. Joseph Serene, the professor of my “Introduction to Quantum Physics” course last semester, alerted the class about the news by email.

“I know what they will announce, and it gives me goose bumps,” he said.

The news gives students of all the natural sciences a boost in morale; we may very well be training for an age of explosive discovery. Instead of making do with consulting gigs and computer chip optimization research, we may uncover secrets of the universe never before imagined. Regardless of what you study, I can assure you that there is something left in your field to discover. So, mass-containing being, let’s start making waves. Wait, you already are.

Patrick Soltis is a sophomore in the College. INNOVATION SMACK TALK appears every Friday.


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