A Chirp Heard Around the World

Nicholas Moll Marine Science


It all started with a chirp. This may not seem like much but, to many scientists around the world, it is a big deal. “Einstein would be very happy, I think,” said Gabriela González of Louisiana State University. González works for the LIGO, Laser Interferometer Gravitational-Wave Observatory, Scientific Collaboration and to say she is excited would be an understatement. This has been a collaboration of many different scientists worldwide who have been working to detect one of the last predicted phenomenon from the General Theory of Relativity, gravitational waves.

A gravitational waves results from the interactions between two incredibly massive objects that orbit each other in space. They are a ripple in the fabric of spacetime that emanates from the orbiting pair of celestial bodies, at the speed of light. What was detected rises up to a crescendo before abruptly stopping and the stop denotes the collision between these bodies. The data that was collected falls directly under what was predicted originally in Einstein’s original calculations.

These waves are minuscule ripples in spacetime that are on the atomic scale. What does that actually mean? Space-time is most often described as a fabric which is curved by heavy objects, think trampoline, but can only be imagined two dimensionally. These waves actually move outward in a tube like shape. Imagine one of those tunnels that dogs will run through at a dog show. When you apply a force to the top, then the top squishes down and the sides bulge out. When you apply a force to the sides, the sides squish together and the top bulges out. A gravitational wave is kind of like a cycle between these two states in the three dimensional “fabric” of space-time.

These ripples come from a place that is 1.3 billion light years from earth and that wavelength of these ripples are a fraction of the radius of one atomic nucleus when they get to earth. So how do we even detect these small variations in space?

The equipment used is called an interferometer. This involves many buildings that are all over the world, a minimum of a few hundred of miles apart from one another, and that have a very specific design. These buildings have a focal point with two arms that are perpendicular to one another. Each of these arms are a few miles long and have an interior that is shielded from external sources. The purpose is to shoot a laser down the arm and reflect it back to measure any interference. There machines are accurate enough to measure fluctuations smaller than a single proton!

These scientists were able to analyze the “chirp” and found that it was way too low for what they were expecting from orbiting neutron stars. From their calculations, these astrophysicists and mathematicians deemed that the signal had to have come from a pair of binary black-holes, which were orbiting each other. This was theoretically feasible but this was the first time any direct evidence of these systems has been collected. They also found out that the signal had to be about one billion years old to get as small as it was. The craziest part of this notion is that the interferometers were turned on only days before hand as one of the final test to see if it worked. That wave traveled over one billion light years to arrive only a few days after we turned on the exact piece of machinery to detect them. Einstein would be proud and probably a little relieved!


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