Guest Blog: Surf's up! Riding gravitational waves

Posted by Nicole Kiefert
on Friday, August 11, 2017

GIF Created by Bronwen and Paul Lasky.
by Abigail Stephens and Keegan Engelking

The individual trapped in the screen to the left is Dr. Paul Lasky. Although I stated trapped, he voluntarily gave up his time at in Melbourne to videoconference with our 2017 SHSU BLAsT class at the CSIRO Astronomy and Space Sciences campus in Marsfield, NSW. This Monash University researcher is a member of the Australian Centre for Gravitational Wave Research (OzGrav), the LIGO Scientific Collaboration, and the Parkes Pulsar Timing Array. Today we traveled back in time to 1915 when Einstein presented his theory of gravity to the Prussian Academy, neatly explaining the orbit of Mercury and revolutionizing the way we think about gravity. Einstein presented what looked like a pretty simple field equation which solved some of the problems in the way gravity behaved and that couldn’t be fit by Newton’s theory. Einstein’s weird idea was supported in 1919 by Sir Arthur Eddington and colleagues, who observed bending starlight during the solar eclipse. In fact, this is something that our group is HOPING to witness in Casper, Wyoming, during the upcoming total eclipse. Despite looking simple, Einstein’s equation is so hard to comprehend that most physics departments do not even present it to university students until they are upperclassmen.

Lasky lectures on Lego LIGO laser light. Apparently to make a workable LIGO detector that would compress/stretch by a single Lego block, you would need to make its arms long enough to reach from here to the Galactic center. // Photo by Scott T. Miller
Now we traveled forward in time, and Dr. Lasky told us that without this equation we would not have advancements such as GPS, understanding neutron stars, and the discovery of black holes.

Black holes were really where Lasky’s story took off. Like ducks swimming across a pond, black holes – and all masses, for that matter -  create ripples in spacetime.  These ripples can even be detected when something extreme happens, like two merging black holes. In fact this is what our gravitational wave ‘telescopes’ first detected in September 2015. The black holes in question were orbiting each other at about half the speed of light, (really freaking fast!). They merged within a fraction of a second, sending out these ripples we call gravitational waves. These black holes were about 30 times the size of our sun, and their merger released more energy than the rest of the universe combined during that fraction of a second. Seems easy to detect, right?

Wrong.

The infamous 'chirp' detected at both LIGO facilities. // from 'The Dawn of Gravitational Wave Astronomy' presentation, Paul Lasky
Meet LIGO! These two facilities detected the merging of the two black holes by using a highly sensitive laser. LIGO shoots a laser into a mirror down two “arms,” which then reflect the light back and scientists can measure how well the light waves match up after the return trip. When a gravitational wave rolls through, this stretches and compresses spacetime, so one arm’s laser will come back a bit earlier or later compared to the other. How much earlier or later? Well, the wave we “felt” changed the size of LIGO’s 4-km-long detection arms by one-thousandth the width of a proton… at which point the whole class went, “Whaa!?” This is due in part to the billion or so light years of distance between us and the merging black holes, and also to the fact that gravitational waves are so week. And since we can’t feel or measure this on our own, we need a large, highly sensitive machine like LIGO. With this technology, we can ride the wave to a future with better understanding of our universe.  Cowabunga Dude!

ABOUT (one of) THE AUTHORS:

My name is Abigail Stephens and I am a senior at Sam Houston State University with a major in Communication Studies and a minor in Family and Consumer Science. I chose to come on this study-abroad because I've always wanted to know more about astronomy, and this would be the most hands on I would ever get. Between comparing the skies in both hemispheres  and ending with a total solar eclipse, this is a bucket list trip!

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