Ripples in Spacetime
Ripples in Spacetime
For an Australian, the ideal Christmas celebration consists of a family barbecue outside on a balmy summer night. As a Pennsylvania native, however, I was determined to get a white Christmas, even in the dead of summer Down Under, so I headed to Mount Kosciuszko, Australia’s tallest peak, in search of snow.
At just over 2200m, Kozzy — as the locals call it — is by far the smallest of the Seven Summits, but the Snowy Mountains lived up to their name, and I had a snow ball fight on Boxing Day after all.
I arrived in Melbourne in August — the end of the Australian winter — to begin my 10-month tenure as a Fulbright Postgraduate fellow with the Laser Interferometer Gravitational Wave Observatory (LIGO) Scientific Collaboration at Monash University.
My research focuses on gravitational waves – oscillating signals from distant galaxies produced by the violent acceleration of extremely massive objects. Imagine dropping a bowling ball on an outstretched bed sheet; the sheet would form a well around the ball. This is the same way spacetime reacts to the presence of massive objects like stars, planets, and black holes. Now imagine you set two bowling balls spinning around each other on the sheet; they’d produce circular ripples like a rock thrown into a still pond.
When two black holes merge, energy is released as oscillating waves that can be detected across vast distances
When two highly dense objects like black holes or neutron stars spiral into each other in a death dance until their eventual merger, they produce ripples in the fabric of spacetime that radiate out across vast distances in the form of gravitational waves. By the time these perturbations reach Earth, their amplitude is smaller than one one-thousandth of the diameter of a proton, so extremely sensitive instruments are needed to detect them.
The LIGO detectors, with their 4km-long vacuum-sealed laser cavities, measure gravitational waves by looking for characteristic interference patterns in the recombined laser light.
I got my start with LIGO the last time I’d been at Monash for a summer project two years ago, and I knew I had to find a way to come back. During my previous visit, the gravitational wave group consisted of just me and my supervisor, but now the group at Monash has about 15 researchers including postdoctoral fellows, graduate students and professors.
This growth is due in large part to LIGO’s momentous announcement of the first direct detection of gravitational waves from the merger of two black holes in 2016, confirming Einstein’s 100-year old prediction of their existence. This merger released the energy of 3 suns as gravitational waves, and yet here on Earth, we wouldn’t have been able to detect this first-of-its-kind astrophysical event without LIGO.
Artist’s depiction of two merging black holes, Images courtesy CaltechMITLIGO Laboratory
A few weeks before I arrived in Australia, LIGO detected gravitational waves from a new source — a pair of neutron stars, which produced a huge electromagnetic explosion known as a gamma-ray burst when they collided. This proved that the ejected material from this type of coalescence is the primary source of heavy element (gold!) formation in the universe. My research uses coincident gravitational wave and electromagnetic detections of this nature to constrain the properties of gamma-ray burst jets.
Another reason for the precipitous growth of the Monash GW group was the launch of the Australian Research Council Centre of Excellence for Gravitational Wave discovery, or OzGrav, which established a national community in Australia for coordinating gravitational wave research across six universities.
Through OzGrav, I’ve presented at conferences in Melbourne and in Perth, forging international collaborations and receiving feedback from the world’s top gravitational wave and gamma-ray burst scientists.
Even across different sub-fields in the Monash Center for Astrophysics, there is a heightened level of community and collaboration. The whole department gathers for astro-coffee every day at 11a.m., and postgraduates get together once a week to discuss new papers.
Mountains and scientific collaborations aren’t the only things that get abbreviated in Australian culture. Breakfast becomes brekkie; afternoon, arvo; service station, servo; McDonald’s, Maccas, etc.
While Australia and the U.S. are very culturally similar, the linguistic and culinary differences are the most apparent. Peppers are called capsicums, flip-flops are called thongs, and “parma” (chicken parmesan) is served with “chips” (fries) and never spaghetti.
When I return to the U.S., I’ll be bringing back several boxes of chocolate-dipped cookies called Tim Tams, but also a deeper understanding of statistical data analysis methods, multimessenger astronomy, and America’s role in the international scientific community.
Originally published on Penn State News