An international group of scientists have harnessed the Milky Way as an antenna to find the first evidence of low-frequency gravitational waves — ripples in the fabric of the universe that warp space-time.
The discovery, revealed in the journal The Astrophysical Journal Letters Wednesday, establishes the first evidence of the existence warping phenomenon initially predicted by Einstein's Theory of Relativity but never observed until now.
The study drew on 15 years of data captured by high-powered radio telescopes in Puerto Rico, West Virginia and New Mexico.
Kathryn Crowter, a PhD candidate at the University of British Columbia's Department of Physics and Astronomy and one of 190 co-authors on the study, said the discovery has opened the door to "break physics" as we know it.
"Most of the information we have comes from like looking at the universe, through light, whereas this is completely different," she said. "This is opening a new window on our universe."
Gravitational waves are thought to come from the movements of massive objects, like black holes orbiting each other. But unlike the gravity well of a sun, moon or planet, gravitational waves echo across the universe, stretching and compressing the physical existence.
Imagine a lake with two boats on it. As they move, ripples fan out in all directions, changing the surface of the water. But that analogy only goes so far because scientists can't actually see the ripples. Instead, they're forced to measure how the universe is being warped by a nearly invisible force.
An array of cosmic clocks
To measure how gravitational waves are warping our galaxy, the international team selected 68 highly predictable pulsars — what's left after a star uses up its fuel and goes supernova. The "undead stars" are so dense they contain the mass of a star one and a half times the size of our sun, squished into the size of a city.
"I have all these fun facts: If you squished all humans in the world to the size of a sugar cube, that's how dense it is," said Crowter.
Pulsars have a powerful magnetic field that spins up to hundreds of times a second. Because a pulsar radiation gets ejected along its magnetic axis. At one point in the spin, the "pulse" points at Earth at such regular intervals that rival an atomic clock's precision.
Using the speed of light as a constant, the team measured the time these pulses took to reach Earth. Early arrivals suggest gravitational waves have compressed space in that part of the galaxy, whereas late arrivals suggest existence has been stretched.
Interstellar gases and interaction between gravitational waves complicates the picture — like the ripples of raindrops falling on a lake — but modelling later helped the scientists see a clearer picture.
"We had to build a detector that was roughly the size of the galaxy," said Michael Lam, a co-author and research scientist at the SETI Institute.
The distances are both immense and microscopic.
The pulsars Crowter and her colleagues used as part of their cosmic antenna ranged from nearly 450 light years to more than 20,000 light years away.
In analyzing the years of data, the scientists found that gravitational waves are likely changing those distances to Earth, making them either a few hundred metres shorter or longer. At the planetary scale, the waves appear to be warping the size of Earth by about the size of a virus.
Canadian telescope to help refine search for gravitational waves
Crowter said the next step is to combine the data with other experiments around the globe and eventually tie in the CHIME radio telescope in British Columbia's Okanagan Valley.
That could lead to building better maps of gravitational waves, said co-author Luke Zoltan Kelley, a researcher at the University of California Berkeley.
It could even lead to the discovery of the waves' origins — giant black holes orbiting each other, or the moment just after the Big Bang, Crowter said.
"That's also going to be incredible," she said. "We can observe fainter and fainter." stuff."
"You can't find that with light."
