Ripples in spacetime could provide clues to missing universe components

There is very little about our theory of the universe. Almost everything is suitable, but there is a fly in the cosmic salve, and a particle of sand in the endless sandwich. Some scientists believe that gravity may be the culprit – and that subtle ripples in the fabric of space-time could help us find the missing piece.

A new research paper co-authored by a scientist at the University of Chicago explains how this might work. Posted on December 21 in Physical review dThe method relies on finding such curved ripples by traveling through supermassive black holes or large galaxies on their way to Earth.

The problem is that something causes the universe not only to expand, but to expand faster and faster over time – and nobody knows what it is. (The search for the exact rate is an ongoing debate in cosmology.)

Scientists have proposed all sorts of theories about what the missing piece was. “Much of it depends on changing the way gravity works on large scales,” said Jose Maria Ichiaaga, co-author of the paper and a postdoctoral fellow at NASA Einstein at the Kavli Institute for Cosmic Physics in UChicago. “And therefore Gravitational waves They are the perfect messenger to see these potential alterations in gravity, if any. “

Gravitational waves are ripples in the fabric of space-time itself. Since 2015, humanity has been able to capture these ripples using LIGO observatories. When two massively heavy objects collide elsewhere in the universe, they create a ripple that travels through space, bearing the imprint of everything it’s made – maybe two. black holes Or the collision of two neutron stars.

In the paper, Ezquiaaga and co-author Miguel Zumalacarigi argue that if these waves strike A supermassive black hole Or a group of galaxies on their way to Earth, the signature of the ripples would change. If there is a difference in gravity compared to Einstein’s theory, then evidence is included in this signature.

For example, one theory about the missing piece of the universe is the existence of an extra particle. Such a particle, among other effects, generates a kind of background, or “middle”, around large objects. If a traveling gravitational wave collides with a supermassive black hole, it will generate waves that mix with the gravitational wave itself. Depending on what you’ve encountered, the gravitational wave signature could “echo,” or appear blurry.

“This is a new way of examining scenarios that could not be tested before,” said Izquiyaga.

Their paper sets out the conditions for how to find such effects in future data. LIGO’s next run is scheduled for 2022, with an upgrade to make the detectors even more sensitive than they really are.

“On our last observation tour with LEGO, we were seeing a new gravitational wave reading every six days, which is amazing. But in the entire universe, we think it actually happens once every five minutes,” said Izquyaga. “In the next upgrade, we can see a lot of these – hundreds of events per year.”

He said that the increased numbers increase the likelihood that one or more waves will travel through a massive object, and scientists will be able to analyze them looking for clues to the missing components.

Zumalácarregui, the other author on the paper, is a scientist at the Max Planck Institute for Gravitational Physics in Germany as well as at the Berkeley Center for Cosmic Physics at Lawrence Berkeley National Laboratory and the University of California, Berkeley.