What gravitational waves can tell us about the birth and death of our universe

Profile: Levon Pogosian

Occupation: Associate professor of physics, SFU

Somewhere in the universe, two massive black holes collided, sending ripples across the fabric of space-time. For the first time ever, these ripples were detected here on Earth, thanks to the LIGO project. The new discovery confirms what Einstein could only theorize: that space and time are like fabric, warped by gravity. This breakthrough means scientists - like Levon Pogosian, an associate physics professor at SFU – have a greater chance of answering some of the more mystifying questions about how our universe began and how it will end. Pogosian is speaking at SFU’s Café Scientifique event on Feb. 26 in New Westminster. See sidebar below for details.

Q&A:

Can you tell me about this new discovery on gravitational waves and why it’s important?

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There are actually three discoveries at the same time. One is the fact they’ve confirmed there are black holes. Two is there are two black holes spinning around each other, which has never been seen before. Finally, the fact these spinning black holes produce gravity waves that they have detected, so gravitation waves have never been detected before.

What does this mean for physics?

First of all, it confirms something we knew should be correct, which should happen. The gravitation waves were predicted by Einstein 100 years ago, but they are so weak that we couldn’t detect them until now. And there were still doubts – maybe something is wrong with space, maybe we don’t understand it completely.

But the fact that we see them confirms our understanding of gravity is correct. That’s one importance. The second thing is once we start detecting these gravity waves, you can use them to learn more things about the universe.

Levon Pogosian
Levon Pogosian, associate physics professor at SFU. - contributed

Can you give us some examples?

Just like sound waves, just like you’re listening to music or the sounds of a musical instrument, you can tell what the instrument is and whether it’s a good one or a bad one. You can infer something by listening to the sound. The same way by listening to these gravity waves, you can learn about black holes, neutron stars, supernova explosions. For example, you can infer whether neutron stars have mountains.

Whether they have mountains?!

Yes, so neutron stars are essentially dead stars; this is after the star burns out. It’s really, really dense, and it’s made just of neutrons, but if it’s not perfectly round. As it spins, it will produce gravity waves, and neutron stars do spin really, really fast. So by studying gravity waves, in principle, we can find out if they have mountains or not just by looking at the gravitational wave signatures.

Tell me a bit about your research and how these new discoveries will impact what you do.

I work a lot on testing gravity, so finding new ways of testing the laws of gravity. The reason I work on it is because I’m trying to understand the reason for the accelerating expansion of the universe.

There’s something people believe is called dark energy, which has repulsive gravity, so it makes the universe accelerate – not just expand and slow down, but expand and expand faster and faster.

Does that mean it will keep expanding till the universe dies?

Yes, (laughter).

Scary stuff.

Today’s discovery essentially allows you to test gravity in a new way. Dark energy is such a mysterious substance that we could also think that maybe it’s not dark energy but maybe gravity behaves in a funny way. When you look at really, really large distances, the universe expands according to laws that are different from Einstein’s laws. With these gravity waves, we could, for example, test the expansion of the universe better, and you can also check if these gravity waves agree with some other theories that try to explain dark energy.

What’s the main question you want to answer for yourself.

There are two questions: one question concerns acceleration, and what makes the universe accelerate. Is it dark energy or that gravity works differently? … Question number 2 is concerned with cosmic strings – can we see them? If we see them, they will tell us about how the universe was when it was a fraction of a second old, which could have something to do with string theory. And string theory is (currently) our best attempt at combining all laws of nature into one theory. Cosmic strings could give us a clue into this theory of everything.

SFU Cafe Scientifique:

Who: Levon Pogosian, associate physics professor from SFU.

What: SFU Café Scientifique, an ongoing series of free, community discussions about science.

When: Feb. 26 from 7 to 9 p.m. Doors open at 6:30 p.m.

Where: Boston Pizza in New Westminster (1045 Columbia St.)

Details: Admission is free, and door open at 6:30 p.m.

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