Understanding gravitational waves

Physicist and educator Umberto Cannella joins Andrea Vasquez in a Google Hangout to discuss the recent discovery of gravitational waves, or ripples in the fabric of space and time.


Up next, reporter Andrea Vasquez has an interview via Google Hangout.

The scientific world was abuzz when a team of scientists announced that they had recorded the sound of two black holes colliding 1.3 billion light years away.

The discovery is the first direct proof of the existence of gravitational waves, or ripples, in the fabric of space and time.

Gravitational waves were first predicted by Albert Einstein in 1916, as part of his Theory of General Relativity, and they have major implications for the study of black holes and the dark universe.

Here to help us unpack the groundbreaking discovery is physicist and educator Umberto Cannella.

Can you explain what happened and why this took so long to figure out?

February 11th, the big discovery has been announced, but it was the end of a process of continuous check and cross-check that started around mid-September last year.

And that day in September, the story goes that the two instruments, the microphones of the universe, were on just barely ready after major upgrades, and they immediately detected these gravitational waves from the universe.

And this wave was already traveling at the speed of light, covering the distance of 1.3 billion light years from us.

So, what did scientists take away from that?

Well, first of all, the theory of gravity that Einstein built is reinforced.

And the nice thing about science is that not even Einstein deserves belief if it's not proved.

But now that we know they exist, we can access information about the universe that we were deaf about.

What is a gravitational wave, and how exactly is it created?

We're all familiar with throwing pebbles in ponds.


From the point of impact, we can see these ripples going further and further and then dying out.

We now replace water with the space in the universe.

It's pretty similar.

We only need heavy pebbles that in our case are black holes or very complex stars that are called 'neutron stars.'

These stars and these black holes have a heavy mass, and that's what's creating this ripple?


In the usual way of describing things, one can think of a trampoline that is elastic and receives a deformation, a dent, by a bowling ball, for example.

And the bowling ball could be the Earth, could be the Sun.

According to the mass, it would have bigger dents.

So, what effects are these gravitational waves having on the environment around them?

Well, close to this very romantic encounter, things can really be a little bit violent.

The energy's huge in terms of the formation of space.

It's like if a wave was trying to knead us, like pasta.

So, a coming wave, a gravitational wave, heating our bodies would stretch our bodies top from bottom, like spaghetti, squeezing our hips at the same time.

But as if it were not enough, one second after, the effects would reverse.

So, our hips would be pulled outwards, our arms, too, and our head would be squashed towards our feet like a lasagne.

And for something that's so far out in this deep darkness of space, how are scientists able to observe and measure these waves?

Because of the peculiar effect that we discussed, if you build an instrument that is shaped like the letter 'L,' you are sensitive to these alternations of the formation, even if the deformation is minuscule.

Why is that?

Is it bouncing off of one to the other?

The light in the instrument is bouncing from the ends of the two tunnels in the 'L,' and the two arms of the tunnels are squeezed or stretched, and this alternation is what can make them apparent in the data.


So, we're sending out these instruments to collect these measurements?

We will send instruments out in space.

For the moment we have two on Earth.

Could this impact things like space travel and other things that affect what we're actually doing here on Earth?

Everyone wishes so, even a few scientists, because it would be affecting the so-called fabric of space and time.

And because we are inside it, we can think of shortening the path between us and a star.

And how often are these gravitational waves rippling out into the universe?

That's a very deep question because so far we have been deaf, so we have basically no idea.

There were estimates that said we could have as many as a thousand signals per year.

Other estimates said that we would have to be lucky to have one signal per year, because we were deaf, so we didn't have many terms of comparison.

So, it's completely new.

That's why people are really excited about it.

And how long do we have to wait until we start getting the data back to give us a better picture?

Well, scientists are very thorough in their analysis because you have to disprove your own self, basically.

You don't want to believe what you would like to be true.

And that's why they have waited all along the rumors spreading on the Web, on the Internet, 'cause they wanted to be as sure as possible.

But once the procedure has been tested, and its nature is gentle enough, we could get one very soon.


Well, we look forward to seeing it.

Thank you, Umberto, for being with us.

My pleasure.