Why a rumour about the discovery of something Einstein predicted over 100 years ago is going viral

LIGOUploaded by Cfoellmi~commonswiki on WikipediaOne of the two tunnels that make up LIGO based in Hanford, Washington.

On Monday, theoretical physicist Laurence Krauss sent the scientific community on Twitter reeling when he suggested that researchers may have detected, for the first time, an astrophysical phenomenon called gravitational waves.

Right now, the rumour is just that. The scientists to which the rumour refers work at the Laser Interferometer Gravitational-Wave Observatory (LIGO) and told Business Insider that there is no basis for such a discovery, yet.

“We are still taking data, and we won’t finish analysing and reviewing results until at least a month or two later,” Gabriela Gonzalez, LIGO spokesperson and Louisiana State University physics and astronomy professor, told Business Insider. She added: “The instruments are working great, but … I don’t have any news with analysis results to share, yet.”

But what if the rumour turns out to be real? Well, the prospect of what that would mean for science is what earned Krauss’s Tweet 4,250% more retweets than his usual 40 or so — overnight.

What are gravitational waves and why do they matter?

Gravity wavesLLacertae on FlickrArtist’s concept of gravitational waves in space.

Albert Einstein first predicted the existence of gravitational waves in 1916.

According to his theory of general relativity, a number of incredibly powerful cosmic collisions across the universe will generate measurable ripples in the fabric of space-time called gravitational waves.

For example, as two galaxies collide, the supermassive black holes at their centres will also merge, but before they do, they will first enter into a deadly cosmic dance where the smaller black hole spirals into the larger one.

As the smaller black hole moves inches toward it’s inevitable doom, it moves increasingly faster. This acceleration generates gravitational waves.

However, scientists have yet to confirm this theory with observational evidence, which is why LIGO is so important.

“The detection of gravitational waves would be a game changer for astronomers in the field,” Clifford Will, a distinguished profess of physics at the University of Florida who studied under famed astrophysicist Kip Thorne told Business Insider in 2015. “We would be able to test aspects of general relativity that have not been tested.”

Not only that, the ability to observe gravitational waves would open a whole new frontier of astronomy. The same way that astronomers today use light waves to study the universe, they could also use gravitational waves to see cosmic objects — such as colliding black holes — like never before.

How to snag a gravitational wave

LIGO first began sniffing the skies for gravitational waves in 2002. And between 2002 and 2010, the $620 million experiment came up empty handed.

To better the odds, engineers began upgrading LIGO to make it 10 times more sensitive to gravitational waves. Last September, scientists turned the new-and-improved machine on and began taking data with, what is now called Advanced LIGO.

The way Advanced LIGO works is that it consists of two identical machines that are located 1,865 miles apart — one is in Livingston, Louisiana and the other is in Hanford, Washington.

At each detector, there are two equally-long tunnels that have a mirror at the end (one of the mirrors is shown in the image above). Scientists split a laser beam in two and then fire each half down one of the two tunnels. When the beams reflects off the mirror, the two beams should return at the same time, since they’re both travelling at the speed of light.

However, if a gravitational wave passes through the detector the same time the laser is travelling through the two tunnels, there will be a slight difference in time when the first half of the beam returns compared to the other half.

Compared to the length light waves we see with our eyes, which are micrometres in size (about the width of a human hair), gravitational waves are huge. This is why the distance between each LIGO detector is over 1800 miles, because that’s about how long astronomers think a gravitational wave should be.

Therefore, if one detector observes a gravitational wave, it should mean the other detector should measure the same signal, offering immediate confirmation that the observation at the first detector isn’t a fluke.

Scientists at LIGO aren’t taking any chances with this experiment. Before they announcing a discovery, the data will have been fully vetted twice-over by their expert peers.

But if they do succeed, it will revolutionise astronomy as we know it.

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