{"id":29422,"date":"2016-02-13T11:12:01","date_gmt":"2016-02-13T17:12:01","guid":{"rendered":"http:\/\/news.medill.northwestern.edu\/chicago\/?p=29422"},"modified":"2016-02-13T11:12:01","modified_gmt":"2016-02-13T17:12:01","slug":"listening-to-the-universe-black-holes-give-us-ears-to-gravitational-waves","status":"publish","type":"post","link":"https:\/\/news.medill.northwestern.edu\/chicago\/listening-to-the-universe-black-holes-give-us-ears-to-gravitational-waves\/","title":{"rendered":"Listening to the universe – black holes give us ears to gravitational waves"},"content":{"rendered":"

By Danielle Prieur<\/strong><\/p>\n

Scientists detected the gravitational light waves from two colliding black holes more than a billion light-years away.<\/p>\n

That means it took more than a billion years for that light to reach detectors on Earth. Yet the timing was perfect for\u00a0physicist Gabriela Gonzalez,\u00a0a professor at the Louisiana State University\u2019s Department of Physics and Astronomy. She talked about the discovery Friday in Washington D.C. where thousands of scientists gathered for the conference of the American Association for the Advancement of Science.<\/p>\n

<\/p>\n

She is one of more than 1,000 authors in the LIGO Scientific Collaboration who announced they had detected gravitational waves in a paper published in the journal Physical Review Letters<\/em> on Thursday. The LIGO researchers included\u00a0astrophysicists at Northwestern University.<\/p>\n

\"Dr.
Physicist. Gabriela Gonzalez announces that LIGO has detected gravitational waves on Friday at the AAAS meeting in Washington. Photo courtesy of Danielle Prieur<\/figcaption><\/figure>\n

\u201cIt\u2019s not a search, it\u2019s the actual observation of gravitational waves,\u201d as predicted by Albert Einstein a century ago.<\/p>\n

Gonzalez said they were able to map<\/span><\/u><\/a> their approximate location in the galaxy, and to listen to what a gravitational wave sounded like<\/span><\/u><\/a>, essentially listening to a time capsule from billions of years ago.<\/p>\n

She described listening to the gravitational waves as having “ears in the universe” at AAAS. “We’ll begin listening to the universe,” she earlier told BBC.<\/p>\n

The collision of black holes generated a warping of space time. \u201cFitting it to wave forms\u201d shows that the fit is consistent with Einstein\u2019s theory of general relativity, announced in 1915.<\/p>\n

Gonzalez said that Einstein\u2019s theory was revolutionary. It suggested that \u201cif you have two stars orbiting around each other\u201d the distortion of space time that\u2019s being produced travels away from the system and dissipates energy with it. \u201cEinstein\u2019s theory will tell you that the two stars will get closer and closer together because gravitational waves\u00a0carry away the energy.\u201d<\/p>\n

The detection of these waves confirm what Einstein predicted over 100 years ago: when two black holes come in contact, gravitational waves are produced.<\/p>\n

Although black holes have been observed before, \u201cthese are the first gravitational waves observed from Earth,\u201d Gonzalez said.<\/p>\n

The global LIGO Collaboration involves laboratories around the world that have been searching for decades for gravitational waves.<\/p>\n

\u201cGravitational waves provide a completely new way at looking at the universe. The ability to detect them has the potential to revolutionize astronomy,\u201d said astrophysicist Stephen Hawking in an exclusive interview with BBC News. \u201cThis discovery is the first detection of a black hole binary system and the first observation of black holes merging.\u201d<\/p>\n

So how did LIGO do it?<\/p>\n

\u201cThe first thing is you try to calculate how big the [waves] are and they you need to find a device that can measure those distortions,\u201d said Gonzalez.<\/p>\n

After creating templates for what a gravitational wave produced by two black holes merging, scientists built NSF-funded devices called advanced interferometers to detect the waves.<\/p>\n

LIGO stands for the Laser Interferometer Gravitational-Wave Observatory.<\/p>\n

\u201cIt has a laser beam that is split in two, and it travels in perpendicular arms which bounce back from a mirror,\u201d Gonzalez said. \u201cWhen they come out of the interferometer, the two magnetic waves interfere with each other. If you measure the amount of light produced, you can tell the difference in distance.\u201d<\/p>\n

In order to build a more advanced interferometer, Gonzalez said\u00a0they used special mirrors that, \u201cessentially make the light go back and forth about a hundred times, essentially making it about 100 times more sensitive than it would be.\u201d<\/p>\n

These interferometers had to be sensitive enough to measure the \u201cone thousandth of a proton\u201d distortion caused by gravitational wave GW150914 as it reached Earth, named for \u201ca day [September 14] which thousands of us will always remember,\u201d Gonzalez said, \u201cWhen you see something that grows and oscillates and its oscillations grow in amplitude and frequency, you see the cycles are getting shorter and then they reach a peak amplitude and then they go down.\u201d<\/p>\n

Although it\u2019s not the first time that the interferometers have measured similar patterns of oscillations, Gonzalez said it was clear this pattern was not caused by \u201cnoise\u201d or \u201cartifacts\u201d from the detectors as they had been on previous occasions.<\/p>\n

\u201cI don\u2019t remember any of those artifacts looking like this,\u201d Gonzalez said. \u201cHowever, what convinced us is that 7 milliseconds later we saw the exact same thing in very similar wave form in the Hartford detector.\u201d<\/p>\n

The fact that two interferometers, 3,000 kilometers apart, had the same reading, and that an extrapolation of the measurement over five additional seconds did not fit the pattern, suggested it was a gravitational wave.<\/p>\n

Graphs of LIGO date from Hanford and Livingston<\/h2>\n
\"Graphs
Graphs from Gonzalez’s seminar on Friday, depicting results at Hanford and Livingston.<\/figcaption><\/figure>\n

After confirming that they had detected a gravitational wave, Gonzalez said LIGO went about calculating the energy that had been created by their \u201cmerger\u201d and most interestingly, how long ago the merger happened.<\/p>\n

\u201cThis happened 1.3 billion year ago! Not only long before our lifetime but only when multicellular life was spreading everywhere. So long ago! And it arrived September 14 last year and then it\u2019s gone!\u201d<\/div>\n
<\/div>\n

Although measurements were taken from August through January of this year, September is when the gravitational waves were observed.<\/p>\n

She said this will be the first of many discoveries as technology advances at LIGO and around the world for detecting gravitational waves.<\/p>\n

\u201cThis is the beginning now we now we have two detectors that can analyze binary black holes. In the meantime, detectors are being tweaked, performance is being improved later this summer we expect the Vigo detector in Italy to join the network,\u201d Gonzalez said. \u201cSo now we were not only two ears we will have three we will be able to triangulate.\u201d<\/p>\n

Gonzalez said the possibilities are endless as, \u201cYou have many different wavelengths and the difference in those is the frequency and the wavelength. The same happens with gravitational waves,\u201d said Gonzalez.<\/p>\n

\u201cThere are gravitational waves that are produced by bigger black holes, galaxies colliding and those gravitational waves take minutes to hours and those would be detected by a space detector which we hope flies sometime in the next decade.\u201d<\/p>\n

Don\u2019t expect such monumental discoveries every month, she said. But we should be able to expect one every year as we continue to prove Einstein\u2019s theories and explore our universe.<\/p>\n

Photo at top:\u00a0Albert Einstein on NBC.\u00a0 Einstein’s theory of relativity predicted gravitational waves. Photo courtesy of Bev Sykes<\/a>.<\/div>\n","protected":false},"excerpt":{"rendered":"

By Danielle Prieur Scientists detected the gravitational light waves from two colliding black holes more than a billion light-years away. That means it took more than a billion years for that light to reach detectors on Earth. Yet the timing was perfect for\u00a0physicist Gabriela Gonzalez,\u00a0a professor at the Louisiana State University\u2019s Department of Physics and […]<\/p>\n","protected":false},"author":217,"featured_media":29441,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[452,28,30,585],"tags":[1322,1324,1325,192,1323],"class_list":["post-29422","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-beyond-chicago","category-general-interest","category-public-affairs","category-winter-2016","tag-aaas-conference","tag-gravitational-waves","tag-ligo","tag-promo","tag-washington"],"yoast_head":"\nListening to the universe - black holes give us ears to gravitational waves - Medill Reports Chicago<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/news.medill.northwestern.edu\/chicago\/listening-to-the-universe-black-holes-give-us-ears-to-gravitational-waves\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Listening to the universe - black holes give us ears to gravitational waves - Medill Reports Chicago\" \/>\n<meta property=\"og:description\" content=\"By Danielle Prieur Scientists detected the gravitational light waves from two colliding black holes more than a billion light-years away. 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