February 11, 2016
For the first time, scientists have observed ripples in the fabric of spacetime called gravitational waves, arriving at the earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein’s 1915 general theory of relativity and opens an unprecedented new window onto the cosmos.
Gravitational waves carry information about their dramatic origins and about the nature of gravity that cannot otherwise be obtained. Physicists have concluded the detected gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes had been predicted but never observed.
The gravitational waves were detected on September 14, 2015 at 5:51 a.m. EDT by both of the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington. The LIGO Observatories are funded by the National Science Foundation (NSF), and were conceived, built, and are operated by Caltech and MIT. The discovery, accepted for publication in the journal Physical Review Letters, was made by the LIGO Scientific Collaboration, which includes the GEO Collaboration and the Australian Consortium for Interferometric Gravitational Astronomy, and the Virgo Collaboration using data from the two LIGO detectors.
Seven Texas Tech University researchers are members of the LIGO Scientific Collaboration: professor Benjamin Owen, assistant professor Alessandra Corsi, postdoctoral researchers Santiago Caride, Robert Coyne, Ra Inta and Nipuni Palliyaguru, all in the Department of Physics; and undergraduate Department of Mechanical Engineering major Chance Norris.
“For most of human history, everything we learned about the universe outside Earth’s atmosphere came through light waves,” Corsi said. “In the last century we started seeing other parts of the electromagnetic spectrum – radio, X-rays and so on, different wavelengths but the same fundamental force of nature.”
Owen added, “Cosmic rays and neutrinos let us see the ‘dark side’ of the universe via the second and third fundamental forces. Einstein predicted the fourth fundamental force, gravity, also makes waves that could tell us even more about the dark side of the universe. He thought they would be too faint to detect, but 100 years later we’ve done it.”
One of the two data analysis algorithms that detected the gravitational waves relied on Owen’s work in the last 20 years to efficiently search for signals, and Owen spent three years supervising the stress testing of the other algorithm. Corsi has worked for years at the interface of gravitational-wave physics and astronomy and is one of the key players in the effort to enable sky searches for electromagnetic counterparts to invisible gravitational waves.
Coyne, Palliyaguru and Norris have joined her in this endeavor, which includes searching LIGO data for gravitational waves that leave detectable electromagnetic signatures. Caride and Inta have worked extensively to assure the quality of LIGO data. The Texas Tech group also looks ahead: All members work on searches for long and short gravitational wave signals from neutron stars, which should be detected in the coming years and will carry information not only on gravity but also on matter under the most extreme conditions in the universe.
LIGO research is carried out by the LIGO Scientific Collaboration (LSC), a group of more than 1,000 scientists from universities around the United States and in 14 other countries. More than 90 universities and research institutes in the LSC develop detector technology and analyze data; approximately 250 students are strong contributing members of the collaboration. The LSC detector network includes the LIGO interferometers and the GEO600 detector. The GEO team includes scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI), Leibniz Universität Hannover, along with partners at the University of Glasgow, Cardiff University, the University of Birmingham, other universities in the United Kingdom and the University of the Balearic Islands in Spain.
Hanford achieves interferometer lock
On December 12, 2014, LIGO Hanford achieved its first interferometer "lock."
"Locking" refers to the times during which infrared light resonates throughout the interferometer under computer control.
(Credit: Caltech/MIT/LIGO Lab)
LIGO originally was proposed as a means of detecting these gravitational waves in the 1980s by Rainer Weiss, professor of physics, emeritus, from MIT; Kip Thorne, Caltech’s Richard P. Feynman Professor of Theoretical Physics, emeritus; and Ronald Drever, professor of physics, emeritus, also from Caltech.
Virgo research is carried out by the Virgo Collaboration, consisting of more than 250 physicists and engineers belonging to 19 different European research groups: 6 from Centre National de la Recherche Scientifique (CNRS) in France; 8 from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; 2 in The Netherlands with Nikhef; the Wigner RCP in Hungary; the POLGRAW group in Poland and the European Gravitational Observatory (EGO), the laboratory hosting the Virgo detector near Pisa in Italy.
Gravitational-Wave Observatories Across the Globe (Credit: LIGO)
The discovery was made possible by the enhanced capabilities of Advanced LIGO, a major upgrade that increases the sensitivity of the instruments compared to the first generation LIGO detectors, enabling a large increase in the volume of the universe probed – and the discovery of gravitational waves during its first observation run. The National Science Foundation leads in financial support for Advanced LIGO. Funding organizations in Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council, STFC) and Australia (Australian Research Council) also have made significant commitments to the project. Several of the key technologies that made Advanced LIGO so much more sensitive have been developed and tested by the German UK GEO collaboration.
Significant computer resources have been contributed by the AEI Hannover Atlas Cluster, the LIGO Laboratory, Syracuse University, and the University of Wisconsin-Milwaukee. Several universities designed, built, and tested key components for Advanced LIGO: The Australian National University, the University of Adelaide, the University of Florida, Stanford University, Columbia University of the City of New York, and Louisiana State University.
The LIGO Laboratory operates two detector sites, one near Hanford in eastern Washington (left), and another near Livingston, Louisiana (right). (Credit: Caltech/MIT/LIGO Lab)
The colored lines represent different probabilities for where the signal originated:
the purple line defines the region where the signal is predicted to have come from
with a 90 percent confidence level; the inner yellow line defines the target region
at a 10 percent confidence level.
LIGO: The First Observation of Gravitational Waves (3:35)
On September 14, 2015, LIGO observed ripples in the fabric of spacetime. This video narrative tells the story of the science behind that important detection. (Credit: Caltech)
LIGO: Opening a New Window Onto the Universe (5:15)
This video narrative tells the story of the history and legacy of LIGO from the genesis of the idea to the detection in September 2015. (Credit: Caltech Strategic Communications and Caltech AMT)
Two Black Holes Merge Into One (0:30)
A computer simulation shows the collision of two black holes, each roughly 30 times
the mass of the sun, with one slightly larger than the other. The event took place
1.3 billion years ago.
The Sound of Two Black Holes Colliding (0:12)
In the first two runs of the animation, the sound-wave frequencies exactly match the frequencies of the gravitational waves. The second two runs of the animation play the sounds again at higher frequencies that better fit the human hearing range. The animation ends by playing the original frequencies again twice. (Credit: LIGO)
Warped Space and Time Around Colliding Black Holes (1:13)
This computer simulation shows the warping of space and time around two colliding black holes observed by LIGO on September 14, 2015. (Credit: SXS)
Journey of a Gravitational Wave (2:55)
LIGO scientist David Reitze takes us on a 1.3 billion year journey that begins with the violent merger of two black holes in the distant universe. The event produced gravitational waves, tiny ripples in the fabric of space and time, which LIGO detected as they passed Earth on September 14, 2015. (Credit: LIGO/SXS/R. Hurt and T. Pyle)
The Department of Physics is active in a broad range of research and teaching activities designed to prepare undergraduates for challenging careers in science and technology. Graduates of the department have gone on to successful careers at universities, national laboratories, and in industry.
The department offers the Bachelor of Science degree in physics, and in cooperation with the College of Engineering, also offers courses leading to the Bachelor of Science in engineering physics.Society of Physics Students at Texas Tech University