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Understanding the cosmos

CMU physicists can benefit from monumental discovery

Contact: Curt Smith

​By Georgios Perdikakis
CMU assistant professor of physics

Last Thursday, humanity made one significant step forward in the understanding of the cosmos.

Scientists from the California Institute of Technology, Massachussets Institute of Technology and Louisiana State University announced that in September 2015 they detected, for the first time, the ripples in space-time created by the dramatic collision of two black holes 30 times the mass of our sun. Gravitational waves, as these ripples are scientifically known, were first suggested by Albert Einstein in his general theory of relativity about a century ago, in 1915.

The technology to detect these waves has been in development for 50 years. The Laser Interferometer Gravitational Wave Observatory, the instrument that detected the gravitational waves, uses reflected laser beams to measure how gravitational waves bend space-time and change the distance between hanging mirrors. But the movement is so small. For the distance of four kilometers between the mirrors of LIGO, the distance measured by the scientists was approximately 10-18 meters. That is 1,000 times smaller than the size of an atomic nucleus, two-and-a-half-miles away!

This new discovery signifies the birth of a new field of astrophysics called gravitational wave astronomy. So far, all observations we have been able to perform of the cosmos were based on some form of electromagnetic light, whether it was optical light, as in regular telescopes, or radio waves, X-rays and Gamma rays. Now gravitational waves can be added to the quiver of tools used to observe the cosmos. Historically, every time such a new technological capability was possible, new surprising discoveries were made.

CMU's research is related to the discovery by LIGO in an exciting way. The quest to discover the origin of elements — one of the main goals of nuclear physics research performed by CMU faculty at the nearby Facility for Rare Isotope Beams and other labs — is related to events that could be detected in the future by LIGO. 

Scientists expect elements are created when massive objects, like neutron stars and black holes, collide or when stars explode as supernovae. When these events happen gravitational waves will be emitted. When they are detected and located by gravitational observatories in the future, and observed by astronomers, they will provide important details of the element-creating collisions or explosions. Nuclear astrophysicists will use this information in their models to understand how nuclear reactions create elements in those catastrophic cosmic events.​

About Georgios Perdikakis

Perdikakis studies how nuclear reactions play a role in the evolution and death of stars, and give rise to spectacular phenomena to produce the chemical elements our world is made from. He seeks to understand how elements are created in stellar processes by nuclear reactions that fuel them, by designing nuclear astrophysics experiments in accelerators in the U.S. and abroad.

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