Metaphysic Study

Charmed Series Book of Shadows: Time Ripples

In 1915 Albert Einstein made big waves in physics by propounding a radically new way to think about space, time and gravity. His idea, the general theory of relativity, sent ripples churning through 20th century understanding of the universe that led physicists to the big bang, black holes and brave new worlds of unified theory that reach to embrace all of physics.

Among the still rippling effects of general relativity is Einstein's prediction that moving objects give off gravitational waves. Much like vibrating electrons give off electromagnetic radiation, which allows us to listen to radio and watch TV, the accelerating movements of massive objects in space, such as supernova explosions and black holes, produce gravitational radiation, according to Einstein — ripples moving at the speed of light through the four-dimensional fabric of spacetime.

Important evidence that Einstein was right about gravity waves came from precise measurements of two neutron stars orbiting each other — work which won the 1993 Nobel Prize in physics; the gradual inspiral of the orbits agrees with general relativity theory's predictions for the energy loss that would occur from gravitational radiation. Still, compared to other kinds of radiation, gravity waves are weak, notoriously difficult to detect, and proof of their existence remains a matter of circumstantial evidence.

To clinch the case, scientists at Caltech and MIT, with funding from the National Science Foundation, are building LIGO, the Laser Interferometer Gravitational-Wave Observatory. LIGO's ability to detect gravity waves sometime early in the next century depends critically on a team of University of Pittsburgh physicists. As part of the NSF's Binary Black Hole Grand Challenge Alliance, astrophysicist Jeffrey Winicour and his coworkers are developing computational tools to simulate how black holes emit gravity waves, and in particular gravity waves from two black holes orbiting each other — a binary black hole.

"Calculating the waveforms from the inspiral and merger of binary black holes is important to the success of LIGO," says Winicour, "and it's the prime goal of the Grand Challenge." In late 1997, their computations on the CRAY C90 at Pittsburgh Supercomputing Center marked a milestone along the path toward their goal. Using an innovative new approach, they carried out the first stable, 3D simulations of a single black hole moving through space over a long period of time — an objective that physicists ten years ago saw as "the Holy Grail of numerical relativity."

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