|
 But scientists have been able to find only indirect evidence of
their existence. On Thursday, at a news conference called by the
U.S. National Science Foundation, researchers may announce at long
last direct observations of the elusive waves.
Such a discovery would represent a scientific landmark, opening the
door to an entirely new way to observe the cosmos and unlock secrets
about the early universe and mysterious objects like black holes and
neutron stars.
Scientists from the California Institute of Technology, the
Massachusetts Institute of Technology and the LIGO Scientific
Collaboration are set to make what they bill as a "status report" on
Thursday on the quest to detect gravitational waves. It is widely
expected they will announce they have achieved their goal.
"Let's say this: The first discovery of gravitational waves is a
Nobel Prize-winning venture," said physicist Bruce Allen of the Max
Planck Institute for Gravitational Physics in Hannover, Germany.
 "I believe in the next decade, our view of the universe is going to
change really quite dramatically," added Abhay Ashtekar, director of
Penn State University's Institute for Gravitation and the Cosmos.
Einstein in 1916 proposed the existence of these waves as an
outgrowth of his ground-breaking general theory of relativity.
"Gravitational waves are literally ripples in the curvature of
space-time that are caused by collisions of heavy and compact
objects like black holes and neutron stars," Ashtekar said.
'MOVING MASSES'
"They're waves, like light or any other kind of electromagnetic
radiation, except here what's 'waving' is space and time itself,"
said NASA astrophysicist Ira Thorpe, with the Goddard Space Flight
Center in Maryland. "You get radiation, basically light, when you
move some sort of charged particle. When you're moving masses, you
get gravitational waves."
Scientists have been trying to detect them using two large laser
instruments in the United States, known together as the Laser
Interferometer Gravitational-Wave Observatory (LIGO), as well as
another in Italy.
The twin LIGO installations are located roughly 1,800 miles (3,000
km) apart in Livingston, Louisiana, and Hanford, Washington. Having
two detectors is a way to sift out terrestrial rumblings, such as
traffic and earthquakes, from the faint ripples of space itself.
The LIGO work is funded by the National Science Foundation, an
independent agency of the U.S. government.
[to top of second column] |
All the current knowledge about the universe comes from
electromagnetic waves like radio waves, visible light, infrared
light, X-rays and gamma rays. But a lot of information remains
hidden because such waves get scattered as they traverse the cosmos.
That would not be the case with gravitational waves, making them an
enticing potential source of new information.
Two types of very massive and dense celestial objects, neutron stars
and black holes, have proven tough to study but could offer ideal
subjects if observations of gravitational waves are possible.
"People don't really know what's going on inside neutron stars,"
Allen said of these objects that weigh about 50 percent more than
the sun but are extremely compact, only about the size of a city.
"It gives us a detailed picture of what's happening inside or around
the object that's producing the waves. So, for example, if two black
holes orbit each other, we can't see it any way other than
gravitational waves because black holes don't emit any light, radio
waves, X-rays or anything. The only way to see that is through their
gravitational waves," Allen said.
Gravitational waves also offer a way to study what the universe was
like in its infancy. For the first roughly 200,000 years of its
existence, light did not travel freely through the universe, Allen
said, but "gravitational waves can travel freely, back to very early
times."
"So one cool thing is one day we'll be able to see what the universe
looked like in very early times using gravitational waves. That's
what actually got me interested in the field 25 years ago," Allen
said.
(Additional reporting by Irene Klotz in Cape Canaveral, Florida;
Editing by Tom Brown)
[© 2016 Thomson Reuters. All rights
reserved.]
Copyright 2016 Reuters. All rights reserved. This material may not be published,
broadcast, rewritten or redistributed.
 |
