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New Observatory will go a long way toward detectin
PHYSICS
New observatory will go a long way toward detecting gravity waves
ALL THAT might be standing between scientists and detection of gravity
waves is money.
Detection of the elusive gravity waves could be accomplished if the
National Science Foundation gets its request for $47 million for the
laser interferometer gravitational-wave observatory (LIGO) project.
Plans call for two buildings located at least 1,500 km (930 mi) apart.
The program involves researchers from California Institute of
Technology, Pasadena, and Massachusetts Institute of Technology,
Cambridge.
Success in the LIGO project could change how we view the universe and
commercial spinoffs could come from the technology developed in the
program, says Caltech's Rochus Vogt, the project's director.
"Gravitational waves, like radio waves in the 1950s and 1960s, may
create a revolution in our view of the universe and reveal unanticipated
signal sources," Vogt says.
The existence of gravitational waves, described as ripples in the
curvature of space-time, was postulated in Einstein's theory of
relativity. Gravity waves are entirely different from electromagnetic
waves.
While electromagnetic waves can be attenuated by Earth's atmosphere,
"gravitational waves come from all directions and penetrate everything,"
Vogt says. "The same thing that allows them to travel through everything
with impunity makes it very difficult to detect them, because they don't
interact with anything, including detectors."
The researchers plan to use extremely sensitive, stable lasers to detect
gravity waves. Each observatory will be L-shaped and contain two large
evacuated tubes perpendicular to each other with two pairs of freely
suspended masses at the end of each 4-km (2.5-mi) arm.
Laser beams will be aimed at the masses. If gravitational waves cause
even a minute separation of the masses, deflections of the beams will
register in a photodetector.
"The fantastic thing about these detectors is their precision," Vogt
says. "The prototype that has been developed is capable of a precision
of one part in [10.sup.18].
"Future advances should give us a factor of 1,000 times greater
precision, and ultimately our goal is a factor of 100,000 to 1 million
times better than the prototype," Vogt says.
"Eventually we expect to be able to detect movement of the masses on the
order of [10.sup.-16] cm, or about 1/100-millionth the diameter of a
hydrogen atom," he says.
Finding the wave source
The two-site Caltech-MIT LIGO might be able to detect the presence of
these waves, but it won't be able to pinpoint the source. A number of
other nations, most notably a British-German partnership and an
Italian-French collaboration, are planning to build similar facilities.
"These are independent programs, but the plans are being coordinated so
they will provide a worldwide network of detectors," Vogt says. "Gravity
wave detectors have very poor intrinsic directionality, so we use
several observatories together to triangulate the position of a source."
Physicists figure that some objects in space could emit signals in the
electromagnetic spectrum that are too weak for detection from Earth, but
might be strong emitters of gravitational waves. Thus, the new
observatories might provide data complementing conventional astronomical
information or offering completely new parameters.
If NSF funding plans follow the schedule, construction of the U.S. LIGOs
will be completed by 1995. The project team already is working on ways
of extending system performance beyond the prototype, including a joint
Caltech-Stanford (CA) Univ. advanced neodymium-YAG laser study.
This laser could find important commercial uses, Vogt says. One idea
involves using the laser in a projection technique for large-screen TV.
It also could provide better performance at certain wavelengths in
underwater communications.
MIT and Caltech now have extended their search for a site for LIGO
beyond California and New England.
"We're talking about a 4-km by 4-km building, so the terrain is very
important in terms of construction cost," Vogt says. "We want to find
the optimum sites from both cost and use standpoints."
PHOTO : Rochus Vogt of Caltech discusses plans for the laser
interferometer gravitational wave
PHOTO : observatory project. Physicists believe that this two-site
observatory and others planned
PHOTO : around the world will allow them to detect elusive gravity
waves.
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