Gravitational waves are one of the fundamental building blocks of our
developing picture of the universe. Although there is strong evidence for the
existence of gravitational waves, they have not yet been directly detected.
Gravitational
waves are thought to be similar to light waves in that they carry energy and
momentum that can be detected by a suitable instrument. Light carries
information about the structure of the matter that generated it, and scientists
think that gravitational waves will too.
It is believed
that gravitational waves behave something like ripples in the curvature of
space-time and are generated by the motion of massive particles. These waves
cause a varying strain of space-time, which result in changes in the distance
between points. If scientists can measure the changes that take place between
fixed points, more can learned about where these wave come from and what caused
them.
The Laser
Interferometer Space Antenna - LISA will attempt to detect gravitational waves.
The primary objective of the LISA mission is to observe gravitational waves
from distant stars. Of special interest are the gravitational waves generated
near the massive black holes found in the centers of many galaxies.
This mission
consists of three spacecraft flying 5 million kilometers apart in the formation
of an equilateral triangle. The triangle formation follows along behind the
Earth, in the same orbit, circling the sun.
The three LISA
spacecraft flying in formation will act as a giant interferometer, measuring
the distortion of space caused by passing gravitational waves. Each spacecraft
will contain two free-floating masses. Each mass is shielded from distorting
movements caused by the sun, or other factors, by its housing. Lasers in each
spacecraft will be used to measure with great precision the changes caused by
passing gravitational waves in the distance between the three
spacecraft.
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