The Royal Astronomical Society and the Institute of Physics in London gathered scientists from various countries to discuss the details of the impressively scaled new space expedition LISA. Gravitational waves predicted by Einstein's theory will be "caught" by three spacecraft separated from each other by five million kilometers.
A giant space instrument will orbit the Sun, lagging twenty degrees behind the Earth. This structure of three spacecraft positioned at the vertices of a triangle with sides of five million kilometers forms a plane turned 60 degrees relative to Earth's orbit. LISA will be one of the most alluring and expensive expeditions organized by humanity. It faces a serious task — to find the gravitational waves predicted by Einstein's general theory of relativity in 1916. Until now, no one has managed to measure them directly; only indirect evidence of their existence has been obtained.
Gravitational waves are emitted when very massive objects, such as black holes, rotate around each other or neutron stars collide at high speed. These invisible waves compress and stretch space-time as they travel toward us from distant parts of the Universe. They are not absorbed during their journey from the source, so scientists can study objects at very great distances and events that occurred immediately after the birth of the Universe.
The technologies needed to detect gravitational waves in space have been developed for many years by scientists in both Europe and America. The first equipment test (LISA Pathfinder) is planned for 2009.
To detect gravitational waves, researchers will measure the distance between the spacecraft using laser beams. By their reflection from test masses, it is possible to determine whether the structure of space-time is distorted. The measurement precision must be very high — down to ten picometers, one millionth of the diameter of a human hair!