Albert Einstein predicted their existence in the last century, but thought it would be impossible to discover them. Astronomers are now looking for them, nevertheless: gravitational waves. They are thought to distort space-time, which then behaves like a rubber mat that is compressed and stretched. It is assumed these waves are triggered by cosmic catastrophes, such as the explosion of a massive sun (supernova) or the collision of black holes. But even quakes which are not all that powerful are believed to generate gravitational waves. Two astrophysicists observed a pair of pulsars - densely packed, burned-out stars - circling each other and discovered that the two partners are coming increasingly closer to one another. It seems that this duo is constantly losing energy, which it emits in the form of gravitational waves. This discovery was awarded the Nobel Prize in 1993.
For some years now, researchers have been looking for this phenomenon directly with the aid of sophisticated instruments. One of the detectors can be found in Ruthe near Hanover and goes by the name of GEO 600. Laser light is split into two beams by a semi-transparent mirror and speeds through two 600-metre tubes set into the ground. Reflections at further mirrors cause the two beams to meet up again and form a specific optical pattern. If a gravitational wave races across the array, the space between the mirrors will be distorted, and the pattern will suddenly flicker briefly.
Although there has been no sighting thus far, the work of the gravitational wave hunters at the boundaries of modern physics is exciting. The film looks over their shoulders and explains what the ripples of space-time mean - and why they could open up a new window into space one day.