New plans for a revolutionary observatory
Scientists of the FOM Institute for subatomic physics Nikhef are closely involved in the design for Einstein Telescope: Europe's next-generation detector that will 'see' the universe in gravitational waves. Gravitational waves are minute ripples in the fabric of spacetime, which are predicted to emanate from cosmic catastrophes such as merging black holes and collapsing stars and supernovae. This detector will offer the potential to probe the earliest moments of the universe, just after the Big Bang. The design will be presented at the site of the European Gravitational Observatory (EGO) in Pisa, Italy.
Like earlier detectors, the Einstein Observatory will be based on the measurement of tiny changes (far less than the size of an atomic nucleus) in the lengths of two connected arms several kilometres long, caused by a passing gravitational wave. Laser beams passing down the arms record their periodic stretching and shrinking as interference patterns in a central photodetector. But this detector will be a hundred times more sensitive than its predecessors. This can be achieved by building ET underground, at a depth of about 100 to 200 metres, to reduce the effect of residual seismic movements. This will enable higher sensitivities to be achieved at low frequencies, between 1 and 100 hertz (Hz).
Multi-detector
The strategy behind the ET project is to build an observatory that overcomes the limitations of current detector sites by hosting more than one gravitational wave detector. It will consist of three nested detectors, each composed of two interferometers with arms 10 kilometres long. One interferometer will detect low-frequency gravitational wave signals (2 to 40 Hz), while the other will detect the high-frequency components. The configuration is designed to allow the observatory to evolve by accommodating successive upgrades or replacement components that can take advantage of future developments in interferometry and also respond to a variety of scientific objectives.
Theory of gravitation
Jo van den Brand (Nikhef), leader of a workgroup in ET: "The Einstein Telescope will open up a new window in our universe by directly detecting the ripples in spacetime that are generated by the universe's most energetic objects and events. This will provide significant opportunities for exact measurements of the effects of strong and dynamic gravitational fields. Such measurements will expose every possible shortcoming in the highly robust and successful framework of Einsteins's general theory of relativity and will point us in the direction of the real theory of gravitation, which will unite the principles of relativity with those of quantum mechanics. As gravitational waves penetrate all areas of space and time virtually unweakened, ET can measure waves that originate from areas with the highest material density, the earliest stages of the Big Bang and the most extreme curves of spacetime."