Flemish universities bid to build the Einstein Telescope

Summary

Flemish and Dutch universities are collaborating on a proposal to develop a gravitational wave observatory, but they have to beat Sardinia to get it

Cosmic wonder

Plans to build a gravitational wave observatory in the Limburg region were presented this week in Antwerp. While the facility would probably be built on the Dutch side of the border, Flemish universities are closely involved in the project, which aims to expand our fundamental understanding of the universe.

Gravitational waves are ripples in space-time, caused by violent events such as stars collapsing or black holes colliding. Albert Einstein predicted their existence in 1916 in his general theory of relativity, but it was not until 1974 that indirect evidence was found to support his prediction.

Another 41 years passed before the first direct observation of gravitational waves, an achievement that earned three of the scientists involved the Nobel prize for physics in 2017. Gravitational waves are both very feint and very fast, which means detectors have to be highly sensitive in order to pick up the changes caused when the waves wash over our planet.

Feint and fast

The method that won the Nobel prize involved building two four-kilometre-long tunnels at right angles, in an L shape. Laser beams fired down each tunnel were bounced back from a mirror at the far end.

If a gravitational wave is passing, it stretches – very, very slightly – in one tunnel more than the other, which means that one laser beam arrives back fractionally later than the other. Measuring this difference allows you to “see” the gravitational wave.

The longer the tunnel, the more sensitive the detector, so the new project – called the Einstein Telescope – would involve a detector with three 10km tunnels arranged in a triangle. This should make it 10 times more sensitive than its predecessors, allowing it to observe cosmic events that were previously invisible.

The region’s assets include the right topsoil and a high density of research staff

The other challenge of gravitational wave detection is screening out movements and vibrations that could interfere with the laser beams. To this end, the Einstein Telescope would be built 200 to 300 metres underground, taking advantage of the hard rocks and damping topsoil of the Limburg region. There are also few railway lines and little heavy industry in the area to produce vibrations.

The region’s other asset is the high density of universities that can be called upon to staff and operate the telescope. KU Leuven and the universities of Ghent, Antwerp and Hasselt are all involved on the Flemish side of the project, while Dutch participants include the National Institute for Subatomic Physics and the universities of Maastricht and Eindhoven.

To compile the bid, the partners are building a research facility in Maastricht called the ETpathfinder. “This infrastructure is expected to grow into an international centre for research on gravitational-wave astronomy, high-precision measurement techniques, seismic isolation, measuring and control software, cryogenic technology and optics,” said Nick van Remortel, professor of physics at Antwerp University.

ETpathfinder will be financed by the EU’s Interreg programme, with contributions from the Dutch and Flemish governments and the provinces and universities involved. The observatory itself will be funded by the EU, with the Italian island of Sardinia also competing for the honour of hosting it.

The winning bid will be announced in 2021. If the Einstein Telescope is successful, construction could start by 2025, with the first observations in 2032.

Image: The Flemish-Dutch design for the Einstein Telescope