UAntwerp plays a pioneering role in the realisation of the Einstein Telescope, with a huge structure being built underground to study gravitational waves. These waves are the key to unlocking the secrets of our universe.
Like a stone in a pond
Ever heard of gravitational waves? They are essentially waves in the curvature of spacetime. You can compare them to the ripples on the water when you throw a stone into a pond. The most likely cause of such gravitational waves is the merger of two neutron stars. These are dead stars that were more than three times heavier than our sun during their lifetime and now consist only of neutrons.
They are incredibly dense: one teaspoon of neutron star easily weighs over a billion tonnes. Every so often a pair of twin neutron stars occurs, with both stars orbiting each other extremely fast, culminating in a huge bang. This blast is so strong that it produces waves that can be detected across vast distances.
The same thing also sometimes happens with two black holes, in which case the blast is even more powerful. Because these gravitational waves are so enormous, we can detect them from very far away. The first time they were ever detected, in 2015, was 99 years after Albert Einstein had predicted their existence in his theory of relativity.
However, measuring them remains incredibly difficult. This is because the distance measurement is unfathomably small: about one ten-thousandth of a proton. Today, we only manage to observe a gravitational wave every few days. So there is a need for new equipment so we can measure more of them.
The ET will allow us to see much farther into the past of our universe, to the moment just after the Big Bang. We will be able to study the physics of black holes, for instance.
30 kilometres long, 270 metres deep
Telescopes that measure gravitational waves are different from those used to observe stars. They don't require clear skies – on the contrary, they are underground installations that rely on very precise lasers. The underground part is important, because this enables scientists to suppress natural and man-made vibrations.
The Einstein Telescope will be a giant new facility consisting of a triangular tunnel complex no less than 30 kilometres long, 270 metres underground. On each of the three corners will be a measuring station equipped with state-of-the-art lasers, suspended on long pendants averaging 15 metres in height. The ET is likely to be built at the tri-border point between Belgium, the Netherlands and Germany, but Sardinia is also a candidate. The final decision on the location will be made in 2026.
Black holes in Belgium
The project has garnered a lot of interest. It is backed by all five Flemish universities, and dozens of academic institutions and research laboratories from more than ten European countries are eager to support the project scientifically, politically and financially. The European Union has already set aside a significant budget for the Einstein Telescope, which is projected to cost approximately two billion euros.
That's a lot of money, but the importance of the Einstein Telescope can hardly be overstated. 'The ET will allow us to see much farther into the past of our universe, to the moment just after the Big Bang,' says Nick Van Remortel, co-coordinator of the project. 'We will be able to study gravitational waves in optimal conditions, but also the physics of black holes, for instance.'
In the meantime, the ETpathfinder is testing all the technologies. This prototype of the Einstein Telescope is already under construction in Maastricht, in a project co-founded by ... UAntwerp! The university is responsible for the construction of mechanical systems for the vacuum towers, the sensors and actuators for the seismic damping system, and the electronics of the data processing systems.
If all goes well, construction of the real telescope will start in 2026 and observations will begin in 2032. Things are looking good so far, because in 2021 the Einstein Telescope was included in the roadmap of the European Strategy Forum on Research Infrastructures (ESFRI). This is a sign of recognition of the project's great value, which strengthens the Einstein Telescope at the European level.
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