It seems a little strange, a plan to put a new telescope 200 meters underground. But the Einstein telescope, as the kilometer-wide measuring instrument will be called, is not a telescope in the traditional sense, it is a telescope that points to the sky and collects light from distant planets and stars.
Instead, when it ends in the second half of this decade, it will look at what are called gravitational waves. These vibrations arise in space and time when two heavy objects, such as black holes, collide in the universe.
These waves were first measured in 2016, using the Ligo Gravitational Wave Telescope in the United States. In addition, Europe has such a detector, Virgo, near Pisa, in Italy. The pioneers behind this first measurement won the Nobel Prize in Physics in 2017.
A new window on the universe
“Gravity waves are opening a whole new window on the universe,” says physicist Jo van den Brand, Einstein Telescope project manager. Until now, everything we could see in the universe – whether it was visible light or thermal radiation – was physically similar. All are forms of electromagnetic radiation. With gravitational waves, it is as if you can suddenly not only see the universe, but also hear it.
Einstein’s telescope will soon be able to “hear” three underground arms, each 10 kilometers long, as lasers constantly bounce back and forth between the mirrors at their ends. When the gravitational wave passes, it kneads the detector’s arms slightly, alternately making them slightly shorter and longer.
To be able to notice this, the environment should be calm, without disturbing the vibrations, for example. That is why the telescope will soon be deep underground, with a stable bottom protecting the instrument. Previous soil measurements have already shown that the Limburg soil is uniquely suited for this indeed.
The group after the big bang
The Einstein telescope also promises to be much more powerful than its predecessors. For example, it can pick up a thousand times more vibrations from the universe than the current generation of devices. “You can also look deep into the universe with Einstein’s telescope, even a fraction of a second after the Big Bang,” says van den Brand. “With the best regular telescopes, even a new and powerful space telescope like James Webb, you can see no more than 300,000 to 400,000 years after the Big Bang, when the universe was much older.”
There are theories about how the universe was built during its first moments, but they are still impossible to verify. “Actually, nobody knows exactly what we’ll see,” says van den Brand. “This is the most exciting.”
The 42 million that the Cabinet is now allocating through the National Growth Fund will help in the start-up phase, including research and hiring people. The largest amount is for the actual construction of the telescope, when it comes to the Netherlands. Limburg is still in competition with Italy, which has nominated the Sous Inatus mines in Sardinia as a construction site. The final decision will be made around 2025.
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