What is the Einstein telescope, which will allow us to explore the "dark age" of the Universe

What is the Einstein telescope

It will be the largest gravitational wave detector ever built and will serve to push us to study the universe before the formation of stars

(Image: Einstein Telescope) The European strategy forum on research infrastructures (Esfri), responsible agency to indicate to European governments the priorities of scientific research, has just inserted the Einstein telescope, a huge detector of new generation of gravitational waves whose cost should be around 1.9 billion euros, in the road map of projects considered valid and to be pushed forward.

Although the operational phase is still quite far away at the moment, it is still a first step towards the actual construction of the instrument, which should be the largest gravitational wave detector ever built, equipped with a sensitivity up to 10 times higher than its predecessors and potentially able to help us seek the answers to the great still open questions of cosmology and physics, including the existence and nature of dark matter and energy and the reconciliation of general relativity and quantum mechanics.

What are waves gravitational

Short review of physics. Gravitational waves are a perturbation of space-time that originates as a result of the acceleration of one or more bodies with mass (two black holes or two rotating stars, for example), propagates at the speed of light and locally modifies the geometry of space-time itself.

Their existence derives directly from the equations of the theory of general relativity formulated by Albert Einstein over a century ago, but it was necessary to wait until 2015 to observe them directly: their effect is extremely weak, and therefore almost always hidden from other external disturbances. The detection of gravitational waves requires extremely sophisticated and sensitive measuring devices, the so-called interferometers, instruments capable of measuring the temporal discrepancy in the path traveled by two light waves.

In particular, an interferometer is a composite structure by two arms of equal length, one perpendicular to the other, to form an L. When a gravitational wave hits the instrument, the associated perturbation is expected to cause the light to take longer to travel one arm than the other. When the instruments register a time difference of this type, the warning of the possible passage of a gravitational wave is launched. To give an idea of ​​how weak these perturbations are, consider that interferometers must be able to detect a time difference equal to the displacement of the diameter of a hair over a distance between the Sun and Alpha Centauri, that is, over four light years.

The discoveries of interferometers

Despite these enormous difficulties, in 2015, as we said, the two interferometers of the aLigo experiment (by Hanford and Livingstone), whose collaboration also includes Italian scientists of the Virgo experiment, in Cascina, they managed to reveal the first gravitational wave signal ever detected by humans, emitted by two black holes that have merged with each other.

This first historical revelation was followed by others: two years later, the eyes of aLigo, Virgo and the Eso observatory in Chile again observed a signal of gravitational waves, generated this time by the collision of two neutron stars. In some ways, this was an even more important discovery, since, unlike black holes - which emit no radiation - neutron stars are accompanied by the emission of light radiation and heavy elements, including gold, platinum and uranium, and therefore provide a very precious mine of data useful for improving our understanding of the Universe.

The scientific community, far from paying, has continued to look ahead: in truth already in the 2004, more than ten years before the 2015 revelation, two scientists, the German Harald Lück, of the Max Planck Institute for Gravitational Physics, and the Italian Michele Punturo, research director of the Infn of Perugia, began to think of a detector of new generation, even bigger, more powerful and sensitive than his colleagues. The Einstein telescope, precisely.

"With the detectors we have today", says Punturo, who is co-chair of the management committee of the Einstein telescope and the Italian project manager, "we can see only a 'slice' of the Universe, at a relatively limited time distance. Current instruments have a physiological limit that does not allow us to look further than 8 billion years after the Big Bang [about 6 billion years ago, ed.]; the Einstein telescope, on the other hand, will allow us to push us to the so-called dark age, just 100 million years after the Big Bang, before the formation of stars ".

A triangle structure

The new detector, Punturo explains, will be a little different from the existing interferometers: it will have a triangular shape, rather than an L, and two interferometers will be placed at each vertex of the triangle, for a total of six "eyes". Currently, two possible sites for its construction have been identified: one in northern Europe, on the border between Belgium, Holland and Germany, and another in Sardinia, in an area with very low seismic activity and population density, which represents a significant point of strength because it minimizes the external "noise".

"The Einstein telescope - says the expert - will be multi-detector and multi-interferometer: in this way it will be possible to locate the source more precisely and decompose the signal into its polarizations. Sensitivity will also greatly increase, which will allow us to study signals in a much higher level of detail than what has been possible up to now, and in this way we can continue to test the theory of general relativity in increasingly extreme conditions. ", Which is important to understand if the theory has limits, what are these limits and if and how it can be reconciled with quantum mechanics.

" And to return to the themes of dark matter and dark energy - says Punturo - the Einstein telescope could help us learn more. There are theoretical models, for example, that predict that space-time, after the Big Bang, underwent quantum fluctuations that gave rise to non-stellar black holes, and these black holes could have something to do with dark matter. . The telescope will also be able to investigate the presence of any axion fields, another entity that could be linked to dark matter. And again: by characterizing gravitational waves more precisely, some modified theories of gravitation could occur that would make it possible not to introduce dark energy into cosmological models ". In short, there is a new physics to be discovered out there. “We have just entered a phase similar to that in which Galileo brought the telescope to his eyes - concludes Punturo -. And we can't wait to do it ”.


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Topics

Albert Einstein Physics Gravitational waves Space globalData.fldTopic = "Albert Einstein, Physics, Waves gravitational, Space "

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