Einstein Telescope: The Next Wave in Gravity Science

How Gravitational Waves Are Detected (Interferometers 101)

The history of astronomy is closely tied to the progress of telescopes, which have progressively revealed more of the Universe to us. It began with the primitive telescope of Galileo and other pioneers, and continues to this day.

As time passes, more and more ways of detecting stellar activity have been deployed beyond the visible light spectrum.

We have covered several such new telescope megaprojects, for example:

• DKIST, the world’s most powerful solar telescope.
• The James Webb Space Telescope, located millions of miles away from Earth.
• The Vera C. Rubin Observatory, a survey telescope looking at the entire sky all at once.
• SKAO (Square Kilometre Array Observatory), studying the sky in the radio wave spectrum.
• DUNE (Deep Underground Neutrino Experiment), detecting elusive neutrinos.
• ELT (Extremely Large Telescope) for ultra-strong magnification

Another new type of astronomy is emerging, one that studies the sky in an entirely novel fashion: instead of light and various wavelengths of electromagnetic waves, it measures gravitational waves.

Only theoretical until relatively recently, now gravitational waves are a proven phenomenon.

We previously covered such “gravity telescopes” with the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Kamioka Gravitational Wave Detector (KAGRA).

These early 2^nd generation of gravity telescopes have not only demonstrated the existence of gravitational waves, but also helped with the detection of more than 200 gravitational waves already. They also showed that this entirely new form of astronomy can be done in multiple ways, either through a large-scale project (LIGO) or ultra-precise measurement protected from interference (KAGRA).

The next generation is most likely to combine large-scale and low interference to go one step further.

This is the idea behind the Einstein Telescope, a European project proposed for the third generation of ground-based gravitational wave (GW) detectors.

From Einstein’s Theory to Gravitational Waves

Gravity had long been believed to be “just” one of the Universe’s fundamental forces, like electromagnetism or the force driving nuclear forces at the atomic level.

But at the turn of the 20^th century, Einstein’s theory of relativity described gravity as the curvature of space-time.

His theory not only correctly described how gravity works for very large objects like stars, but also predicted many space phenomena yet to be discovered at the time, like neutron stars and black holes.

Another prediction was the existence of gravitational waves, causing space to stretch and squeeze like ripples propagating on the surface of a lake.

Unlike a regular wave of light or even an ocean wave of water, a gravitational wave is not carried by any particles.

Instead, a gravitational wave occurs when the fabric of space-time itself waves or vibrates.

So, gravitational waves essentially cause a specific segment of the universe to stretch or contract, thereby making a given distance longer or shorter as they pass by.

Some astronomical events would be likely massive enough to generate gravitational waves strong enough to be measured, like, for example, the collision of two black holes.

However, no matter how powerful such a phenomenon is in absolute terms, the massive distance between Earth and its source, and the difficulty of trying to measure space-time itself, mean that an ultra-sensitive instrument needs to be designed to detect these events.

By the time the gravitational waves reach Earth, millions or billions of light-years away, they are thousands of billions of times smaller.

So you need highly precise measurements, as the amount of space-time wobbling the gravitational waves generated is going to be 10,000x smaller than the nucleus of an atom!

How Interferometers Detect Gravitational Waves

The first indirect evidence of gravitational waves was obtained through the study of a binary pulsar’s orbit. The orbital decay energy loss matched the predicted energy that would be lost to the generation of gravitational waves, winning the scientists in charge of this discovery the 1993 Nobel Prize in Physics.

Source: Nobel Prize

Direct measurement required a different type of proof, using an interferometer. The basic idea of an interferometer is to use the interaction between beams of light. If two light waves have the same wavelength, they’ll overlap and create a pattern of dark and bright spots.

But if something changes the distance traveled by these wavelengths, like a gravitational wave, the disturbance can be measured.

As the expansion and contraction of space-time from gravitational waves also expand and contract one of the arms of the interferometer more than the other, this creates a detectable and measurable effect of gravitational waves.

Einstein Telescope: Design, Timeline, and Location

Third-Generation Design: Longer Arms, Lower Noise, Higher Power

KAGRA, LIGO, and other 2nd-generation gravitational wave detectors are expected to reach their technical limits by the end of the decade.

This is especially true for low frequencies, for which current detectors are fundamentally limited by seismic noise. This is true even for KAGRA and its ultra-cold temperature and underground location, which are looking to help with that problem.

One way to reduce the risk of seismic noise interfering with the measurement is simply to make the proper signal that much stronger.

It can be achieved primarily with two methods:

• Using longer arms for the telescope.
• Using more powerful lasers.

Einstein is looking to do both, while also applying the same method as KAGRA, underground location and ultra-cold temperature, to reduce all interference, like thermal noise.

From ESFRI to ET Collaboration: 2021–2035 Roadmap

The Einstein Telescope was formally added to the European Strategy Forum on Research Infrastructures project list in 2021, with the Einstein Telescope Collaboration founded in 2023.

By 2025, the Einstein Telescope will have been integrated at the level of individual European countries, notably the Netherlands, Belgium, Germany, France, and Italy.

A decision on the location of the telescope is expected for 2026-2027, with construction starting in 2028. The first observation is expected for 2035.

Source: Einstein Telescope

Triangular 10-km Arms, 250–300 m Underground

The Einstein Telescope will consist of three 10-kilometer tunnels, each of a 6.5m width (21 feet).

Source: Einstein Telescope

The 3 tunnels will form an equilateral triangle with interconnected laser emitters, mirrors, and light detectors.

Source: Einstein Telescope

The telescope will be built deep underground, up to 250-300 meters deep (820-985 feet), allowing it to be undisturbed by surface activities and dampening any surface seismic movements.

Access will be managed through a vertical access shaft, with a larger room being built to host the instruments, power supply, and local control offices for the scientists working on the project.

Source: Einstein Telescope

The underground location is helpful in reducing the impact of the telescope on its surroundings, considering the size of the project.

Above ground, hardly anything will be visible of the observatory.

The Einstein Telescope will detect a thousand times more gravitational waves than its predecessors, measuring changes in distances 10,000x smaller than the nucleus of the smallest atom.

Candidate Sites: EMR, Sardinia, and Lusatia (Germany)

The location for the telescope is still undecided, and will ultimately depend on the participating countries and the negotiations between them to decide who will ultimately host the project.

So far, it seems that the most likely option is the Eurégio Meuse-Rhin region, bordering the Netherlands, Belgium, and Germany. With this site being at the corner of 3 of the major contributors to the project, this seems like a good political compromise, even if it leaves Italy out.

In addition, the region has interesting geological features that should help its case as a potential site:

• The deep underground layer is hard enough not to move much, and seismic activity is relatively limited in that area.
• The top layer of soil is very soft, absorbing most of the man-made vibrations from industries and transport.
  • In addition, the region is not very affected by some of the most troublesome activities for gravitational waves telescopes, like metallurgy, heavy industries, railroads, or wind turbines.

The hard surface combined with the soft, cushioning top layer seems ideally suited for the Einstein Telescope.

Lastly, the region has good infrastructure (including nearby international airports) and is in close proximity to many high-tech industries and universities, making it an easy site to relocate for scientists and for the construction to find qualified industrial suppliers.

Reading out and working with the underground equipment can be done remotely from the surrounding existing scientific institutes and campuses.

Alternative locations that are also discussed include the Italian island of Sardinia and Lusatia in the German state of Saxony.

Wherever the telescope is built, the preparation and later construction will generate orders for industry and more than 1,500 direct and indirect jobs.
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Einstein Telescope Goals

Einstein’s general theory of relativity

As its name indicates, one of the main goals of this telescope will be to test and study Einstein’s general theory of relativity, which describes space-time more as a flexible and stretchable fabric than a fixed characteristic of the Universe.

In that theory, gravity is the bending of space-time itself, hence it predicts gravitational waves as well.

Still, gravity is maybe the least understood of the physical forces in the Universe, and many gravity theories exist. So the Einstein Telescope might help at least point to which are more likely to be true.

Cosmology

By being able to analyze ultra-large-scale gravitational waves that are very small in their intensity, the telescope will be able to analyze the large structure of the universe.

It will also be able to detect gravitational waves from the early phase of the Universe, when it was expanding very quickly.

Source: Einstein Telescope

Warning Of Observable Events

Gravitational waves travel through the Universe as fast as possible, being absolutely not hindered by matter.

So it could give early warning of celestial events to which to turn toward electromagnetic, light, or neutrino telescopes just when these signals will hit Earth.

Cataloguing Supermassive Stars

This telescope can detect objects that emit little to no other signals, as long as they are massive enough to create gravitational waves.

So it is likely it will detect many new black holes, neutron stars, and other ultra-dense stars that were previously unknown.

Neutron-Star Physics

Neutron stars are so dense that they are entirely made of neutrons, instead of normal atoms. This is essentially the last stage before a star becomes so dense that it turns into a black hole.

Matter at this extreme of density and gravity is still poorly understood, and analysis of gravitational waves from neutron stars might elucidate what is happening in them at the subatomic level.

Key Engineering: Lasers, Cryogenics, and 130 km of UHV

New Lasers & Mirrors

Due to the increased power requirement, the telescope will not be able to use the more conventional laser source at a wavelength of 1064 nm. Instead, new lasers must be developed that operate at wavelengths of 1550 nm or 2090 nm.

The implementation of novel quantum technologies, such as squeezed light sources, could be one of the many innovations required by this project.

The longer distance crossed, the more extreme the precision required, necessitating perfect mirrors. Most importantly, they must keep the wavefront distortions from thermal effects minimal, low amplitude, and phase noise with stable pointing accuracy.

Improving the quality of the mirror substrate, polishing, and coatings to reduce optical losses is an area where academic and industrial expertise in advanced materials and precision manufacturing is critical.

130 km Ultra-High Vacuum Network

Like other gravitational wave detectors, a strong vacuum will be needed to keep air or any particles from interfering with the laser light and giving a false signal.

The size of the installation, however, brings this question to a new level. It will require 130 kilometers of ultra-high vacuum tubes (1 meter, operating pressure < 0.0000000001 mbar).

The mirrors themselves are suspended in 10 – 20 meter high vacuum towers with a diameter of 3 to 5 meters.

10–20 K Cryogenics and Seismic Isolation

The cryogenic plant is required for keeping the mirrors at a temperature as low as 10ºK (-263 ºC / -441ºF). But the same cooling system creates its own vibration that must not be transmitted to the 200 kg mirrors.

So the heat sink needs to be exclusively made of low-stiffness links, taking away heat generated by the impact of the laser beam through both conduction and radiation.

Similarly, the high sensitivity of the instrument is only achievable if any outside vibrations not due to gravity are blocked.

So vibration dampers must isolate the installation from all sources of disturbances, in particular from seismic movements. Horizontal, vertical, and rotational vibrations must be reduced through active and passive control.

Big-Data & AI for Overlapping Signals

At any moment, the Earth is crisscrossed by an unknown number of gravitational waves. And the smaller the detectable wave we can detect, the more we can detect at once, with each signal entangled with the others.

This means that not only the Einstein Telescope will generate a massive amount of scientific data, but that innovations in data analysis techniques will be needed to analyze separately overlapping gravitational waves.

Collaboration with experts in big data, cloud computing, and AI could lead to more efficient data management and analysis tools.

Conclusion

While the first generation of gravitational wave telescopes proved they exist, and the second, like advanced LIGO and KAGRA, gave us new data about the Universe, they are still relatively early prototypes testing the mere concept of this technology.

The lessons learned can now all be integrated into a single telescope, which is the goal of the Einstein Telescope. It will use both the extra-long arm and vacuum tubes of LIGO, and the cooling & underground location of KAGRA.

The progress in laser, mirror production, engineering, and AI-driven data processing can now also be integrated into the concept from the beginning, instead of being added as upgrades to a design not initially made for them.

This will radically change how gravity and the Universe at large can be studied.

A project like this might at first glance appear purely academic. This is rarely the case, even if the direct applications are hard to imagine initially.

For example, Einstein’s theory of relativity is today routinely used to calibrate GPS satellites, an everyday application that was difficult to foresee in 1919 when it was first published.

Similarly, projects like this one are pushing scientists to invent ever more precise mirrors, stabilization and cooling systems, and lasers, demanding world-class levels of engineering.

These innovations are likely to bear fruit in technologies well beyond astronomy, including advanced computing and space systems.

Investing in Advanced Optics

Corning Incorporated

As telescopes push what is possible in terms of precision manufacturing of advanced glass, this also opens many industrial possibilities in sectors as varied as automotive, semiconductors, AI, defense, biotech, healthcare, etc. The advanced optic market is a $310B market, expected to grow by 9.2% CAGR until 2032.

Corning is a glass and optics company that has existed for 170 years. Over its history, it has produced the first glass bulbs for Thomas Edison’s electric light, the first low-loss optical fiber, the cellular substrates that enable catalytic converters, and the first damage-resistant cover glass for mobile devices.

Source: Corning

Today, the company is focused on core technologies related to manufacturing glass and ceramics, as well as optical physics technologies, which share common manufacturing processes and end markets.

Source: Corning

This interconnection of technologies allows the company to share common manufacturing, research, and engineering capabilities between its different product lines. With 52,000+ employees, 77+ manufacturing sites worldwide, and 10+ R&D facilities, the company is a large player in its niche.

Source: Corning

The company is benefiting from the boom in AI and data center building (optical fibers), as well as the overall consumption of specialty glass in screens and biotechnology.

Corning should not be impacted much by tariffs, as 90% of US revenues come from products with a US origin. Very little of the sales made in China originated from US facilities, with 80% of Chinese sales made in China.

Tariffs could even help, as Corning is entering the solar panel market, with the strategic control of Hemlock Solar, to produce US-made panels, as Asian solar panels (not just Chinese) are being submitted to quadruple-digit tariffs. 80% of the capacity has already been secured by customers’ commitments.

Solar makes a lot of sense for the company, with silicon handling a core manufacturing expertise of the company, having produced polysilicon for 60 years, including ultra-pure silicon (99.9999999999% pure) and now launching production of silicon wafer, a product imported at 100% in the USA.

Source: Corning

The company is also looking at other advanced technologies where its expertise in glass and ceramics could provide a solid edge, including bendable glass, AR, carbon capture, etc.

Source: Corning

Overall, Corning is a highly technical company with localized manufacturing that should not be affected by deglobalization. It also embraces new markets that match its core competencies, notably solar and optical communication / AI infrastructure. This makes it both a relatively conservative company, only digging deeper into its niche, but also a potential growth stock in high-tech markets.

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