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Possible location for the »Grand« observatory in the Chinese Tienschan Mountains
Photo: GRAND Team
With unimaginable energy they hunt from the depths of space and neither galaxies, stars or planets can stop them.
Because neutrinos have no electrical charge and only a very, very low mass, they rarely come into contact with "normal" matter.
But if they do, then they can provide researchers with insights into the most extreme places in the universe.
Around two and a half years ago, a black hole in a galaxy several billion light-years away in the constellation Orion was identified as the source.
As a natural particle accelerator, it accelerates particles millions of times as fast as man-made facilities such as the Large Hadron Collider (LHC) near Geneva would be able to do.
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This is what a cosmic particle accelerator could look like
Photo: DESY / Science Communication Lab
Numerous experiments are carried out worldwide to search for high-energy neutrinos from space.
Researchers in China and other locations such as South America and Australia want to build an even larger neutrino observatory.
The “Giant Radio Array for Neutrino Detection”, or “Grand” for short, is to become a forest of antennas on a huge scale.
With its help, telltale radio signals should be listened to in the atmosphere, which neutrinos send through the atmosphere in the event of collisions.
The largest currently planned expansion stage of the plant would include 200,000 measuring devices on 200,000 square kilometers, i.e. on an area more than half the size of Germany.
The French astrophysicist Kumiko Kotera, she works at the Astrophysical Institute Paris and the Free University of Brussels, is one of the directors of the gigantic project.
And together with two colleagues, she has just published an article on the CO2 balance of the planned antenna network.
The manuscript has not yet been reviewed by colleagues, but it should be submitted for publication in a specialist journal.
“We really wanted to know what impact our planned project will have,” says Kotera, describing the motivation for talking to SPIEGEL.
"To our knowledge, nothing like this has yet been investigated in the field of astrophysics." Specifically, the authors consider the greenhouse gas emissions during the manufacture of the systems, the operation of the IT infrastructure and the climate balance of the trips the researchers have to make.
Everything was converted to the corresponding amount of CO₂.
A look at the article shows that the size of the project is decisive for the climate impact.
The authors examine three different stages of expansion:
A prototype of the observatory (»GrandProto300«), where 300 radio antennas are to be installed on an area of 200 square kilometers from this year on.
Total emissions: 478 tons of CO₂ per year.
A medium expansion stage (»Grand10k«), in which a total of 10,000 antennas will be distributed over 10,000 square kilometers by 2025.
Total emissions: 1061 tons of CO₂ per year.
The final expansion (»Grand200k«), during which a total of 200,000 antennas are to be installed at around 20 locations after 2030.
In total, they would be installed on an area of more than 200,000 square kilometers.
Total emissions: 13,385 tons per year.
To put it into perspective: Statistically speaking, every German emits 10.4 tons of CO₂ per year.
And a diesel car like the Mercedes C 220d has a total mileage of 250,000 kilometers and a total of 65 tons of carbon dioxide emissions, if you also take into account the manufacturing process.
At least that is how the Technical University of Eindhoven calculated it on behalf of the Green parliamentary group.
If you follow these figures, then only 200 cars would not have to be built and driven each year and mankind could, so to speak, afford the climate effects of the neutrio experiment.
That would of course not take into account the fact that the global economy is to become greenhouse gas neutral within a few decades.
Not all data will be saved
With the »Grand« observatory, the various areas - digital infrastructure, travel, technical systems - are of different importance for the overall bill, depending on the stage of expansion.
Most of the stresses in the area of computer technology come together in the prototype version.
A total of 69 percent of emissions are caused by the use of supercomputers from various universities, the manufacture of laptop and desktop computers, the storage of the resulting data, video conferences and emails.
Travel accounts for 27 percent of emissions, and measuring devices only 4 percent.
It looks completely different with the maximum expansion stage, here the equipment would be responsible for 48 percent of the total load, travel only for 7 percent.
After all, the digital sector would provide 45 percent of emissions.
"All in all, we found it surprising what a great role digital technologies play as sources of greenhouse gases," says Kotera.
The team now wants to draw practical conclusions from the findings.
Among other things, it is about the question of which huge amounts of data actually have to be stored.
"We definitely can't keep everything," says Kotera.
The problem is already known from radio astronomy.
One now hopes for clever strategies for data management from this area.
The study also offers an amazing idea for the transfer of mountains of data: For the environment, it might make more sense to send storage media by airmail than to send the many petabytes of information over the network.
"The paper is very interesting for the entire community."
Victoria Grinberg, astrophysicist at the University of Tübingen
»The balance sheet makes sense, the assumptions seem plausible.
The paper is very interesting for the entire community, «said Victoria Grinberg from the University of Tübingen, commenting on the studies by Kotera and her colleagues.
The astrophysicist was not involved in the evaluations, but is involved in "Astronomers for Planet Earth", a worldwide network of climate-interested astro researchers.
The topic of climate protection is becoming more and more important in the community.
This is also shown by several publications from last year.
The journal "Nature Astronomy" has dealt with the question of how much greenhouse gases are generated simply by the fact that astronomers regularly travel to large conferences in different parts of the world.
Result: An online meeting produces less than a thousandth of the carbon dioxide emissions of a classic on-site meeting.
Australian researchers have added up all the emissions they generate.
Accordingly, more than 40 percent are above the average in their country - which is already quite high by international standards.
The Max Planck Institute for Astronomy in Heidelberg has issued a comparable calculation for its around 320 employees.
The first author of this research paper was Knud Jahnke.
If you ask him about Kotera's work, he too expresses himself positively.
For individual aspects, details can certainly be discussed, such as the power consumption used for data transfer.
"Overall, I think that's an extremely good example of how every project should do it," says Jahnke.
Only when such data is available, says Jahnke, can one see where measures to reduce emissions make sense - and which ones should be tackled first, given a limited budget of time and money.
Researcher Kotera says she was worried at first when the calculations on the climate impacts began.
But the feedback from the research network was very positive.
"Besides, we thought that sooner or later this question would have come up to us anyway."
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