To better understand the structures observed in the universe, scientists use computer simulations that are then compared with what we see in the sky: each simulation aims to study a specific phenomenon.
In Geneva, astrophysicist Ann Verham and her group are participating sphinxa very useful simulation for describing very distant galaxies.
One example among many is The IllustrisTNG Project. Its calculations rely in particular on the laws of nature, the expansion of the universe, the gravitational pull of matter on itself, the motion of cosmic gas, as well as the formation of stars and black holes.
All of these components and physical processes are modeled after the initial conditions that resemble a very young universe: from the moments after the Big Bang, to the present day. This represents more than 13.8 billion years of cosmic evolution in three dimensions.
>> Simulation of a single galaxy traced back in time by IllustrisTNG:
The simulated volume contains tens of thousands of galaxies captured in fine detail, covering a wide range of masses, star formation rates, shapes, and sizes, whose characteristics match well with the number of galaxies observed in the real universe.
As for Euclid, he makes use of his own dedicated program called flagship simulator“The largest cosmic simulation ever performed in the world,” Stefan Baltani specifies. It was implemented by the University of Zurich in Lugano, at the very strong Swiss National Center for Scientific Computing (cscs): “The large size makes it possible to make statistics or search for rare objects,” the cosmologist notes. The University of Geneva professor and his team participated in the design and manufacture of VIS, one of Euclid’s instruments.
>> Visualization of Euclid’s leading simulation:
The program is specifically designed based on what scientists want to study: “We are looking for large-scale structures, as well as the presence of dark matter and dark energy. In the simulation, we were able to overlook ordinary matter: we persuaded ourselves to ‘draw’ galaxies in places of great density.” of dark matter while respecting the mass, color, etc. distributions of the observed galaxies. All this in order to be able to make a simulation of the entire universe, and not just a very small part.
>> Euclid will paint the sky at different times:
>> Watch at 7:30 p.m. “The Euclid Space Telescope Will Help Study Dark Matter in the Universe”:
Euclid will draw a three-dimensional map of the universe, including two billion galaxies on a portion of just over a third of the celestial vault, which is a huge portion. It will also go back in time up to 10 billion light years. These unprecedented maps aim to reconstruct the history of the universe “in timescales,” according to astrophysicist Yannick Millier of Euclid Union.
>> An excerpt from Euclid’s groundbreaking simulation, From the present local universe (left) to when it was about 3 billion years old (right), when galaxy clusters first started to form:
Central galaxies, which inhabit the center of dark matter halos, are in blue. Satellite galaxies, in the most massive halos, appear at the highest intensity peaks of the underlying dark matter, in red. Time flows from right to left in this image. [J. Carretero (PIC), P. Tallada (PIC), S. Serrano (ICE) and the Euclid Consortium Cosmological Simulations SWG – Euclid/ESA]
Alice Gasparini explains in La Matinale that Euclid’s observations “will create an image of the galaxies that will arrive to us, slightly distorted by the presence of matter between us and these observed galaxies.” “Dark matter ignores light. We have no way of observing it except through gravity and the effect of this matter on space-time. This is the effect of gravitational lensing: the light that comes to us from galaxies observed by the satellite is affected by this distortion of space-time.” For her, what is important is that “this satellite will also examine the evolution of this effect over time.”
>> Visualization of space-time distorted by a massive body:
The distribution of matter actually evolves over millions and billions of years. The scientist defines: “Matter is a form of energy, but in the universe there is also another form of energy, which is dominant and this form has the opposite effect to the effect of matter: it is dark energy.” It will be responsible for the accelerated expansion of the universe. Thanks to Euclid’s observations, cosmologists will be able to sort out the various theories that explain these phenomena.
>> Explanations by Alice Gasparini, Doctor of Theoretical Physics and Science Education specializing in Cosmology:
In this, Euclid would test gravity describing the motions of all celestial bodies on the scale of the universe and check if there was no alternative gravity, called “modified”, which would function without dark energy.
“Einstein’s theory of general relativity is the theory that best describes large-scale gravity; however, observations indicate that there is an important gravitational factor that we miss. We can solve this problem by saying that there is matter that we don’t see and that adds an element to the universe… It’s an existential solution. But we can also To say, in fact, on a very, very broad scale that there is a ‘more general’ theory than general relativity.”
“Physicists are looking for exotic particles that could make up dark matter, while in mathematics, theoretical physicists are working hard on equations to see if there is a larger theory that includes Einstein’s,” notes Carol Mundell, director of science at the European Space Agency. , met in Florida for the launch of Euclid. “The special case of Einstein’s theory is Newtonian gravity: For 350 years, Newton’s laws of gravity have been what we thought were right. And they work for our everyday lives. Then Einstein came along and said, ‘Uh, but if we go for larger velocities or masses, we have a bigger theory’.” Including Newton in physics, one tries to understand if there is a larger theory for which Einstein’s general theory of relativity is a special case, so we’re always pushing those boundaries theoretically, technologically and scientifically,” she notes in Tout un Monde.
>> Listen to Tout un Monde about Euclid’s task:
Everything we know comes from the general theory of relativity developed by Albert Einstein 1915Describes how matter and energy modify the geometry of space-time. His equation shows that gravity is not a force acting between two bodies – this is the traditional definition of gravity according to Newton – but manifests itself through the curvature of space-time. The curvature which is actually the gravitational field of the massive body that generates it.
Einstein’s predictions have been proven correct by experiments: yes, the universe is indeed expanding, black holes do exist, just as gravitational waves propagate through space-time. These are the three proven pillars of general relativity. Euclid will make it possible to sort out existing theories thanks to a map of the extragalactic sky.
>> E = MC2A real revolution in physics:
The famous equation “E = MC2″—energy equals mass times the speed of light squared—appears in a manuscript written by Albert Einstein in 1912. This 72-page manuscript is the first in which a physicist reveals his theory of relativity. [AP Photo/Sotheby’s – Keystone]
“Going into space, it is possible to improve what we can do on Earth thanks to the very stable quality of the image that we will get from these billions of galaxies. It is not just a matter of the experiment itself, which will investigate our cosmic history, more than 70% of the age of the universe. …which in itself is amazing to me,” rejoices Gaitee Hussain, head of the scientific department at ESA. “But there is also a lot of additional, additional science that will come out of it because scientists are very creative. We will find all kinds of satellite galaxies, galaxy clusters, and there will be a lot of other scientific discoveries that we can’t even think about today,” predicts the person who also made the trip to the Cape. Canaveral.
>> Watch at 7:30 PM with Professor Camille Bonvin (UNIGE), “Dark matter discoveries will provide new insight into the universe”:
“It is only now possible to study the properties of the universe on very large scales,” says Professor Martin Kunz (UNIGE), the Swiss curator of Euclid. “In cosmology, we always start from a model and the Standard Model says the universe is completely isotropic and completely homogeneous, so it’s the same everywhere and in all directions. But obviously, we also have to check that,” he said. Towards the shooting ranges in Merritt Island. He is pleased with Euclid’s accuracy, which will be able to characterize the universe in a much finer way than anything achieved so far, with a quality close to that of Hubble: “A treasure trove of data astronomers will be able to dig for decades to come and find incredibly exciting stuff!”
>> Explanations of Professor Martin Kunz (UNIGE), specialist in theoretical cosmology and responsible for Euclid’s Switzerland:
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