It is often said that it was Edwin Hubble who discovered the expansion of space, confirming a prediction of Einstein's general theory of relativity. However, the reality is actually somewhat different. What Hubble did was to show clearly that there is a proportionality relationship with a constant between the spectral redshift of galaxies and their distance from the Milky Way. For him, an excellent observer but by no means a theorist, this shift was a simple Doppler effect.
In fact, it was Georges Lemaître who not only discovered the law with the constant now called Hubble-Lemaître before Hubble, but also understood and showed that this law is based on the expansion of the wavelength of a photon during its journey to our detectors in our country Telescopes. The longer this journey had lasted, the more room there was to expand. We can also show that this constant, which is in some sense a measure of the rate of expansion of the observable cosmos, varies over time at some point in its history.
By observing fossil radiation, the oldest light in the universe, the Planck satellite has provided us with data that select a possible solution to the equations of cosmology. We derive the laws of evolution of the Hubble constant, which allow us to calculate the one we observe today.
Two different measurements of the rate of expansion of the universe
For several years now, as cosmologists say, there has been a growing tension between this value, predicted from very carefully analyzed data by Planck, and the measurement of the Hubble-Lemaître constant, derived from the study of supernovae over the last billion years led to the discovery of the accelerated expansion of the observable universe since that time.
We don't know exactly how to interpret this disagreement, since the two methods have been carefully tested and proven to be reliable and error-free (although we remember that the same was also true of data that seemed to prove that neutrinos travel faster than can be light). ).
In this video, Nobel Prize winner Dr. Adam Riess the phenomenon known as “Hubble tension” and the importance of this puzzle for our understanding of the universe. To get a reasonably accurate French translation, click on the white rectangle at the bottom right. English subtitles should then appear. Then click on the nut to the right of the rectangle, then click on “Subtitles” and finally “Auto-translate”. Select “French”. © NASA's Goddard Space Flight Center
To move forward, we might need to better understand the nature of the acceleration of expansion, and perhaps bring new physics to it. Technically, we would need to understand the physics behind Einstein's famous cosmological constant, which is actually the object we are talking about when we talk about dark energy.
Some (such as astrophysicist Thomas Buchert) suggested and showed that Einstein's constant could occur naturally if the cosmos, even if observed on a sufficiently large scale beyond a few hundred million light-years, would still not be considered homogeneous and isotropic Liquid could be considered galaxies, contrary to what we think we know. However, the general opinion of the scientific community is that we cannot reproduce the magnitude of the observed acceleration in this way.
Remarkably, a recent article published in the Monthly Notices of the Royal Astronomical Society (MNRAS), a version of which is freely accessible on arXiv, raises the idea that our universe is less homogeneous than we think. Although it is still not a matter of fully explaining the acceleration of its expansion, we postulate that our galaxy is located almost at the center of a zone of lower matter density in the Universe (a kind of vacuum bubble as we know them, intertwined with each other). through filaments of galaxies and galaxy clusters) it is possible to eliminate the famous Hubble tension and bring all observations into harmony.
Well, almost, because the researchers are also bringing the moon theory into play, the alternative to the dark matter theory, which postulates the existence of as yet unobserved particles on Earth or in space in detectors. Moon modifies Newton's laws of celestial mechanics, including the theory of gravity and the law of particle mechanics.
A cosmic bubble that is incompatible with the standard cosmological model?
The article proposing this solution to the Hubble voltage puzzle may leave you wondering. The team behind him includes the names of two researchers known for their work in support of the moon theory, proposed by Israeli physicist Mordehai Milgrom in the early 1980s.
There is Pavel Kroupa from the Helmholtz Institute for Radiophysics and Nuclear Physics at the University of Bonn in Germany, but above all Indranil Banik from St. Andrews University (United Kingdom). However, the latter is one of the co-authors of a recently published, breakthrough article in which he reports a refutation of the moon theory using astrometric data from ESA's Gaia mission to observe binary stars in the Milky Way. Futura will return soon in another article on this topic.
In the press release from the University of Bonn, Pavel Kroupa explains that the subdensity bubble that he and his colleagues postulate (there is evidence of its actual existence with the so-called KBC Void or Local Hole – named after astronomers Ryan Keenan and Amy Barger). and Lennox Cowie, who studied it in 2013, and it turned out that the Milky Way is not very far from its center) and whose contents are attracted by the more densely distributed matter around this bubble, has a size and properties that do not seem compatible with the standard model. What seems certain is that if we replace Newtonian gravity with Milgromian gravity, which accelerates the formation of galactic structures, we can produce it naturally in cosmological simulations.
To get a reasonably accurate French translation, click on the white rectangle at the bottom right. English subtitles should then appear. Then click on the nut to the right of the rectangle, then click on “Subtitles” and finally “Auto-translate”. Select “French”. © Cosmology Talks
In fact, years ago, Indranil Banik, Moritz Haslbauer and Pavel Kroupa had already proposed some of the ideas discussed today within the framework of a cosmological model based on the Moon, but also on a small component of hot dark matter in the form of what we call sterile neutrinos and the generated It is possible to solve several problems of the standard cosmological model, such as the existence of the KBC vacuum and the Hubble tension, as we can see in the video above.