December 7, 2022

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Science & Books / The Dark Universe

When I encounter a popular scientific text, I always have the question: what goal did he set for himself and whether he achieved it. In fact, the risk of a publication business is to provide information only without reasonable justification, which may require specific knowledge.

In the case of this work, the author states that he “intends to present the mysteries of the universe with an attempt.” to explain (and not just telling us) what we understood and what remains shrouded in the most complete mystery.”

This attempt has already received significant recognition: the first edition (1917) of this text was awarded the “Giancarlo Dosi” national prize for scientific publication, and therefore its course is worthy of study.

In the beginning, one of the chapters illustrates the observing panorama of the universe, from the solar system to our galaxy and the enormity of galaxies that make up the universe. It is a simple description of the results of scientific observations, without formulas, a characteristic that runs throughout the book, emphasizing its popular side.

Later there will be more accurate indicators that will justify the statements made: in this sense there is progress.

To clarify the inevitable limitation of a description that does not go into the details of physical laws, see one of the statements made about astrophysical observations: We see past in time because the farther away galaxies are, the longer it takes for light to reach us. But how do we measure the distance to galaxies? The text doesn’t say that, and in fact it takes an entire chapter of a physics book to fully answer this question.

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In the next chapter we present one of the topics that will then be among the most advanced: that of dark matter, and the study of evidence for its existence: here the accuracy in explaining scientific results allows the first understanding even in the absence of formulas.

Two chapters dealing with aspects of physics related to the structure of the universe follow.

The first deals with the intimate formation of matter, up to the final division (hadrons, leptons) and a brief description of the four fundamental forces, gravitational force, electromagnetic force, strong nuclear force, and weak nuclear force.

The second is devoted to evidence and phenomena related to general relativity, in particular black holes and gravitational waves.

We then move on to the main topic of the entire text: the nature of dark matter, which is perhaps the most relevant and also interesting because of the breadth of the discussion.

Two chapters are devoted to it. Initially, various hypotheses were investigated in which dark matter consists of ordinary matter, in various forms, for example black holes of primordial origin. In Chapter Two, we examine the hypotheses of a new type of particle, different from ordinary matter, and capable of interacting only through the force of gravity. In fact, none of the hypotheses presented in the two chapters has at present found empirical verification; For her sake some researchers have formulated an alternative hypothesis for the existence of dark matter: modulating the gravitational force over large distances, which would decrease less than expected in a way that is inversely proportional to the distance rather than its square.

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The last part is dedicated to the Big Bang model. We start from the Hubble-Lemaître law, which regulates the expansion of the universe and allows us to determine its age. Subsequently, the stages of its expansion, the presence of background radiation, CMB (Backgroomd Cosmic Microwave), which provides a picture of the universe about 300,000 years after the Big Bang. The function of dark matter in the formation of galaxies is also discussed. In the last chapter we talk about the fate of the universe: depending on the density of the existing matter, the universe must expand forever (Ω <1) أو ينهار (Ω> 1). The empirical evidence is that exactly Ω = 1. However, the sum of visible matter and dark matter provides only 30% of the matter necessary to be Ω = 1. Moreover, at the end of the last century, a new phenomenon was discovered: the expansion of the universe from a certain moment onwards in acceleration; According to current theories, this is due to the presence of dark energy that causes repulsion: if this effect was permanent, then the end of the universe would be a cold, cold darkness. For dark energy, according to the Einsteinian formula E = mc2And the 70% of the mass of the universe is related to each other, which makes it possible to arrive at the value Ω = 1.

The author concludes by talking about a “dark conclusion” because the mystery of the universe remains somewhat intact, even if he reconfirms confidence that the research can shed light on a future that is lacking today.

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One last note. It is not possible to address all aspects of science in one common work: in this work that is so precise from a descriptive point of view, there is no historical dimension found in other texts on the vision of the universe.

Andrea Simati

dark universe

A journey through the greatest mysteries of the universe

Karruce Editor, Rome 2021

Pages 204 € 17.00

Lorenzo Mazzoni review

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