All physical systems in the observable Universe, whether objects or living beings, are made of baryonic matter, i.e. particles from the Standard Model, such as electrons and quarks. However, as early as the 1930s, the hypothesis of another type of matter beyond the Standard Model was proposed:dark matter. This hypothetical matter, allowing among other things to explain the rotation curve of galaxies and the formation of large structures, is now included in the standard cosmological model. What would happen if, instead of baryonic matter, we were made of dark matter?
In 1933, while studying the dispersion of the velocities of seven galaxies located in the Chevelure de Berenice cluster, the Swiss astronomer Fritz Zwicky noticed that these velocities were too high compared to theoretical predictions. The dynamic mass of the cluster is indeed 400 times higher than the luminous mass (visible mass). In the 1970s, American astrophysicist Vera Rubin discovered anomalies in the rotation curve of spiral galaxies. The hypothesis of an invisible but gravitationally influential matter then appeared.
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A supercomputer has just weighed the weight of the ideal candidate to compose dark matter
In the following years, the dark matter hypothesis will be reinforced until it is integrated into the standard cosmological model:the Λ-CDM model (for cold dark matter , cold dark matter).
In this model, dark matter forms a cosmic web between galaxies and clusters of galaxies and has contributed, through its gravitational influence, to the formation of large structures. Although still hypothetical, several observational clues now tend to confirm its existence.
The human being is made up of approximately 7×10 27 atoms, all bonded to each other. The baryonic matter that composes us is found mainly in the form of atoms.
Atoms consist of an atomic nucleus around which electrons move; more precisely, these electrons move within atomic orbitals which are position probability densities, provided by the Schrödinger equation. According to quantum electrodynamics, i.e. the quantum theory of electromagnetism, electrons (negatively charged) interact with the nucleus (positively charged) via photons.
The atomic nucleus is made up of hadrons, more specifically baryons (composite particles made up of three quarks), and more specifically nucleons (protons and neutrons).
These nucleons are composed of three quarks up and down whose distribution differs depending on whether it is a proton (2 quarks up + 1 down quark ) or a neutron (2 quarks down + 1 quark up ). According to quantum chromodynamics, i.e. the quantum theory of strong nuclear interaction, these quarks are bound by gluons (bosons of zero mass).
It is also the electromagnetic interaction that ensures the cohesion of matter at the atomic scale. Indeed, atoms form molecules by establishing mainly electronic chemical bonds (covalent bonds) in which they share electrons within molecular orbitals. It is this cohesion that, for example, prevents you from crossing walls. While Earth's gravity keeps us on the surface.
Unlike baryonic matter subject to the four fundamental interactions, dark matter is subject only to gravity. Indeed, until now, theoretical models describe dark matter as insensitive to electromagnetic interactions, strong and weak. Or having a cross section (probability of interaction) so negligible concerning the bosons of these interactions that it is undetectable. Furthermore, dark matter does not appear to interact with itself or collide with other particles.
What would happen, then, if all the baryonic matter in the Universe was converted into dark matter? Since dark matter is insensitive to the strong force, the subatomic scale structure would completely dissociate because the binding force (the gluons), which previously held the quarks together, would immediately disappear.
Similarly, at the atomic scale, the electromagnetic interaction would no longer apply, the cohesion of atoms and molecules would therefore also suddenly vanish, and no more light would be emitted. Clearly, any object and living being would disappear in a fraction of a second, completely disintegrated and invisible.
With an average speed of about 3000 m/s due to the thermal movement of each particle (protons and neutrons), all of the dark matter constituting objects and living beings would be propelled in all directions. However, since this velocity is lower than Earth's escape velocity, these dark matter particles would remain gravitationally bound to the planet. Then the latter would eventually follow an elliptical orbit with the center of the Earth as its focus. With no electromagnetic interaction to prevent dark matter from traversing the planet, it completes a complete revolution in 88 minutes.
Since, except gravity, no other force affects the dark matter particles, the latter do not lose any energy while crossing the Earth, and would therefore traverse their orbit indefinitely.
In addition, the gravitational influence of the Sun and the Moon lead very slowly to the lengthening of the duration of the terrestrial days. A slightly longer day means that everything on the Earth's surface, from the ground to the oceans to the atmosphere, takes longer to return to its starting point each turn. But not dark matter.
Instead, dark matter will slowly drift in time away from its original location as Earth slows down. Dark matter is only affected by gravity. Even if the rotation of the Earth changes, dark matter is not affected. After a year, the initial position of the dark matter particles will be shifted by 50 cm; and this lag increases with time. After about ten years, the shift from the initial position will have reached 500 m.
Eventually, all dark matter particles will remain gravitationally bound to the Earth, tirelessly traveling in an elliptical orbit passing through the planet as if it were only a vacuum. Without the dissipative effect of the other three fundamental interactions, the initial energy and momentum of matter particles are, in fact, perfectly conserved.
