The saga of the Phoenix  volume 3

 The theory, best known by the general public, on the origin of the universe is that of the Big Bang. The great explosion, which occurred, most likely 13.7 billion years ago, which generated the universe and which continues to expand it, perhaps to infinity or perhaps to a point from which it will then contract to return to its initial stage. The classic version of the Big Bang theory assumes that everything started from a point-like entity with no volume but with infinite density and energy. This concept was necessary to respect Einstein's General Relativity and other evidences, such as the red shift and the temperature of the cosmic background radiation, which have been experimentally ascertained.
Many scientists contest this theory as it would violate some well-known physical laws, such as the principle of energy conservation, but, above all, it would result in conflict with quantum mechanics.

Many other theories on the origin of the universe have been hypothesized based on mathematical models deriving from experimental observations, unfortunately incomplete. To decide whether the universe is in infinite expansion or, having reached a certain point, collapses to return to the starting point (universe oscillating between big bang and big crunch) it would be necessary to know exactly the density of matter present or its equivalent energy. Achieving an average density of at least three protons per cubic meter, defined as critical density, would allow the contraction phase and would define the oscillating universe. Recent measurements have established that the density is slightly lower than the critical one, so it could be deduced that the universe is open and non-oscillating.
On the other hand, the hypothesis, formulated by many scientists, of the presence of dark matter prevailing over observable matter, would lead back to the oscillating universe. Everything is enormously complicated with the introduction of new quantum gravity models that could avoid the use of dark matter to affirm the oscillating universe.
That the universe expands to infinity or that at some point it begins to contract until it returns to the starting point, for a human being present on Earth today, it would be irrelevant in both cases. On the other hand, what could have effects in times comparable to the duration of human life, is the phenomenon of entanglement.

Quantum mechanics has enormously revolutionized scientific thinking since the beginning of the twentieth century. Its shocking principles, such as, for example, the uncertainty principle, according to which a particle can be identified but not exactly where it is at the moment of detection. This also changed the representation of the structure of the atom. The old Bohr model, with the central nucleus surrounded by electron orbits, no longer corresponds to reality. The electrons are distributed on probabilistic surfaces that surround the nucleus, since it is not possible to predict which of the possible orbits the single electron will travel.

The even more disconcerting aspect of quantum mechanics is the discovery of instantaneous reactions between particles separated even by long distances. In simple terms, two particles belonging to the same "mother" particle, once separated, remain connected in some way and interact even over a long distance. By acting on one, the effect is also found on the other. The nature of this link is still unknown and, what happens, contrasts with Einstein's Theory of Relativity, but it is experimentally ascertained that it does. Physicists come to speculate that the same can happen on a macroscopic scale. This link, or interaction if you prefer, would travel at a speed greater than that of light, which would upset all current theories of classical physics, which consider the speed of light to be an insurmountable limit. Not only that, but it would radically change all perspectives regarding the impossibility of reaching distant stars or of coming into contact with other beings.

A trip to Mars, when it is very close to the Earth, that is about 55 million kilometers, would last just under a year with a good traditional rocket, while an electromagnetic wave would take a few minutes. It would not make sense to imagine, even assuming we can travel at the speed of light, the duration of a hypothetical trip to a star whose light reaches us today but started 30 billion years ago, as in the case of the red dwarf galaxy classified as z8_GND_5296 which it is located at such a distance and that it seems to be one of the most distant objects from the Earth, until now discovered. But it is not certain that other even more distant ones do not exist, indeed, very approximate estimates by astrophysicists, tell us that the diameter of the observable universe is of the order of 93 billion light years. This, only for the potentially observable part, not all. By comparison, our galaxy is a microbe of 100,000 light-years in diameter. These seem to be the limits within which humanity is constrained. Provided that entanglement, this strange quantum phenomenon, does not open up new horizons for us, unthinkable at the moment.