This article gives idea behind the quantum origin of the universe. The germ of this article we owe in a way to the German mathematician, philosopher and logician Gottfried Leibniz. The limited but very meritorious degree of development of scientific knowledge in the seventeenth century did not prevent him from wondering about the true origin of the universe . About the nature of matter. About the cause of existence itself.
Probably other people had asked these questions before him, but Leibniz has left us an extraordinarily valuable collection of documents that collect his reflections, and without which we might not be able to fully interpret the essential contributions that he made in mathematics, physics, logic, metaphysics, geology or philosophy, among other disciplines.
Leibniz is, and I am not exaggerating in the least, one of those giants on whose shoulders current scientific knowledge stands. Unfortunately, he passed away without even being able to touch with the tips of his fingers the answer to one of the questions that, according to his writings, most disturbed him. Why is there something instead of nothing . What is the true cause of existence.
Fortunately, his reflections and the knowledge he has transmitted to us have inspired many researchers who, using the scientific development we have achieved during the 20th century and the first two decades of the 21st, have managed to formulate hypotheses that seek to explain the nature of matter. . How is it possible that the universe we know emerged from a vacuum, which is what our observations seem to reflect. But not from any void. From the real vacuum: the quantum vacuum.
From the classical idea of the vacuum to the quantum vacuum
One way to define emptiness that is easy to get comfortable with is to describe it as a region of space in which there is an absolute absence of matter and energy. This is the classical conception of vacuum, and it invites us to accept that there can be, and indeed do exist, different degrees of vacuum that can be identified by comparing the pressure in the region of space that we want to measure with atmospheric pressure.
However, this view has been superseded by modern science. The development of relativistic mechanics and quantum mechanics has allowed scientists to elaborate a description of the vacuum much more adjusted to reality in which it is conceived as a physical state of a system that is linked to the minimum energy that it can have. The implications of this idea, which has been tested experimentally, are very profound. And also very surprising.
From the perspective of quantum mechanics the vacuum is not empty; it contains waves that originate randomly. Also, these waves behave like particles, so one way to define this quantum vacuum is to describe it as a soup of particles that arise and are destroyed very quickly. This is what is known as vacuum fluctuations, and the best tool we have to understand them is the Heisenberg indeterminacy principle.
We do not need to know what this principle tells us in its entirety, but to move forward it is good for us to know that it is a theorem that defends that in the physical systems described by quantum mechanics, which studies the properties of nature on an atomic scale, we do not we can simultaneously determine the value of all physical parameters that we can observe. In classical mechanics we can describe any physical system by listing the value of the parameters that we can measure, but in quantum mechanics we cannot.
In fact, the principle of indeterminacy states that there are some pairs of quantities, such as the position and moment of a particle, that are not defined simultaneously. This means that the more we try to measure its position, the less information we will have about its linear momentum, which is defined by its mass and its velocity at a given instant.
And the same thing happens in reverse: the greater the precision with which we measure the momentum of a particle, the more uncertainty we will have when determining its position at a given moment. Heisenberg’s indeterminacy principle is a very valuable tool that helps us understand vacuum fluctuations because it establishes an indeterminacy relationship between the value of the energy of a system and the time we spend in measuring it.
The immediate consequence of this relationship is that if, as we have seen, the vacuum is not empty, but contains waves that behave like particles, it also contains energy, and manifests itself in the form of a field. Furthermore, a field cannot have a fixed energy at any moment, which implies that in a vacuum the energy of the fields cannot be constant. It fluctuates continuously. This is the starting point for the next section of the article.
The theory of cosmic inflation and the origin of the universe
The measurements that scientists have obtained experimentally suggest that the universe emerged from a vacuum. From the fluctuating quantum vacuum we just described. We still do not have a theory that categorically explains the origin of the universe, but the most accepted because it has observational support, which has not prevented it from also having detractors, is cosmic inflation.
There is still much to do, and there are still many phenomena that we cannot explain, but scientists trust that technological development will allow us to obtain more precise measurements that can be used in the future to correct and further develop current theories, or to make new ones.
The germ of the theory of cosmic inflation is the idea that the universe started from a vacuum state of a field that scientists call an inflaton. At that primordial moment this was the only field that existed, and presumably it extended throughout all space, which is assumed to be infinite. One property of the inflaton is that it could persist in a false vacuum state in which it lacked particles associated with the field, but without remaining in its state of minimum energy.
The curious thing is that by introducing gravity from a theoretical point of view in this scenario, the inflaton acquires an enormous gravitational repulsion responsible for the expansion of space itself. This is what is known as inflation. Theoretical physicists who defend this theory believe that the inflaton had an energy profile similar to that of the Higgs field, but it differed from this in that it could adopt a state of false vacuum in which its energy was not the minimum possible.
In fact, initially the inflaton must have been in this false vacuum state, but with a marked tendency to reach a real vacuum state. During its fall to this last state, it must have been subjected to a repulsive gravity, which, as we have seen, would cause the expansion of the space in which this field was located. Upon reaching the minimum energy value, the inflaton could be subjected to fluctuations that would incite it to increase its energy level and dissipate its initial energy.
If, as we have just seen, the field tended to reach a true vacuum state from a false vacuum state in which its energy was higher, the only possible strategy was to release its initial energy. And this brings us to the culminating idea of this theory: quantum mechanics defends that the release of energy is carried out by generating fields and their associated particles, so that physicists who defend the theory of cosmic inflation believe that this was the mechanism that led to the creation of the fields and particles that make up the universe in which we live.
In this article we have only scratched the surface because our intention is to make it as affordable as possible, but if you liked it and want us to continue investigating the origin of the universe in other reports, let us know in the comments. It’s definitely a complicated subject, but it’s also exciting and we’d love to dive into it with you.