Probably other people had formulated these questions before him, but Leibniz has bequeathed us an extraordinarily valuable collection of documents that collect his reflections, and without which perhaps we could not fully interpret the essential contributions he made in mathematics, physics, logic, metaphysics, geology or philosophy, among other disciplines.
Observations suggest that the universe arose from a vacuum, but not from one like that described by our classical conception of a vacuum, but from a false vacuum.
Leibniz is, and I am not exaggerating in the least, one of those giants on whose shoulders current scientific knowledge stands. Unfortunately, he died without even being able to touch the answer to one of the questions that, according to his writings, most concerned him with the tips of his fingers. Why is there something instead of nothing? What is the real cause of existence?
Fortunately, his reflections and the knowledge he has transmitted to us have inspired many researchers who, using the scientific development that 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 it is possible that the universe that we know has arisen from a vacuum, which is what our observations seem to reflect. But not just any void. Of the true vacuum: the quantum vacuum.
From the classical idea of the vacuum to the quantum vacuum
One way to define the vacuum 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 classic conception of the 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However, this view has been superseded by modern science.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 have been verified experimentally, are very profound. And also very surprising.
From the perspective of quantum mechanics the vacuum is not empty; 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 come and go very quickly. These are what are known as vacuum fluctuations, and the best tool we have to understand them is Heisenberg’s uncertainty 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 at the atomic scale, there is no we can simultaneously determine the value of all the 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.
The uncertainty principle states that there are some pairs of magnitudes, such as the position and momentum of a particle, that are not simultaneously defined. This means that the harder we try to measure its position, the less information we have about its linear momentum, which is defined by its mass and its speed at a given instant.
And the same thing happens in reverse: the greater the precision with which we measure the amount of movement of a particle, the more uncertainty we will have when determining its position at a given instant. Heisenberg’s uncertainty principle is a very valuable tool that helps us understand vacuum fluctuations because it establishes an uncertain relationship between the value of the energy of a system and the time we spend 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 it manifests itself in the form of a field. Furthermore, a field cannot have fixed energy at any instant, 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 arose from a vacuum. From the quantum vacuum full of fluctuations that we have 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 be done, 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 cosmic inflation theory is the idea that the universe started from a vacuum state of a field that scientists call an inflaton. At that primeval moment, this was the only field that existed, and it presumably extended throughout space, which is assumed to be infinite in extent. One property of the inflaton is that it could persist in a false vacuum state in which it had no particles associated with the field, but without remaining in its lowest energy state.
The curious thing is that by introducing gravity in this scenario from a theoretical point of view, 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 differed from it in that it could adopt a false vacuum state in which its energy was not the minimum possible.
Initially, the inflaton must have been in this state of false vacuum, but with a marked tendency to reach a state of true vacuum. 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 prompt 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 leads 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 the 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 we intend 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 certainly a complicated topic, but it’s also an exciting one and we’d love to dive into it with you.