What is the ‘theory of everything’?

What is the ‘theory of everything’? How to make the dream of establishing a single grouping theory of all the laws of nature come true? And, although the universe is one, it seems to resist the human mind to explain it in a unified way.

To date, it is known that there are four fundamental forces: electromagnetism, weak nuclear interaction, strong nuclear interaction, and gravity. It has been possible to merge the first with the second; however, the other two have been left as loose ends.

In this sense, modern physics is like a set of four strands that, to date, have not been able to interweave to form the long-awaited mat of the theory of everything or also known as unified field theory.

In this regard, Tec Review interviewed three Mexican physicists, who agree that finding a single theory of natural phenomena is a laudable aspiration and responsible for the way in which physics has developed throughout history.

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What is the ‘theory of everything’? In search of the unification of the laws

“The theory of everything is an aspiration of the reflective human being, the philosopher, and also the physicist when he tries to understand the universe”, he says Manuel Torres Labansat, researcher at the Institute of Physics, of the National Autonomous University of Mexico (UNAM).

This is observed, for example, in the seventeenth century, when Isaac Newton, a British physicist, had the spark of unifying the explanation of terrestrial and celestial phenomena under the same law.

Before him, the Aristotelian idea still prevailed that the laws of the Earth referred to imperfect phenomena and had nothing to do with the incorruptibility of the movements of the celestial vault, where the stars were believed to be fixed like tacks.

“The emergence of classical mechanics implied that the description of phenomena on Earth and in the stars were described with the same laws: those of universal gravitation. Newton realized that they are the same and precisely the fall of an apple to the ground is given by the same law that makes the Moon rotate around the Earth. That was a fantastic unifying principle ”, comments this scientist from UNAM.

This theoretical marvel was also perceived by Paul Valéry (1871-1945), a French poet, who summarized the same idea as Torres Labansat in the following sentence:

“One had to be Newton to realize that the Moon is falling, when everyone sees that it is not falling.”

The second step was taken in the direction of the unification of two apparently alien phenomena, electricity and magnetism, but which in the middle of the 19th century, James Clerk Maxwell, a British physicist, merged into electromagnetic theory.

“He also realized that this theory predicted the existence of electromagnetic waves, and when he calculated the speed with which these waves propagate, he was surprised that they do so at the same speed of light. Thus, he concluded that light is also an electromagnetic phenomenon ”, explains Torres.

So, in this way, Maxwell managed to unite not only two phenomena previously considered as alien, electricity and magnetism, but three, when he saw that light was also part of his theory.

“And this had tremendous implications, not only in understanding nature, but also in applications. For example, the possibility of transmitting signals (such as television or radio) is based on the theory of electromagnetic waves ”, Torres details.

The third great leap in physics on the path of unification was the famous formula of energy equals mass times speed of light squared, formulated by Albert Einstein, a naturalized American German genius, considered the most brilliant physicist of the 20th century.

“With this formula it is understood that in some way the mass is exchanged with the energy, so this means that they are closely related. It is another fantastic unifying principle ”, assures this researcher from UNAM.

The train’s march has stopped

This journey of scientific refinement towards a completely unifying theory has had its discontinuities and is currently on pause like a train in a station waiting to see the green traffic light again, and this may never happen for structural reasons of physics. that stop that tendency of the human being to construct totalizing theories in the field of natural science.

This presumed impossibility is explained by Shahen Hacyan, who is a researcher at the Institute of Physics of the UNAM and considered the best popularizer of physics in Mexico.

“There cannot be a theory of everything, for a very simple reason: physics has several levels. So, for example, an engineer to build a bridge or a building needs Newtonian physics, but does not require quantum mechanics or relativity, while a physicist interested in how atoms or molecules behave uses quantum mechanics , but you don’t need Newtonian physics. In the same way, an astronomer who wants to study very violent phenomena in the universe needs the theory of general relativity, but quantum mechanics and Newton’s theory are not useful ”.

However, Hacyan says that physicists who specialize in studying the constitutive particles of atoms – protons, neutrons and electrons – would like to find a unifying theory, but so far there is no evidence that this is possible.

“A big problem for them is having a quantum theory of gravitation, and there were several attempts at this through superstring theory that was in vogue in the 80s and 90s, of the last century, but it did not lead to anything. ”, He specifies.

In scientists there is a desire, perhaps a deep metaphysical yearning, to find a single theory with very few postulates that explains everything.

“But who knows if that exists. And if it exists, maybe nothing else is like the title of a movie ”, says this scientist, laughing.

Gravity, “the bogeyman of physics”

Recapitulating, the scientists managed to realize that electricity and magnetism are the same phenomenon: electromagnetism; later, according to Hacyan, they managed to link this explanation with one of the four fundamental forces of nature, the weak nuclear force, which explains processes of atomic decay. So, as a result, in the 20th century the theory of electroweak interactions emerged, and there the train of physics stopped.

“It has no longer been possible to integrate this well with the strong nuclear interactions (which explain the reason for the union between protons and neutrons). Yes, there is a separate theory that describes strong interactions well, but its equations are extremely complicated, ”he says.

And then it would be necessary to unify the force of gravity, and that is the “great bogeyman of physics”, according to this scientist from UNAM. There have been research groups around the world that have tried their best to achieve this, but have not succeeded.

Then Tec Review poses the question expected by those who hope that science will one day offer a comprehensive description of the universe.

When do you think a theory of unification of all forces in nature will be formulated? Hacyan’s response is as follows:

“My opinion is that it cannot be done. I think that gravity cannot be quantized for very deep reasons, but, well, not all scientists think that, so they keep looking for theories about it ”.

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One, two three … an infinity of universes

Myriam Mondragon Ceballos, a researcher at the UNAM Institute of Physics, agrees that achieving a theory of everything seems like an impossible mission, especially due to the inescapable hierarchy between the levels of interpretation of physics.

“The problem is that quantum theories of gravity are related to very small masses, while the theory of gravity is conceived for really large masses, so it is not known if they can be unified.”

Mondragón considers that physics will surely reach more fundamental theories that bring together a greater number of natural phenomena; however, he agrees with Hacyan in the sense that there are different regimes that, as physical systems become more complex, involve phenomena that necessarily have to be described with different theories.

To overcome this obstacle at the different levels of the interpretive ladder, some physicists affirm the existence of parallel universes and that we are only seeing one of those universes; then there would be other universes, each with its own laws.

“Then what would the whole be, the one that we live or the one of absolutely the entire infinite set of all the possibilities of universes? The answer leads to questions that are no longer the realm of physics, but of philosophy. For this reason, I believe that it is possible to describe only a part, but not the whole ”, says this scientist from UNAM.

In order not to fall into speculation that makes us take our feet off the ground, Mondragón recalls that finally physics is based not only on abstractions, but also on tangible evidence; if they are present, physics advances; if not, you cannot take the next step.

Platonic science

In this regard, Shahen Hacyan comments that highly theoretical physicists often confuse mathematics with the world that can only be measured objectively through clocks, balances, microscopes, among other laboratory devices.

“Mathematics is a very powerful tool to describe natural phenomena, but it also has its limitations. Regardless of this, many very theoretical physicists have the idea that with mathematical theories they will understand the whole world ”.

Hacyan, showing off his great talent as a popularizer of science, explains this situation by saying that mathematics is like making a map of a city, which may be very precise, but in the end it is not the city.

“I am a theoretical physicist, but I do not pretend that you reach the last, last, through mathematics, although I do like to apply mathematics to problems of quantum mechanical physics and relativity; mathematics is very powerful ”.

At this point in the conversation, one of humanity’s oldest dilemmas arises. Is mathematics a simple instrument of natural science or does it really have a life of its own, as Plato claimed?

“It is an old philosophical discussion if mathematics exists independently of human beings or not, well who knows, but for now it beats me that they are independent of human beings. It is the Platonic interpretation that there are other ideas in a parallel world, in the so-called world of ideas, and there would be mathematics ”.

These reflections are deep and touch the very foundations of science that, possibly, did not arise together with the human being, but was previously there, unified with poetry, in a complete and eternal world. For this reason, it was not by chance that another of Paul Valéry’s famous literary brushstrokes was that “poetry is the most exact of the sciences”.

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