In the beautiful setting of Villa Mondragone, during the second interdisciplinary Global Symposium, we had the occasion to interview Mr. Guido Corbò, a former lecturer of General Physics in Rome University “Sapienza” and theoretical physicist working in field theory and high energy physics, particularly known for his contribution in quantum chromodynamics.
Guido-CorbòThe word “boundaries” was the core and the base of the first section of the meeting. Four professionals coming from all different backgrounds gave a speech addressing the theme from their own perspective. Then a second phase began, where the guests interacted with each other to reach a common and eventually interdisciplinary vision:  not the sum of each but a mixture of all.

Eventually, rather simply, a meeting point between the speakers was reached, and the frictions and contraposing points of view enriched the discussion.
Particularly, a theme that raised many discordances emerged: the infinity, analyzed both mathematically and philosophically. It seemed that to address the theme of boundaries it was necessary to reflect on its opposite.
Professor Corbò in his speech focused on the meaning and importance of boundaries within physics. Right after the conclusion of the Symposium’s first section, we found a kind man, available to talk about physics with the accuracy and competence of a Professor and the pleasure of a friendly talk, and together we went deeper into some of the themes he addressed during the lecture.
“Since the theme of the symposium was “boundaries” – he said – I tried to include this word in my speech and actually I put the word at the very base of my entire discourse. I tried indeed to define, as much as clear I could, where and what are “boundaries” in physics”.

What comes to a physician mind when the word boundaries is pronounced?

The word “boundaries” frequently recurs in our daily life. In a philosophical meaning, it could be understood as a limit to our knowledge. When you say to me “boundaries”, I could admit I have limits, I know things until a certain point. It could be understood as the narrowness of the knowledge that pushes and encourages to widen the horizon. After having spent a lifetime in studying this subject, I still keep going deeper in these things trying to better understand them, because, in the end, there is no real boundary. In physics, when one start thinking he understood everything, he should retire.
However, from a more technical point of view, hearing the word boundaries, it comes to my mind differential equations and event horizons of a black hole.

The topic of black holes fascinates most people, also those that are not experts in physics. Could you better explain it?

Yes, it is really a theme that turns on everyone’s imagination. I will try to be clear and to go straight to the point. In proximity to a celestial body, there is a gravitational field, as on Heart, that is more intense as greater the mass and smaller the volume of the celestial body is.
A black hole is a celestial body that potentially could have mass billions of times bigger than the sun, and this, to keep sticking to the original topic, for sure goes well beyond our imagination’s boundaries. Moreover, this enormous black hole’s mass is concentrated in a minimal area that is impossible to quantify since a celestial body of this kind is not visible because of the gravity’s boundary. To better understand it, if you throw a stone up in the air it will eventually fall back down, however, if you throw that stone with the speed of 40000 km per hour, or 11 km per second, it will escape gravity. Therefore not even the light escape black hole’ gravity and if we do not receive lights making it impossible to be observed. The light, the vision is our mean of communication and a black hole is an astronomical object from which never comes lights,  a boundary to our communicative ability. You can observe a black hole when you notice astronomical objects that rotate around nothing, as the planets orbit around the sun, you understand that inside that orbit there must be something, the black hole indeed.
However if you are far from the black hole nothing occurs, as if you were on a dinghy on the Niagara river going towards the falls, you could row against the current until a certain point where you can’t resist anymore. In the same way if you move towards a black hole, passing the boundary of the event horizon you do not even notice anything, however you will not be able to go back and will keep falling in the black hole.

Boundaries are, therefore, a concept that recurs frequently in physics from different perspectives…

Yes, that is true. The only instruments through which is possible the study of physics is mathematics, there is no other way to describe the reality that surrounds us.
In mathematics the concept of “infinity” has nothing of dramatic (referring to some debate on that word he had during the symposium with the other guests), yes it is important and profound but from a mathematical point of view is basic. Just think about the asymptote, a line that a curve approaches, as it heads towards infinity. Physics is an experimental science, it has to explain what happens. An apple falls from the tree? physics simply describes through laws we studied at the high school how this occurred. There is nothing more, that’s why I say physics is a modest science, meaning that it does not aim to explain the sense of the universe and its creation, only to describe what happens, how the universe works.

The other speakers talked about boundaries as something that has to be overcome, as an obstacle. You, as a physician, spoke of them as a necessary tool in order to study the laws of nature, placing limits to better understand its infinite dimension.

“If you look at the universe, is not possible to see boundaries, it seems to be infinite. Rooms, for instance, instead have boundaries and could be labs for the quantum mechanical experiment. Indeed, in order to study a phenomenon and describe it mathematically, it has to be carried out in a confined environment.
Hence, boundaries must be set out in order to solve problems, and, once solved, the “artificial” boundaries are removed or better led to infinity, where the solution approaches asymptotically to a situation to be verified experimentally.
Often, to solve problems in physics there is the need of placing them into imagined boundaries to remove them later.  Analyze, for instance, the Archimedes principle.
If you place a physical body in the sea, it floats. How it floats depends on the boost from bottom-up equal to the weight of the water’s volume that it moves.
This law of nature can be confirmed only thanks to the boundaries.
A ship floats either in the Mediterranean Sea and in the Atlantic ocean, in the same way a ball does it into a bathtub or also in the sea as well. However, if you put the ball into a Small bowl, setting, therefore, defined boundaries, the Archimedes principle is easily verifiable looking at how much the water raises once the ball is placed in the bowl.
It is important to divide the physical reality from philosophical conjectures, for these two different perspectives you have two different meanings of boundaries and infinity.


Giorgio Severi and Rebecca Biraschi.

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