The Nature of Time: an open question between Physics and Philosophy

Tuesday 12 Dec 2023, 15:00 → 19:00 Europe/Rome

Aula Fermi (Enrico Fermi Study and Research Center)

Ilia Musco (Istituto Nazionale di Fisica Nucleare, Rome), Paolo Pani (Istituto Nazionale di Fisica Nucleare), Alfredo Leonardo Urbano (Istituto Nazionale di Fisica Nucleare)

Within the program of the workshop Future Perspectives on Primordial Black Holes, that will gather in Rome experts in gravity, early Universe cosmology and black holes, INFN and Spaienza University organize a special event at the Enrico Fermi Study and Research Center (CREF), dedicated to one of the oldest and profound questions in human history:

What is Time?

The passage of time is probably one of the most straightforward aspects of human perception, that has always been associated with the passing of seasons and cycles of celestial objects, used to measure the flow of life. 

Yet, the concept of time has been investigated and questioned by philosophers since the anciet times, and later on also by scientists, throughout the whole history of human thought. 

Does time flow or simply is? 

What is the orgin of the arrow of time?

From the absolute concept of time proposed by Isaac Newton, to the relativitic one formulated by Albert Eisntein, and the more recent attempts of quantum gravity to reach an unifed theory between the theory of general relativity and quantum mechanics, modern physics has not found yet a definitive answer to explain which is the true nature of time.

With the help of experts in theoretical physics and philosophy, we will open a debate about one of the most fascinating and difficult questions in the human quest for the meaning of reality.

We have reached the maximum number of participants that we can accomodate in the room. For all the other people interested the event will be streamed on Zoom.

Zoom Link:  https://us06web.zoom.us/j/84253976940?pwd=b5Y8jNkYGYOi0Gx4LqtADGOCrvGvxM.1

Meeting ID: 842 5397 6940 
Passcode: 518457

List of topics:

• Mach Principle and space time structure
• Time in the history of science and philosophy
• Time and atemporality in current philosophy
• The Arrow of Time
• Time in physics: theroy and models
• Time in quantum gravity and quantum cosmology  
   

List of invited speakers:

Julian Barbour (University of Oxford, UK)                            
Silvia De Bianchi (University of Milan, IT)                             
Stefano Liberati (SISSA Trieste, IT)                                                     
Luciano Pietronero (CREF Rome, IT)             

Moderator: Roberto Capuzzo Dolcetta (Sapienza University of Rome, IT)                 
 

Scientific Secretariat: Anna Lo Piano                            
Organizing Committee: Ilia Musco, Paolo Pani, Alfredo Urbano

Support: This event is supported by INFN Fellini Fellowship DarkPBH "Dark Matter and Gravitational Waves" (H2020-MSCA-COFUND-2016 G.A. n. 754496) and by the ERC project DarkGRA “​Unveiling the dark universe with gravitational waves” (ERC-2017-StG 757480).

 

                         

 

15:00 → 15:30 Registration and Welcome Introduction

15:30 → 17:30 Plenary Invited Talks

Convener: Dr Ilia Musco (Istituto Nazionale di Fisica Nucleare, Rome)

15:30 Mach Principle and the nature of Inertia

The gravitational mass is a local property of particles like the electric charge, while the inertial mass is the resistance to acceleration, quite a different property. Mach’s principle states that inertial forces should be due to the interaction of a body with all the other masses in the universe. In General Relativity this principle is not fully present and is replaced by the equivalence principle, according to which inertial and gravitational masses are linked by the gravitational constant, which is a fixed number. However, according to a strict interpretation of Mach’s principle, the inertial mass should be non local and depend on all the other masses of the universe and their positions. In this perspective the gravitational constant cannot be just a fixed number. In 1918 Thirring studied the metric inside a rotating spherical mass shell and it was clearly inspired by the conceptual problem of Mach’s principle. This study revealed the appearance of a force with the structure of Coriolis force. No centrifugal like force was present but there was also a curious vertical force. In 1973 we considered a cylindrical rotational symmetry and extended the approach to second order in the gravitational constant. We found that a rotating cylinder leads to a metric which gives exactly the Coriolis term and the centrifugal one with the correct relations. Recently we have reconsidered this problem extending to the case of a linear acceleration. All these results strongly point to the idea that real inertia is the outcome of a relative motion and this would require a generalization of GR theory.

Speaker: Luciano Pietronero (CREF, Sapienza University)

16:00 From the past to the future of time

Time has been a constant puzzle for mankind and the development of modern science just served to even more pinpoint the tantalising nature of this concept and its apparent clash with the current physical understanding of the world. In this brief seminar I will try to convey a brief history of time and try to point out foreseeable developments of our understanding of its nature within the fabric of reality.

Speaker: Stefano Liberati (SISSA, Istituto Nazionale di Fisica Nucleare)

16:30 Shapes and a Dynamical Arrow of Time

I will show that if the philosophically dubious absolute elements which Newton introduced when he created dynamics are eliminated, his theory of gravity applied to a model universe leads to a theory of time and its arrow that is a direct consequence of Newton's laws. The arrow, which does not arise from a special condition of low entropy in the early universe that must be imposed in addition to the dynamical laws, points in the direction of increasing order and not, as widely believed on the basis of the second law of thermodynamics, entropic disorder. I will also draw attention to the dramatic change of perspective that results from the recognition that no ruler exists outside the universe to measure its size. Only the shape of the universe is physically meaningful. Since from the point of view of group theory Newton's and Einstein's theories of gravity have the same architectonic structure, these Newtonian features may well be true of our universe described by Einstein's theory.

Speaker: Julian Barbour (University of Oxford)

17:00 Paradoxes and metaphors of time in between physics and philosophy

In this contribution I describe the fundamental tension that characterized Western culture in representing time as being fundamental and emergent, especially in fundamental physics and cosmology. I shall discuss the reasons of the persistence of this tension in current physics and then show why in what appears to be a conflict without resolution there is also a stimulating tool for research.

Speaker: Silvia De Bianchi (University of Milan)

17:30 → 18:00 Coffee Break

18:00 → 19:00 Open Discussion

Convener: Roberto Capuzzo Dolcetta (Dep. of Physics, Sapienza, Univ. of Roma)