International Union of the History and Philosophy of Science

Joint DHS-DLMPS Commission

XIVth DHS-DLMPS Joint Conference

Probability and physical reality

Brussels, Palais des Académies on Friday the 19th November 2004 at 9h30

The first person to have the idea of applying probabilities to physics was Daniel Bernoulli in an article on the inclination of planetary orbits with respect to the ecliptic. The probability of finding all the inclination angles to be smaller than
9° is so small that Daniel deduces that this phenomenon must have a cause. This way of reasoning will have a strong influence on Laplace who uses it in his first work.
We also owe the model of gas which allows a statistical treatment to Daniel Bernoulli. This idea was then independently rediscovered by Waterston, and Krönig, whereas Maxwell and Boltzman went back to Bernoulli’s text. Boltzman brought a big change by giving a probabilistic definition of Clausius’ entropy.
Quantum mechanics was born with both Planck and Einstein in the context of statistical mechanics and one knows the problems that this brought for Einstein.

In this colloquium, we shall question the way in which the main protagonists of statistical mechanics, quantum mechanics and more generally those who apply probabilities to physics have conceive the relationship between their theories and reality. A mathematical tool which allows a first approach but which must be disregarded in order to obtain a theory which completely describes reality, seems to be the view of Laplace as well as Einstein. A tool which does not differentiate itself, in its description of reality, from the other mathematical tools would be the view of the Copenhagen school. However, between these two extreme points of view, there are many intermediary positions.

Programme

9h30 Welcome, R. Halleux (Liège) and E. Neuenschwander (Zürich)
Introduction, Patricia Radelet-de Grave (UCL)

10h00 Helge Kragh (Aarhus),

• Probabilistic physics and the puzzle of radioactivity

11h00 Break

11h15 Christian Maes (KULeuven),

• Time-reversing quantum probabilities : the issue of reversibility and retrodiction in quantum mechanics

12h15 Break

14h30 Domenico Costantini and U. Garibaldi (Genova)

• Due-to-ignorance and factual probabilities : a probabilistic view on physical reality

15h30 Jean Bricmont (UCL),

• The real problem of probabilities in quantum mechanics. Or what did Bell realy say.

16h30 Break

16h45 Jean Dhombres (EHESS et CNRS Paris),

• L'incertitude des analystes et l'incertitude des probabilistes à l'épreuve de la physique au XXe siècle

17h45 Conclusion , Erwin Neuenschwander (Zürich)

Organizing Committee

a) Belgian Members

Patricia Radelet-de Grave (UCL)
Robert Halleux (ULg)

Christian Maes (KULeuven)

b)Foreign Member

Erwin Neuenschwander (Zürich)

Scientific Program Committee

a) Belgian Members

Patricia Radelet-de Grave (UCL)
Robert Halleux (ULg)
Christian Maes (KULeuven)
Jean Bricmont (UCL)
Jean Mawhin (UCL)
Fernand Hallyn (RUG)
Dominique Lambert (FUNDP)
Christian Radoux (UMH)
Jos Uyttenhove (RUG)

b)Foreign Members

Erwin Neuenschwander (Zürich)
Jean Dhombres, EHESS et CNRS (Paris)