Summary of Paul A. M. Dirac, Interview by Friedrich Hund (1982)

00:00:00 - 00:20:00

In an interview with physicist Friedrich Hund, Paul Dirac emphasizes the importance of symmetry in physics and how his work on the Dirac equation highlighted this concept. He discusses the unexpected appearance of spin, the treatment of pairs of particles in his theory, and the importance of general relativity. Dirac expresses concern about the current methods used by theoretical physicists such as the renormalization technique and believes that important discoveries need to be made before questions regarding particle theory can be put in order. He also mentions the current investigation of the constant ratio of masses and whether it changes over time.

• 00:00:00 In this section, Paul Dirac and Friedrich Hund discuss the importance of symmetry in theoretical physics, starting from Einstein's realization of the symmetry of space and time and moving on to other symmetries such as that between electron and anti-electron and positive and negative charge. They also discuss how Dirac's work on the Dirac equation of the electron highlighted the importance of symmetry in physics, leading to the development of transformation theory and a new kind of equation.
• 00:05:00 In this section, Paul A. M. Dirac discusses the unexpected appearance of spin in the equation of electrons and how it was a great revelation when it appeared. He also explains how the Dirac theory treats pairs of particles like positrons and electrons in the form of one-particle theory, whereas the Pauli-Weisskopf theory treats pairs of scalar spin particles in a many-body theory. Dirac also touches upon general relativity and its importance in physics, stating that his recent work has been focused on it and how there are theoretical reasons to believe that the times and distances in it are not the same as those provided by atomic clocks.
• 00:10:00 In this section, Paul Dirac discusses the gravitational forces getting weaker compared to electric forces as the world gets older. Observations made accurately on the Moon and on Mars show some evidence of a difference between Einstein time and atomic time, but it is still being studied since many disturbances need to be taken into account. Dirac explains that the best way to define natural time and natural length are atomic time and atomic length, but it might not be the quantities to be used in Einstein theory for astronomical observations, causing uncertainty on its interpretation. He suggests that Einstein's equations remain but should be applied differently, and it is matter of interpretation whether the gravitational constant is a constant or not. Dirac points out that Einstein's theory has been successful but the question of its interpretation is not yet settled.
• 00:15:00 In this section, physicist Paul Dirac discusses the possibility of a unified theory of particles and expresses concern over the current methods used by theoretical physicists, particularly the renormalization technique. Dirac believes that important discoveries need to be made before questions regarding particle theory can be put in order. He notes that the fine-structure constant, which plays an important role in physics, has not been explained and that an explanation is necessary before understanding atomic theory can advance.
• 00:20:00 In this section of the interview, Dirac mentions a current problem being investigated involving the constant ratio of masses and whether it changes over time. He notes that researchers are currently trying to understand this issue.