J. Hans Jensen (1965) - Change in meaning of the term 'elementary particle' (German presentation)

J. Hans Jensen (1965)

Change in meaning of the term "elementary particle" (German presentation)

J. Hans Jensen (1965)

Change in meaning of the term "elementary particle" (German presentation)

Comment

Jensen, who studied physics, mathematics, physical chemistry, chemistry and philosophy in Hamburg and Heidelberg, later worked as a theoretical physicist, investigating the structure of atomic nuclei amongst other things. In his 1965 Lindau lecture, which he gave merely two years after receiving the Nobel Prize, he gives an overview of the historical change of meaning of the term “elementary particle”. This change of meaning was very profound indeed, despite the fact that the definition of the term remained practically unchanged since ancient times: an elementary particle cannot be divided or broken up any further and hence represents a basic building block of the matter in our universe.
However, since the beginning of the 20th century, scientists developed impressive skills in breaking up particles which were considered elementary before. And so, quite a few particles had to be disqualified from the “elementary” group. The first one of them was the atom itself (the word atom translates to “the indivisible” in ancient Greek), which was shown to consist of electrons, neutrons and protons in the first decades of the 20th century. What seems to be unfortunate from the perspective of the particle was usually very fortunate for the involved scientists: various discoveries in the field of elementary and subatomic particles were rewarded with Nobel Prizes (for an overview please refer to the Mediatheque Topic Cluster Subatomic Particles). And the quest is still ongoing. Just one year before Jensen’s talk (unmentioned by him in his lecture), the Higgs-boson was postulated as a new elementary particle. In fact, to date, the Higgs-boson has remained the only widely accepted elementary particle, which has never been detected experimentally. Currently (02/2012) more than 10.000 international scientists are working on the ATLAS and CMS experiments of CERN’s Large Hadron Collider (LHC) to change that.
Looking at the scientific developments since Jensen’s Lindau lecture, the rather philosophical questions he raises towards the end of his talk seem even more relevant. Will there be a “never-ending regress”? Will we, by building more and more powerful particle accelerators, go on to discover heavier and heavier elementary particles without limits and bounds? Jensen obviously harboured doubts concerning the more optimistic beliefs of some of his contemporaries, who were hopeful that a comprehensive and closed theory of elementary particles could be found. From a today’s perspective, however, the optimists appear to have ended up being right, since the Standard Model of only three families of quarks and leptons remains so successful.

David Siegel

Rate this content

 (<5 ratings)

Cite


Specify width: px

Share

Rate this content

 (<5 ratings)

Cite


Specify width: px

Share