Jacob Clay () (January 18, 1882–December 31, 1955) was a prominent Dutch physicist who first suggested and provided evidence that cosmic rays are charged particles.

Early life

Clay was born "Jacob Claij" in

Berkhout Berkhout is a village in the northwest Netherlands. It is in the municipality of Koggenland, North Holland, about west of Hoorn. History The village was first mentioned around 1312 as Berchout, and means "deciduous forest of birch (''Betula'' ...

on 18 January 1882 as the son of Pieter Claij and Neeltje Molenaar. After attending the

Erasmiaans Gymnasium The Gymnasium Erasmianum is a school in Rotterdam (also known under its Dutch name "Erasmiaans Gymnasium"). History Founded in 1328, it is the second oldest school in the Netherlands with recorded date of establishment (after the Johan de Witt-g ...

, he studied physics at the University of Leiden under Heike Kamerlingh Onnes and Hendrik Antoon Lorentz. After obtaining his Ph.D. degree in 1908 he married

Tettje Clay-Jolles Tettje Clay-Jolles (1881–1972) was one of the first female Dutch physicists. She studied the variation of atmospheric radiation with geographic latitude. Early life Clay-Jolles was born in 1881 in Assen, Netherlands to Eva Dina Halbertsma and ...

with whom he had a son.

Career

After teaching in Leiden and at the Technische Hogeschool in

Delft Delft () is a List of cities in the Netherlands by province, city and Municipalities of the Netherlands, municipality in the Provinces of the Netherlands, province of South Holland, Netherlands. It is located between Rotterdam, to the southeast, ...

from 1906 to 1920, he was appointed Professor at the newly founded Bandung Institute of Technology. Clay collaborated with his wife

on research which discovered that atmospheric radiation varies according to geographic latitude. On a trip back to the Netherlands he measured the

cosmic radiation Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...

and noticed an increase the further he was from the equator, which suggested to him that cosmic rays are deflected by the geomagnetic field and let him to propose that they are charged particles rather than photons. This proposal was generally accepted by 1932. In 1929 he became professor at the University of Amsterdam, publishing over 200 papers until his retirement in 1952. In 1928 he became correspondent of the

Royal Netherlands Academy of Arts and Sciences The Royal Netherlands Academy of Arts and Sciences ( nl, Koninklijke Nederlandse Akademie van Wetenschappen, abbreviated: KNAW) is an organization dedicated to the advancement of science and literature in the Netherlands. The academy is housed ...

, he resigned a year later. In 1936 he became a full member. Clay died on 31 December 1955 in De Bilt

Personal life

Clay met and fell in love with Tettje Jolles, a fellow PhD student, and in 1908 the two were married. They had three children. In 1920, the family moved to

Bandung Bandung ( su, ᮘᮔ᮪ᮓᮥᮀ, Bandung, ; ) is the capital city of the Indonesian province of West Java. It has a population of 2,452,943 within its city limits according to the official estimates as at mid 2021, making it the fourth most ...

, Java when Jacob Clay was hired as a professor of physics at the Institute of Technology.

References

* H.F.Jongen
Claij, Jacob (1882-1955)
in

Biografisch Woordenboek van Nederland The ''Biografisch Woordenboek van Nederland'' (BWN) is a Dutch biographical dictionary, in which short biographies of well-known and less well-known but still notable Dutch people are listed. The BWN is the successor to the ''Nieuw Nederlandsch ...

. 2-11-2013 {{DEFAULTSORT:Clay, Jacob 1882 births 1955 deaths People from Koggenland 20th-century Dutch physicists 20th-century Dutch philosophers Leiden University alumni University of Amsterdam faculty Bandung Institute of Technology faculty Members of the Royal Netherlands Academy of Arts and Sciences Fellows of the American Physical Society