The professor of physics Gustaf Hällström (1775 – 1844) began his long career (1801 – 1844) already in the era when Finland was under Swedish rule. He experienced the last years of the University in Turku, and the first years of the Alexander University, so named after the University was transferred to the new capital Helsinki. He was a visible opinion leader both in physics and in university administration. Hällström was the last physics professor to derive his salary from a particular parish in Finland, and also the last to be a member of the cathedral chapter. He is known for his investigations in the thermal expansion of matter, especially water. Furthermore he did research in acoustics, meteorology and astronomy. Gustaf Hällström established the position of astronomy as an independent subject. The construction of an astronomical observatory in Turku started in 1817, and the same year the office of an astronomical observer was founded. This office later developed into the University’s first professorship in astronomy.
Hällström participated in the renovation of the University statutes, which became effective in 1828, when the University was transferred to Helsinki. He also participated in the planning of the move. During his first years in Helsinki Hällström held the position of the Rector (1829 – 1832). The subject of physics was located in the new main building of the University, where Hällström founded a physics laboratory
The Department of Physics was formally established in 1832, when the construction of the University main building was complete. In the early 1840’s the Department moved to more spacious rooms in the new building complex of the university library. A new astronomical observatory was built on the present-day Observatory Hill (Tähtitorninmäki) after the University’s move to Helsinki. The University received and accepted this building in 1834.
The first building which was specially designed for the Department of Physics was built in the Siltavuorenpenger zone in central Helsinki. It was inaugurated in 1911. Apart from the new building, the subject of physics had been strengthened in 1895 by another chair of physics, one of applied physics. In 1937 a Swedish-language chair of physics was founded, based on the new language law and decree, according to which the language of instruction and administration in the University of Helsinki was Finnish.
The increase in the number of students starting in the late 1940’s led to the founding of new professorships. Between 1958 and 1977, four new professorships were founded in addition to the three existing ones. An extraordinary personal professorship was founded for meteorology in 1921, with connection to physics. The first ordinary professorship for meteorology was founded in 1957. Between 1957 and 2001, the Department of Meteorology was located in the downtown Porthania building. The chair of geophysics was founded in 1966, and geophysics was its own department from 1967 to 2001. In 1952 a Radio Astronomical Station was accommodated by the Department of Physics. Later it was renamed as the Astrophysics Laboratory and in the beginning of the 1970’s merged to the Department of Astronomy, together with the Observatory. A chair in nuclear physics, founded in 1958, was redefined in 1978 as a chair of elementary particle physics. A professor- ship of theoretical physics was founded in 1964, and theoretical physics had its own department from 1969 to 1995. A new building for theoretical physics was erected in Siltavuorenpenger in 1969, adjacent to the old Physics building. The new building also accommodated the Department of Nuclear Physics, renamed the Department of High Energy Physics in 1978.
The accelerator of the Department began its operation in 1956. It was located in 1959 in a new extension of the Physics building in Siltavuorenpenger. A new accelerator was located in an entirely new building in Kumpula in 1982, when the Accelerator Laboratory was also officially founded. This was the first step in the building of the new university campus in Kumpula.
After 90 years in the downtown location of Siltavuorenpenger, the Physics Department moved in 2001 to its new building, Physicum, in the Kumpula campus. At the same time, the Departments of Meteorology and Geophysics also moved to Physicum and were merged with the Physics Department. The new Department of Physical Sciences was formed, the name of which was changed to Department of Physics in the beginning of 2008. After the year 1998 the research fields of the present Department of Physics have expanded significantly. As an indication of this, the number of professors and chairs has nearly doubled. The Department of Astronomy was merged with the Department of Physics in the beginning of 2010, when all teaching and research of astronomy were moved to the Kumpula campus.