Julius Johann Phillipp Ludwig Elster (24 December 1854 in Blankenburg – 6 April 1920) was a teacher and physicist.
The personal friendship was deepened by the shared interest in the natural sciences during their years at university in Heidelberg and Berlin.
In 1881 they were working together at the Herzogliche Große Schule (translation: Ducal Great School) in Wolfenbüttel and used their leisure for experimental research.
In April 1920, the Privy Councilor Julius Elster died in Bad Harzburg during a spa stay.
Together with his friend Hans Geitel, he has well over 100 publications on atmospheric electricity, the intensity of the starlight, ihe problems of ionizing radiation (example: "On the radioactivity of the earth substrate and its possible relationship to the geothermal") and other important areas of research a valuable contribution paid to the development of physics.