Alexei Petrovich Sokolov (7.03.1854-26.03.1928) was a Russian physicist. He was born in Kaluga. He graduated from Moscow University (1877) and was kept on at the department of physics to prepare for a professorship. In 1881—82 he worked at the University of Warsaw, and from 1883 at Moscow University (professor from 1884). In 1904 he organised the physics practical course at the Physical Institute of Moscow University, and in 1912 the first radiological laboratory in Russia.
His research concerned mainly radioactivity. He studied the ionisation and radioactivity of air and gases from various sources, and the radioactivity of mineral waters and muds, soils, rocks and minerals. He was the first to note the influence of ionisation and radioactivity on the human body. He studied the internal thermal regime of the Earth in connection with its radioactivity, and put forward (1910) the idea that the Earth's interior continues to heat up from internal sources of heat.