Antanas Sližys was born into a farmers’ family in Atkočiškis village, Skiemonys rural district, Utena county. In 1936, Antanas finished primary school, and in 1943 a gymnasium. At school he became interested in astronomy, physics, and mathematics. In 1944, Antanas entered Kaunas Theological Seminary where he studied for two years. He then changed his mind and in 1947 became a student at the Astronomy Department of the Faculty of Physics and Mathematics of Vilnius University. He was not fated to graduate as he was deported in 1949. Antanas Sližys returned to Lithuania in 1955. The documents in his personal file do not make it possible to reconstruct the sequence of events. Upon return from exile, Antanas was given the opportunity to do correspondence studies at the Faculty of Physics and Mathematics, but in 1956 he was issued an academic reference note indicating that he had been a student at Vilnius University until 1949. For reasons unknown he did not resume his studies.