Sisir Kumar Mitra (or Shishirkumar Mitra) MBE, FNI, FASB, FIAS, FRS (24 October 1890 – 13 August 1963) was an Indian physicist. Early life and education Mitra was born in his father's hometown of Konnagar, a suburb of Kolkata (then Calcutta) located in the Hooghly District in the Bengal Presidency (present-day West Bengal). He was the third son of Joykrishna Mitra, who was a schoolteacher at the time of Mitra's birth, and Saratkumari, a medical student whose family came from Midnapore. While Mitra's paternal family were orthodox Hindus, his mother's family were adherents of the progressive Brahmo Samaj, and were noted in Midnapore for their advanced outlook. In 1878, Joykrishna Mitra had joined the Brahmo Samaj and married his wife, against the wishes of his family, who responded by severing ties with him. As a consequence, the newly wed couple moved to Saratkumari's hometown of Midnapore, where Joykrishna and his wife had two sons – Satish Kumar and Santosh Kumar – and a daughter before Joykrishna moved his family to Kolkata in 1889; there, he became a schoolteacher. Mitra was born the following year. While in Kolkata, Joykrishna became acquainted with several distinguished scholars, notably Ishwar Chandra Vidyasagar and Bipin Chandra Pal. Sharing Saratkumari's progressive outlook, Joykrishna secured his wife's admission as a student at Campbell Medical College. In 1892, Saratkumari qualified as a physician and received an appointment at the Lady Dufferin Hospital in the city of Bhagalpur, then in the Bengal Presidency (now in Bihar). The family thus moved to Bhagalpur, where Saratkumari began her new career, with Joykrishna securing a position as a municipal clerk. A third son, Mitra's younger brother Sarat Kumar, was born at Bhagalpur shortly after. In Bhagalpur, Mitra began school at the Bhagalpore Zilla School. Around 1897–1898, when aged six or seven, his interest in atmospheric science began after hearing the story of Ramchandra Chatterjee, a Bengali aeronaut who a year before Mitra's birth, on 4 May 1889, had become the first Indian to make a solo balloon flight. The story prompted Mitra to ask his elder brother Satish Kumar about the principles of lighter-than-air flight; his brother explained as best as he could. A few years afterwards, both of Mitra's elder brothers died; following this harsh blow, Joykrishna soon suffered a paralytic attack and became an invalid. Despite the family's increasing financial burdens, Saratkumari managed to educate her two surviving sons. During