Charles Greeley Abbot (May 31, 1872 – December 17, 1973) was an American astrophysicist, astronomer and Secretary of the Smithsonian Institution. He was born in Wilton, New Hampshire.

Abbot graduated from MIT in 1894 with a degree in chemical physics. Samuel Pierpont Langley was looking for an assistant at the Smithsonian Astrophysical Observatory, and hired Abbot in 1895 because of his skill at laboratory work, despite his lack of experience in astronomy.

Langley began to focus on aeronautics experiments, and Abbot took responsibility for the observatory's solar observations. He designed and built devices for measuring solar radiation, including a greatly improved bolometer which was used to measure the Sun's inner corona at the 1900 solar eclipse in Wadesboro, North Carolina.

Langley died in 1906. Abbot succeeded him as director of the SAO, and Charles Walcott became Smithsonian secretary. Abbot soon used improved techniques to come up with a more accurate value of 1.93 cal/cm²/min for the solar constant (the modern value is measured in watts per square meter).

Abbot won the Henry Draper Medal of the National Academy of Sciences in 1910 and the Rumford Prize of the American Academy of Arts and Sciences in 1915.

Abbot pushed to provide funding to rocket pioneer Robert Goddard during World War I, but to his disappointment this was canceled after the end of the war.

In 1918 Abbot became Assistant Secretary of the Smithsonian. He succeeded Walcott as Secretary in 1928, and guided the Smithsonian through turbulent times during the Great Depression and World War II. He retired as both SAO director and Smithsonian Secretary in 1944, being the first Smithsonian Secretary not to die in office.

Abbot, like Langley, pursued the idea that the Sun's radiation was variable and that this variability could influence weather. He persistently searched for variations in the solar constant, hoping that these could be used for weather forecasting, and believed that he had detected such variations, on the order of 3% to 10%. However, modern measurements of greater accuracy indicate that such variability does not occur, apart from tiny variations due to sunspots and faculae.

He delegated the National Museum largely to his Assistant Secretary, Alexander Wetmore, who succeeded him as Secretary in 1944.

Abbot crater on the Moon is named after him; an exception was made and it was named for him while he was still alive. He obtained his last patent at the age of 101, the oldest inventor to ever receive a patent.

External links

• National Academy of Sciences biography

Obituaries

• QJRAS 18 (1977) 136