Charles Greeley Abbot (May 31, 1872 – December 17, 1973) was an American astrophysicist and the fifth secretary of the Smithsonian Institution, serving from 1928 until 1944.

[1][5] His parents, Harris Abbot and Caroline Ann Greeley, were farmers and he was the youngest of four children.

[5][6] As a youth he built and invented numerous things, such as a forge to fix tools, a water wheel to power a saw, and a bicycle.

During his expedition experiences he would also travel to Algeria, Egypt, South Africa, Australia, and other countries, often in partnership with the National Geographic Society.

[1] While Langley was still Director, he had visited Mount Whitney, and decided it would be a great place for an observatory.

[13] In his role as Assistant Secretary he would oversee the Smithsonian Institution Libraries, the International Exchange Service, and the SAO.

[5] Ten years later, on January 10, 1928, he became the fifth Secretary of the Smithsonian after the death of Charles Doolittle Walcott.

In 1927, Walcott had finalized the Smithsonian's strategic plan, which Abbot took on responsibility for upon his election as Secretary.

Abbot's role in the United States National Museum was also minimal, and was under the primary care of Assistant Secretary Alexander Wetmore.

Following retirement, he was awarded Secretary Emeritus status[1] and proceeded to continue his research work.

The event was held at the Smithsonian Castle and a bronze bust of Abbot, by Alicia Neatherly, was presented, and donated to the National Gallery of Art.

With this research he hoped to track solar constant in order to make weather pattern predictions.

One balloon returned data that allowed Abbot to determine the solar constant at the highest point of the Earth's atmosphere.