Gustaf Wilhelm Hammar (Gustav Vilhelm Hammar) (June 22, 1893 – August 19, 1954) was a Swedish-born American experimental physicist. He was the eldest of six children of Anders Vilhelm Hammar and Elin Christina Hammar (née Olsson). He emigrated to the United States in 1913, attended Bethel University in

St. Paul, Minnesota Saint Paul (often abbreviated St. Paul) is the capital city of the U.S. state of Minnesota and the county seat of Ramsey County. As of the 2020 census, the city had a population of 311,527, making it Minnesota's second-most populous city a ...

, and by 1920 was married and living with his wife, Louise (with whom he was ultimately to have four children), in

King County, Washington King County is a County (United States), county located in the U.S. state of Washington (state), Washington. The population was 2,269,675 in the 2020 United States census, 2020 census, making it the List of counties in Washington, most populo ...

. He obtained his M.S. degree at the

University of Idaho The University of Idaho (U of I, or UIdaho) is a public land-grant research university in Moscow, Idaho, United States. Established in 1889 and opened three years later, it was the state's sole university for 71 years, until 1963. The un ...

in 1924 and a Ph.D. from the

California Institute of Technology The California Institute of Technology (branded as Caltech) is a private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small group of institutes ...

in 1927. His Ph.D. dissertation topic was titled "Magnetic Susceptibilities of Some Common Gases." He returned to the University of Idaho in 1926 to teach, and became the head of the physics department in 1930, a position that he held for sixteen years. He led a productive materials science laboratory and was mindful of practical applications of his research—for example, as an extension of his researches in

photoelectricity The photoelectric effect is the emission of electrons from a material caused by electromagnetic radiation such as ultraviolet light. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physic ...

, he and his student Lawrence W. Foskett developed a telephone using light instead of copper wire for transmitting signals. At present, however, Hammar is best remembered for an experiment that was quite outside of his main area of research, the

Hammar experiment The Hammar experiment was an experiment designed and conducted by Gustaf Wilhelm Hammar (1935) to test the aether drag hypothesis. Its negative result refuted some specific aether drag models, and confirmed special relativity. Overview Experiment ...

, a test of the validity of

special relativity In physics, the special theory of relativity, or special relativity for short, is a scientific theory of the relationship between Spacetime, space and time. In Albert Einstein's 1905 paper, Annus Mirabilis papers#Special relativity, "On the Ele ...

. In 1946, he joined the

Eastman Kodak Company The Eastman Kodak Company, referred to simply as Kodak (), is an American public company that produces various products related to its historic basis in film photography. The company is headquartered in Rochester, New York, and is incorporated i ...

as a senior supervising physicist with the Navy Ordnance Division. During this period with Kodak, he worked on various military projects. He developed infrared photosensitive cells for use in night-vision gun sights, and time-delayed fuses for use in unattended firearms intended to mislead the enemy into believing that large forces of men are concentrated in areas where they actually are not (patents 2547820, 2601135, 2917413, 2958802, 3063862, 3067330). In 1953, he was honored for his research in physics with fellowship in the

American Physical Society The American Physical Society (APS) is a not-for-profit membership organization of professionals in physics and related disciplines, comprising nearly fifty divisions, sections, and other units. Its mission is the advancement and diffusion of ...

References

{{DEFAULTSORT:Hammar, Gustaf Wilhelm American experimental physicists 1893 births 1954 deaths Swedish emigrants to the United States University of Idaho alumni California Institute of Technology alumni Bethel University (Minnesota) alumni University of Idaho faculty