Gustaf Wilhelm Hammar

{{Short description|American physicist (1893–1954)}}

Gustaf Wilhelm Hammar (Gustav Vilhelm Hammar) (June 22, 1893 – August 19, 1954) was a Swedish-born American experimental physicist.{{cite journal|title=Gustaf W. Hammar (obituary)|journal=Physics Today|year=1954|volume=7|issue=12|pages=22|doi=10.1063/1.3061470}} He was the eldest of six children of Anders Vilhelm Hammar and Elin Christina Hammar (née Olsson).{{cite web|last=Andersen|first=Bent Breiner|title=Gustaf W. Hammar|url=http://www.myheritage.dk/person-1001365_134962721_134962721/gustaf-w-hammar|publisher=MyHeritage|accessdate=21 December 2012}} He emigrated to the United States in 1913, attended Bethel University in St. Paul, Minnesota,{{cite journal|title=Alumni News|journal=The Bethel Clarion|date=December 10, 1932|volume=12|issue=3|pages=4|url=http://cdm16120.contentdm.oclc.org/cdm/singleitem/collection/p15186coll6/id/3600/rec/3|accessdate=21 December 2012}} and by 1920 was married and living with his wife, Louise (with whom he was ultimately to have four children), in King County, Washington.

He obtained his M.S. degree at the University of Idaho in 1924{{cite web|last=Hammar|first=Gustaf William|title=Thermal conductivities of a few insulators at various temperatures|url=http://en.scientificcommons.org/6196436|publisher=ScientificCommons|accessdate=21 December 2012}}{{Dead link|date=June 2024 |bot=InternetArchiveBot |fix-attempted=yes }} and a Ph.D. from the California Institute of Technology in 1927. His Ph.D. dissertation topic was titled "Magnetic Susceptibilities of Some Common Gases."{{Cite journal|last=Hammar|first=Gustaf Wilhelm|title=Magnetic Susceptibilities of Some Common Gases|bibcode=1927PhDT.........5H|publisher=Physics Abstract Service|year=1927}}

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.{{cite journal|title=Personals|journal=Engineering and Science|date=April 1955|volume=18|issue=7|pages=40|url=http://calteches.library.caltech.edu/160/2/ES18.7.1955.pdf|accessdate=21 December 2012}} 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, he and his student Lawrence W. Foskett developed a telephone using light instead of copper wire for transmitting signals.{{cite news |url=https://digital.lib.uidaho.edu/cdm/ref/collection/argonaut/id/676?_ga=2.157349048.343941606.1506404953-374550616.1499903542 |work=Idaho Argonaut |location=(Moscow) |agency=(University of Idaho) |title=University physics head develops light telephone |date=November 3, 1931 |page=1}}{{cite journal|title=I Told You So!|journal=New Mexico Lobo|date=February 26, 1932|volume=34|issue=20|pages=3|url=http://repository.unm.edu/bitstream/handle/1928/14379/Volume%2034,%20No%2020,%202-26-1932.pdf?sequence=1|accessdate=21 December 2012}} At present, however, Hammar is best remembered for an experiment that was quite outside of his main area of research, the Hammar experiment, a test of the validity of special relativity.{{cite journal

| author= G. W. Hammar

| year= 1935

| title= The Velocity of Light Within a Massive Enclosure

| journal= Physical Review

| volume= 48

| issue= 5

| pages= 462–463

| doi= 10.1103/PhysRev.48.462.2

|bibcode = 1935PhRv...48..462H }}{{cite book

| author= H. P. Robertson and Thomas W. Noonan

| year= 1968

| title= Relativity and Cosmology

| contribution=Hammar's experiment

| publisher= Saunders

| location= Philadelphia

| pages= 36–38}}

In 1946, he joined the Eastman Kodak Company as a senior supervising physicist with the Navy Ordnance Division.{{cite journal|title=Personals|journal=Engineering and Science|date=December 1953|volume=17|issue=3|url=http://calteches.library.caltech.edu/149/|pages=40|accessdate=21 December 2012}} 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.{{cite journal|title=Personals|journal=Engineering and Science|date=October 1953|volume=17|issue=1|pages=36|url=http://calteches.library.caltech.edu/148/|accessdate=21 December 2012}}