Group Photograph of Sorensen, Millikan, and other Prominent Scientists at the California Institute of Technology

Group Photograph of Sorensen, Millikan, and other Prominent Scientists at the California Institute of Technology

This is a puzzling rare photograph where Professor Sorensen and Dr. Millikan are captured together. Professor Sorensen, head of the Electrical Engineering department at Caltech and Dr. Millikan, Nobel Prize winning physicist, had worked together to develop the vacuum switch. Sorensen tested and patented, with Millikan’s institutional support, vacuum switches to eliminate the arcing problems at Caltech’s High Volts Lab [3]. While this creation is often highlighted as a solitary endeavor, a patent dispute with Talma Greenwood proves otherwise. In it, Sorensen testified that the vacuum switch was born from our "desire to have a positive mechanical connection between the movable switch electrode and the exterior mechanism," stating that the idea was the "result of long discussions" with Millikan [5]. Sorensen emphasizes this joint collaboration. Millikan also confirmed this, stating the invention "grew out of discussions... going on for two or three years" [5]. Sorensen highlights that he approached Millikan because he knew that “Dr. Millikan has also been studying the phenomena of arcing in a vacuum and that they agreed to operate together in their investigations of this subject” [5]. This collaboration proved immensely valuable as the patent was sold to General Electric in 1930 for $100,000 which is just a little under $2 million today [4].


Works Cited
[1] “100 Years Young: Big Creek Hydroelectric Plant Still Going Strong.” Edison International | Newsroom, https://newsroom.edison.com/stories/100-years-young:-big-creek-hydroelectric-plant-still-going-strong. Accessed 17 Mar. 2026.

[2] “Power Lines Around Los Angeles: Isolation, Interconnection, and Aesthetics.” Boom California, 21 May 2020, https://boomcalifornia.org/2020/05/21/power-lines-around-los-angeles-isolation-interconnection-and-aesthetics/.
[3] Fox, Donna, Robert J. McEliece, and Babak Hassibi. “An Electrifying Century: An Early History of the Caltech EE Department.” ENGenious, 8 Oct. 2010, engenious.caltech.edu/articles/history-EE-Department-century. Accessed 5 Feb. 2026.

[4] Heilbron, J. L., and Robert W. Seidel. Lawrence and His Laboratory: A History of the Lawrence Berkeley Laboratory, University of California Press, 1990. UC Press E-Books Collection, https://publishing.cdlib.org/ucpressebooks/view?docId=ft5s200764&chunk.id=[section
identifier]. Accessed 5 Feb. 2026.

[5] Millikan, Robert A., and Royal W. Sorensen. Brief for Millikan and Sorensen. Robert A. Millikan and Royal W. Sorensen v. Talma T. Greenwood, Interference No. 56557, United States Patent Office, [Year, e.g., 1928], [Collection Name, e.g., Royal W. Sorensen Papers], [Box 3], Caltech Archives, Pasadena, CA.

[6] Ornelas, Gabriela. “Big Creek’s Powerhouse 8 Marks 100 Years of Hydroelectric Power.” Energized by Edison, 8 Oct. 2021, energized.edison.com/stories/big-creeks-powerhouse-8-marks-100-years-of-hydroelectric-power. Accessed 5 Feb. 2026.

[7] Record, Historic American Engineering. Big Creek Hydroelectric System, East & West Transmission Line, 241-Mile Transmission Corridor Extending between the Big Creek Hydroelectric System in the Sierra National Forest in Fresno County and the Eagle Rock Substation in Los Angeles, California, Visalia, Tulare County, CA. Still image. California -- Tulare County -- Visalia, https://www.loc.gov/pictures/item/ca3976/. Accessed 17 Mar. 2026.

[8] Sorensen, Royal W., and Hallan E. Mendenhall. “Vacuum Switching Experiments at California Institute of Technology.” Transactions of the American Institute of Electrical Engineers, XLV, Jan. 1926, pp. 1102–07. Semantic Scholar, https://doi.org/10.1109/T-AIEE.1926.5061306.

Caltech Archives and Special Collections, Royal W. Sorensen Papers (SorensenRW), Box 3

Photograph & Paper

4" x 6"