Robert Millikan
Early Life and Education
Robert Andrews Millikan was born on March 22, 1868, in Morrison, Illinois, USA. He was the second son of Reverend Silas Franklin Millikan and Mary Jane Andrews Millikan. Millikan's early education was in the public schools of Maquoketa, Iowa. In 1886, he entered Oberlin College in Ohio, where he initially studied classical languages. However, he soon developed an interest in physics and mathematics, which led him to pursue a career in the sciences.
After graduating from Oberlin in 1891, Millikan became a teaching assistant in physics. He then enrolled at Columbia University in New York City, where he earned his Ph.D. in physics in 1895. His doctoral dissertation focused on the polarization of light emitted by incandescent surfaces, a topic that laid the groundwork for his future research.
Academic Career
Millikan began his academic career as an assistant at the University of Chicago in 1896. He quickly rose through the ranks, becoming an associate professor in 1902 and a full professor in 1910. During his tenure at the University of Chicago, Millikan conducted groundbreaking experiments that would earn him international acclaim.
One of Millikan's most significant contributions to physics was his work on the photoelectric effect. Building on the theories of Albert Einstein, Millikan conducted a series of experiments that confirmed the quantized nature of light. His meticulous measurements provided empirical support for Einstein's theory, which posited that light consists of discrete packets of energy called photons.
The Oil Drop Experiment
Millikan is perhaps best known for his oil drop experiment, which he conducted between 1909 and 1913. This experiment aimed to measure the elementary electric charge, or the charge of the electron. Millikan and his colleague, Harvey Fletcher, used a device that sprayed tiny oil droplets into a chamber. By applying an electric field, they were able to balance the gravitational and electric forces acting on the droplets, allowing them to measure the charge with unprecedented accuracy.
The oil drop experiment provided the first precise measurement of the electron's charge, which Millikan determined to be approximately 1.602 x 10^-19 coulombs. This result was a pivotal moment in the field of atomic physics, as it confirmed the quantized nature of electric charge and provided a fundamental constant for future research.
Later Research and Contributions
After his success with the oil drop experiment, Millikan turned his attention to other areas of physics. He conducted extensive research on cosmic rays, high-energy particles originating from outer space. Millikan coined the term "cosmic rays" and proposed that they were primarily composed of high-energy protons. His work in this area helped to establish the field of astroparticle physics.
In addition to his experimental work, Millikan was a prolific author and educator. He wrote several influential textbooks, including "The Electron" (1917) and "Electrons (+ and -), Protons, Photons, Neutrons, and Cosmic Rays" (1935). These works were widely used in physics education and contributed to the dissemination of modern scientific knowledge.
Awards and Honors
Millikan's contributions to physics were widely recognized during his lifetime. In 1923, he was awarded the Nobel Prize in Physics for his work on the elementary charge and the photoelectric effect. He also received numerous other honors, including the National Medal of Science and the Franklin Medal.
Millikan served as the president of the American Physical Society and was a member of several prestigious scientific organizations, including the National Academy of Sciences and the Royal Society of London. His leadership and advocacy for scientific research had a lasting impact on the development of physics in the United States.
Personal Life and Legacy
Millikan married Greta Ervin Blanchard in 1902, and the couple had three sons: Clark Blanchard, Glenn Allen, and Max Franklin. Millikan was known for his dedication to both his family and his work, often balancing his scientific pursuits with his responsibilities as a husband and father.
Robert Millikan passed away on December 19, 1953, in San Marino, California. His legacy endures through his numerous contributions to physics and his role in shaping modern scientific thought. Millikan's precise measurements and innovative experiments laid the foundation for many of the advancements in atomic and particle physics that followed.