Audiobook · read by volunteers
On the Elementary Electrical Charge
Robert Andrews Millikan (1868–1953)
Read by Eric Ray · 3 chapters · 1 h 30
About the book
How small is the smallest unit of electric charge, and how can it be measured? In this scientific paper from 1913, Robert Andrews Millikan reports experiments that refine the famous oil-drop method for determining the charge of the electron. Tiny droplets of oil, hanging in an electric field, are watched through a microscope, and the way they rise and fall reveals the value of the elementary charge with a precision that earlier work could not reach. Millikan explains the improvements he made and discusses what they mean for physics and for the number of molecules in a given quantity of gas. The paper is divided into three parts, read by one LibriVox volunteer in about an hour and a half. It will appeal to students of physics and to anyone curious about how a fundamental constant was pinned down.
Introduction
Robert Andrews Millikan, who lived from 1868 to 1953, was an American physicist, born in Illinois, who taught for years at the University of Chicago before leading the California Institute of Technology. He is remembered above all for his measurement of the charge carried by the electron, work for which he received the Nobel Prize in Physics in 1923. The paper recorded here, On the Elementary Electrical Charge, dates from 1913, appeared in the journal Physical Review and reports the experiments that made his reputation.
It belongs to non-fiction and science, and it is a research paper rather than a popular book. His aim was to improve the oil-drop method of finding the electronic charge, and with it the number of molecules in a given volume of gas, so as to reach an accuracy not achieved before. The method observes minute droplets of oil as they move in an electric field and uses their motion to calculate the charge on them.
The text includes technical description, reasoning and numerical results, so it asks for attention, but its logic is clear and the experimental idea is a beautiful one. The three recorded parts follow the numbered sections of the paper, covering sections one to four, five to eight and nine to thirteen.
A single LibriVox volunteer reads the whole piece in about an hour and a half. Today it is worth hearing as a primary source in the history of physics, to see how a careful experiment is built, argued and presented, and to appreciate the patience behind a number now taken for granted.
Public domain
Robert Andrews Millikan died in 1953: the work is in the public domain in Switzerland, more than 70 years after the author’s death.
The LibriVox volunteers dedicated this recording to the public domain.
Sources : LibriVox page · Files at the Internet Archive · Original text