Background
Martin Hans Christian Knudsen was born on February 15, 1871, in Hasmark, Denmark. His parents, Jorgen Knudsen and Maren Kirstine Hansdatter Fredberg, owned a small estate, and he led the healthy and simple existence of a country boy.
University of Copenhagen, Copenhagen, Denmark
Knudsen showed outstanding abilities in his youth, and upon entering the University of Copenhagen in 1890, he began to study physics, mathematics, astronomy, and chemistry. In 1896 he was granted the Master of Science degree, with physics as his main subject.
University of Copenhagen, Copenhagen, Denmark
Martin Knudsen at work in a laboratory.
Group photo of Martin Knudsen and other scientists.
1936
National Academy of Sciences, Washington, District of Columbia, United States
Knudsen received the Alexander Agassiz Medal of the U.S. National Academy of Sciences in 1936.
1936
National Academy of Sciences, Washington, District of Columbia, United States
Knudsen received the Alexander Agassiz Medal of the U.S. National Academy of Sciences in 1936.
University of Copenhagen, Copenhagen, Denmark
Knudsen showed outstanding abilities in his youth, and upon entering the University of Copenhagen in 1890, he began to study physics, mathematics, astronomy, and chemistry. In 1896 he was granted the Master of Science degree, with physics as his main subject.
University of Copenhagen, Copenhagen, Denmark
Martin Knudsen at work in a laboratory.
Group photo of Martin Knudsen and other scientists.
https://www.amazon.com/TheKineticTheory-Gases-Second-Martin-Knudsen/dp/B01MTBKOD6/?tag=2022091-20
1946
Martin Hans Christian Knudsen was born on February 15, 1871, in Hasmark, Denmark. His parents, Jorgen Knudsen and Maren Kirstine Hansdatter Fredberg, owned a small estate, and he led the healthy and simple existence of a country boy.
Knudsen showed outstanding abilities in his youth, and upon entering the University of Copenhagen in 1890, he began to study physics, mathematics, astronomy, and chemistry. In 1896 he was granted the Master of Science degree, with physics as his main subject. In 1895 Knudsen had answered one of the prize questions posed by the University of Copenhagen on electrical sparks and had received the university’s gold medal.
In 1901 the position of docent was established so that Knudsen could teach physics to medical students. When C. Christiansen retired in 1912, Knudsen succeeded him as professor of physics, a position he held until 1941, when he retired. He also taught at the Technical University.
Knudsen’s scientific work was centered mainly on the properties of gases at low pressure; and using simple methods he obtained important results for further development as well as for the technology of the vacuum. In one of his earliest projects he examined the escape of gases through a small hole and obtained a confirmation of the correctness of the predictions of the kinetic molecular theory; in particular he was responsible for the first indirect experimental confirmation of Maxwell’s law of the distribution of velocity, the experimental determination of the flow of gases through the small hole being in accordance with the formula calculated on the basis of Maxwell’s law.
At the same time Knudsen conducted a study of the flow of gases through narrow tubes and thus arrived at the laws of molecular diffusion. He used an elegant application of diffusion to describe the vapor pressure of mercury at low temperature. Continuing this research, he next examined the behavior of a gas at low pressure in a container in which there is a temperature gradient. This led to a quantitative theory of the “radiometer forces” at low pressure and the discovery of the absolute manometer, now commonly called the Knudsen manometer. Knudsen was also responsible for an extensive series of basic investigations into the behavior of gases at very low pressures and found that it is not the mean free path of the molecules following collisions, but the dimension of the container, which is decisive.
Knudsen also occupies an important place in hydrography. He developed methods to define the various properties of seawater and was very active as an administrator. It was mainly through his initiative that the Central Committee for Oceanic Research of the International Council for Exploration of the Sea was based in Copenhagen. From 1902 to 1947 he was the Danish delegate to the council, the last fourteen years serving as vice-president, and he edited the Bulletin hydrografique from 1908 to 1948.
Besides his work as a researcher and administrator Knudsen carried a heavy load as teacher of physics at the University of Copenhagen and the Polytechnical Institute.
Martin Knudsen went down in history as a pioneer in work on kinetic-molecular theory and low-pressure phenomena in gases. His name is associated with the Knudsen flow, Knudsen diffusion, Knudsen number, Knudsen layer and Knudsen gases. Also there is the Knudsen equation; two instruments, the Knudsen absolute manometer and Knudsen gauge; and one gas pump that operates without moving parts, the Knudsen pump. He was also very active in physical oceanography, developing methods of defining properties of seawater.
He received many honors, both Danish and foreign, for his research and administrative achievements, including the Alexander Agassiz Medal of the U.S. National Academy of Sciences in 1936. He was also nominated eight times for the Nobel Prize in Physics.
Knudsen was a member of the Royal Prussian Academy of Sciences, the German Academy of Sciences, Gottingen Academy of Sciences, and the Royal Danish Academy of Sciences and Letters.
Knudsen was well liked and respected by all his colleagues.
Knudsen was married to Ellen Ursin, and the couple had five children.
