Martin Hans Christian Knudsen (15 February 1871 in Hasmark on Funen[1] – 27 May 1949 in Copenhagen) was a Danish physicist who taught and conducted research at the Technical University of Denmark.
Knudsen received the University's gold medal in 1895 and earned his master's degree in physics the following year.
Knudsen was renowned for his work on kinetic-molecular theory and low-pressure phenomena in gases.
Knudsen was also very active in physical oceanography, developing methods of defining properties of seawater.
By means of his for the purpose constructed precision thermometer, capable of measuring water temperature in the deep sea with a precision of 1/100°C, it was demonstrated that the water masses at the sea floor north of the Wyville Thompson Ridge were consistently a few degrees colder than south of the ridge and likely explained the differences in the deep sea fauna on either sides of the ridge.