astronomy

Martin Knudsen

Martin Knudsen is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Martin Knudsen rather than just read about it. In short: Martin Hans Christian Knudsen (15 February 1871 in Hasmark on Funen – 27 May 1949 in Copenhagen) was a Danish physicist who taught and conducted research at the Technical University of Denmark. He is primarily known for his study of molecular gas flow and the development of the Knudsen cell, which is a primary component of molecular beam epitaxy systems.

Key takeaways

Martin Knudsen belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Martin Knudsen to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Martin Knudsen from memory before moving on to harder problems.

Reference excerpt

Martin Hans Christian Knudsen (15 February 1871 in Hasmark on Funen – 27 May 1949 in Copenhagen) was a Danish physicist who taught and conducted research at the Technical University of Denmark. He is primarily known for his study of molecular gas flow and the development of the Knudsen cell, which is a primary component of molecular beam epitaxy systems. Knudsen received the university's gold medal in 1895 and earned his master's degree in physics the following year. He became lecturer in physics at the university in 1901 and professor in 1912, when Christian Christiansen (1843–1917) retired. He held this post until his own retirement in 1941. Knudsen was renowned for his 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. His book, The Kinetic Theory of Gases (London, 1934), contains the main results of his research. Knudsen was also very active in physical oceanography, developing methods of defining properties of seawater. He participated as hydrographer on the Ingolf expedition in the North Atlantic in 1895-96. 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. He was editor of Hydrological Tables (Copenhagen–London, 1901). In 1927, he was one of the participants of the fifth Solvay Conference on Physics that took place at the International Solvay Institute for Physics in Belgium. He was awarded the Alexander Agassiz Medal of the U.S. National Academy of Sciences in 1936. He was made a Commander First Class of the Order of the Dannebrog.

References

Literature Matematiken i Danmark (Mathematics in Denmark) by Niels Nielsen, Gyldendalske Boghandel, Nordisk Forlag, København. Vol. I: 1801-1908, published 1910; Vol. II: 1528-1800, published 1912. (In Danish). Note: This important work is a compilation of Danish mathematical writings. In addition to mathematicians, the short biographical notes include many physicists, astronomers, and early natural philosophers, including medical practitioners. Kemien i Danmark (Chemistry in Denmark) by Stig E. Veibel. Vol. I: Kemiens historie i Danmark (The History of Chemistry in Denmark), 1939. Vol. II: Dansk Kemisk Bibliografi, 1800-1935 (Danish Chemistry Bibliography), 1943. Vol III: Danske Kemikere (Danish Chemists), edited by Bodil Jerslev, 1968 (Three of six chapters by Stig Veibel). All published by Nyt Nordisk Forlag, Copenhagen. (In Danish). Note: Vol. II is a compilation of Danish publications in chemistry and includes works by physicists, geologists, biologists, and physicians, along with biographical information. Dictionary of Scientific Biography, Charles Coulston Gillispie, editor, Scribner's & Sons, New York, 1980 (16 Volumes). Supplement of 1990 (Volumes 17 and 18).

Worked examples

Example 1 — a first encounter with Martin Knudsen

Start with the simplest possible case. Write down what Martin Knudsen claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Martin Knudsen before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Martin Knudsen ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Martin Knudsen

In research: Martin Knudsen appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Martin Knudsen in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Martin Knudsen is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1871 births, 1949 deaths, Academic staff of the University of Copenhagen, so understanding it makes those chapters shorter.
In everyday life: Look for Martin Knudsen outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Martin Knudsen in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Martin Knudsen means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Martin Knudsen out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Martin Knudsen in simple terms?

Why does Martin Knudsen matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Martin Knudsen?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Martin Knudsen.