astronomy

Knud Jessen

Knud Jessen 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 Knud Jessen rather than just read about it. In short: Knud Jessen (29 November 1884 – 14 April 1971) was a Danish botanist and quaternary geologist. Biography Jessen was born at Frederiksberg, Denmark.

Key takeaways

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

Reference excerpt

Knud Jessen (29 November 1884 – 14 April 1971) was a Danish botanist and quaternary geologist.

Biography Jessen was born at Frederiksberg, Denmark. He was a student at the University of Copenhagen and was awarded cand.mag. in natural history and geography with botany as a major in 1911. He was state geologist 1917–1931. In 1931, he succeeded C.H. Ostenfeld as professor of botany at the University of Copenhagen and director of the Copenhagen Botanical Garden, a position he held until his retirement in 1955. His scientific works mainly concern vegetation history during the Eemian interglacial, the late glacial period of the Wisconsin glaciation and in the Holocene investigated using pollen analysis. Jessen had come into contact with the Irish naturalist Robert Lloyd Praeger and made field-work on the quaternary geology of Ireland during 1934-1935. Together with his assistant, Frank Mitchell, he was able to describe both the post-glacial vegetation development of Ireland and that of the Eemian interglacial, with the presence in Ireland of such plants as Rhododendron ponticum, Abies alba, Erica scoparia and Buxus sempervirens. Jessen was acknowledged by honorary doctorates at the University of Cambridge and University of Dublin. He was a member of the Royal Danish Academy of Sciences and Letters and served on the board of directors of the Carlsberg Foundation. Jessen also lived in the Botanical Gardens in his later life. He became a Knight in the Order of the Dannebrog in 1936 and Commander 2nd degree in 1949.

Personal life Jessen married Ingrid Holm (1884-1984) and had four children, including Poul Holm Jessen, a chemist who founded and ran the plastics company Scandiflex.

Selected scientific works Jessen, K. (1920) Moseundersøgelser i det nordøstlige Sjælland. Med Bemærkninger om Træers og Buskes Indvandring og Vegetationens Historie (Bog investigations in Northeast Zealand with notes on the immigration of trees and shrubs and the development of the vegetation). Doctoral dissertation. Danmarks Geologiske Undersøgelse, II.række, 34, 1-243. Jessen, Knud; Lind, Jens (1922). Det danske Markukrudts Historie [History of Danish Arable Weeds]. Kongelige Danske Videnskabernes Selskabs Skrifter - Naturvidenskabelig og Mathematisk Afdeling, 8.Rk. (in Danish). Vol. 8. p. 496. Jessen, K. & V. Milthers (1928) Stratigraphical and palaeontological studies of interglacial fresh-water deposits in Jutland and northwest Germany. Danmarks Geologiske Undersøgelser II rk. Vol. 48: 1-379. Jessen, K. with the assistance of H. Jonassen (1935) The composition of the forests in northern Europe in Epipalaeolithic time. Biologiske Meddelelser, Kongelige Danske Videnskabernes Selskab 12 (1): 1-64. Jessen, K. (1949) Studies in Late Quaternary deposits and flora-history of Ireland. Proceedings of the Royal Irish Academy 52, sect. B, no. 6: 85-290.

References

Illustrations

Worked examples

Example 1 — a first encounter with Knud Jessen

Start with the simplest possible case. Write down what Knud Jessen 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 Knud Jessen 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 Knud Jessen 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 Knud Jessen

In research: Knud Jessen 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 Knud Jessen 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: Knud Jessen is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1884 births, 1971 deaths, 20th-century Danish botanists, so understanding it makes those chapters shorter.
In everyday life: Look for Knud Jessen 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 Knud Jessen in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Knud Jessen 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 Knud Jessen out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Knud Jessen in simple terms?

Knud Jessen (29 November 1884 – 14 April 1971) was a Danish botanist and quaternary geologist. Biography Jessen was born at Frederiksberg, Denmark.

Why does Knud Jessen 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 Knud Jessen?

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 Knud Jessen.