physics

Per Bak

Per Bak is a physics 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 Per Bak rather than just read about it. In short: Per Bak (8 December 1948 – 16 October 2002) was a Danish theoretical physicist who coauthored the 1987 academic paper that coined the term "self-organized criticality." Life and work After receiving his Ph.D. from the Technical University of Denmark in 1974, Bak worked at Brookhaven National Laboratory. He specialized in phase transitions, such as those occurring when an insulator suddenly becomes a conductor or whe…

Key takeaways

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

Reference excerpt

Per Bak (8 December 1948 – 16 October 2002) was a Danish theoretical physicist who coauthored the 1987 academic paper that coined the term "self-organized criticality."

Life and work After receiving his Ph.D. from the Technical University of Denmark in 1974, Bak worked at Brookhaven National Laboratory. He specialized in phase transitions, such as those occurring when an insulator suddenly becomes a conductor or when water freezes. In 1987, he and two postdoctoral researchers, Chao Tang and Kurt Wiesenfeld, published an article in Physical Review Letters setting a new concept they called self-organized criticality. The first discovered example of a dynamical system displaying such self-organized criticality, the Bak-Tang-Wiesenfeld sandpile model, was named after them. This followed publication in 1986 in the Journal of Geophysical Research of a very similar model of earthquakes by Jonathan I. Katz of Washington University in St. Louis. Faced with many skeptics, Bak pursued the implications of his theory at a number of institutions, including the Brookhaven National Laboratory, the Santa Fe Institute, the Niels Bohr Institute in Copenhagen, and Imperial College London, where he became a professor in 2000. In 1996, he took his ideas to a broader audience with his ambitiously titled book, How Nature Works. In 2001, Bak learned that he had myelodysplastic syndrome and died from complications of a stem-cell transplant. Bak is survived by his second wife, Maya Paczuski, a fellow physicist and current professor at the University of Calgary, with whom he has coauthored papers, and his four children.

Selected publications Bak, P (1 June 1982). "Commensurate phases, incommensurate phases and the devil's staircase". Reports on Progress in Physics. 45 (6): 587–629. CiteSeerX 10.1.1.131.4735. doi:10.1088/0034-4885/45/6/001. {{cite journal}}: Cite uses deprecated parameter |citeseerx= (help) Bak, Per; Tang, Chao; Wiesenfeld, Kurt (27 July 1987). "Self-organized criticality: an explanation of 1/f noise". Physical Review Letters. 59 (4): 381–384. Bibcode:1987PhRvL..59..381B. doi:10.1103/PhysRevLett.59.381. PMID 10035754. 1996, How Nature Works: The Science of Self-Organized Criticality, New York: Copernicus. ISBN 0-387-94791-4 Bak, Per (December 1983). "Doing physics with microcomputers". Physics Today. 36 (12): 25–28. Bibcode:1983PhT....36l..25B. doi:10.1063/1.2915383.

References

References Jensen, Mogens Høgh (November 2002). "Per Bak (1947–2002)". Nature. 420 (6913): 284. doi:10.1038/420284a. PMID 12447430. S2CID 20688217.

Worked examples

Example 1 — a first encounter with Per Bak

Start with the simplest possible case. Write down what Per Bak claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, 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 Per Bak 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 Per Bak 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 Per Bak

In research: Per Bak appears in physics 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 Per Bak 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: Per Bak is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1948 births, 2002 deaths, 20th-century Danish physicists, so understanding it makes those chapters shorter.
In everyday life: Look for Per Bak 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 Per Bak in 20 minutes

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

Frequently asked questions

What is Per Bak in simple terms?

Per Bak (8 December 1948 – 16 October 2002) was a Danish theoretical physicist who coauthored the 1987 academic paper that coined the term "self-organized criticality." Life and work After receiving his Ph.D. from the Technical University of Denmark in 1974, Bak worked at Brookhaven National Labora…

Why does Per Bak matter?

Because it connects several physics 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 Per Bak?

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 Per Bak.