astronomy

John Ellenby

John Ellenby 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 John Ellenby rather than just read about it. In short: John Ellenby (9 January 1941 – 17 August 2016) was a British businessman. He was the founder of Grid Systems Corporation, maker of the Grid Compass, one of the first commercially successful laptop computers.

Key takeaways

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

Reference excerpt

John Ellenby (9 January 1941 – 17 August 2016) was a British businessman. He was the founder of Grid Systems Corporation, maker of the Grid Compass, one of the first commercially successful laptop computers. He also co-founded GeoVector, an early augmented reality company.

Biography Ellenby was born in Corbridge, in Northumberland, England. His father Conrad Ellenby was a nematologist. He studied geography and economics at University College London, and first encountered mainframe computers for the first time in the early 1960s, when he spent a year at the London School of Economics. He worked for the British firm Ferranti, where he worked on minicomputers. Ellenby moved to California in the 1970s, where he worked for Xerox, and became involved in the management of the development of the Alto and Alto II desktop computers. In 1978, Ellenby and Tim Mott proposed an idea to commercialise the Alto computer, but this idea was later abandoned due to financial constraints. Ellenby said that they "had to sandbag the Alto because with it we couldn't make their numbers and therefore wouldn't get any bonuses". In 1979, he cofounded Grid Systems Corporation with colleagues from Xerox PARC; the business started with $13 million of funding from Wall Street venture capitalists. In 1982, Grid built the Grid Compass, which was one of the first laptop computers to feature the now-popular clamshell design, and was used on the Space Shuttle Challenger in 1986. In 1988, Grid was sold to the Tandy Corporation. The design for The Compass computer was allegedly based on the shape of Ellenby's briefcase. In 1987, Ellenby founded Agilis Corporation; he acted as the President of the company until 1990, and in 1989 the company produced hand-held computers with built-in Ethernet ports. Ellenby also founded Geovector, a company based on applications of augmented reality. Ellenby died on 17 August 2016 in San Francisco.

References

External links In memory of John Ellenby [1]

Worked examples

Example 1 — a first encounter with John Ellenby

Start with the simplest possible case. Write down what John Ellenby 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 John Ellenby 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 John Ellenby 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 John Ellenby

In research: John Ellenby 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 John Ellenby 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: John Ellenby is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1941 births, 2016 deaths, Alumni of University College London, so understanding it makes those chapters shorter.
In everyday life: Look for John Ellenby 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 John Ellenby in 20 minutes

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

Frequently asked questions

What is John Ellenby in simple terms?

Why does John Ellenby 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 John Ellenby?

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 John Ellenby.