physics

William A. Jeffrey

William A. Jeffrey 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 William A. Jeffrey rather than just read about it. In short: William A. Jeffrey is an American astronomer and astrophysicist.

Key takeaways

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

Reference excerpt

William A. Jeffrey is an American astronomer and astrophysicist. He was the CEO of SRI International from 2014 to 2021 and the 13th director of the National Institute of Standards and Technology from 2005 to 2007.

Education He earned a bachelor of science in physics from the Massachusetts Institute of Technology and a Ph.D. in astronomy from Harvard University.

Early career Jeffrey was the deputy director for the Advanced Technology Office and chief scientist for the Tactical Technology Office with the Defense Advanced Research Projects Agency (DARPA). He was involved in federal science and technology programs from 1988 to 2008. He served as senior director for homeland and national security and the assistant director for space and aeronautics at the Office of Science and Technology Policy (OSTP) within the Executive Office of the President. At OSTP he was instrumental in guiding the creation and development of the science and technology aspects of the newly created Department of Homeland Security especially as they relate to weapons of mass destruction countermeasures. He also served as the assistant deputy for technology at the Defense Airborne Reconnaissance Office, where he supervised sensor development for the RQ-1 Predator and RQ-4 Global Hawk Unmanned Aerial Vehicles (UAVs) and the development of common standards that allow for cross-service and cross-agency transfer of imagery and intelligence products. He also spent several years working at the Institute for Defense Analyses performing technical analyses in support of the Department of Defense.

Later career He was the 13th director of the National Institute of Standards and Technology (NIST), sworn into the office on July 26, 2005. He was nominated by President Bush on May 25, 2005, and confirmed by the U.S. Senate on July 22, 2005. In his capacity as NIST Director, he was a member of the Election Assistance Commission's Technical Guidelines Development Committee, tasked with assisting the EAC in drafting the Voluntary Voting System Guidelines. Jeffrey resigned as NIST Director in September, 2007, to assume the post of director of the Science and Technology Division, Studies and Analyses Center, Institute for Defense Analyses. Jeffrey was the president and CEO of HRL Laboratories, LLC from September 2008. He became the president and CEO of SRI International in September 2014, succeeding Curtis Carlson. He was succeeded by David Parekh in October 2021.

Awards and memberships In 2008, he received the Navigator Award from the Potomac Institute for Policy Studies. He was awarded the Secretary of Defense Medal for Outstanding Public Service. Jeffrey is a member of the Board of Directors of TE Connectivity, a fellow of the American Physical Society, and an honorary member of the International Society of Automation. In 2026 he joined the board of directors of the California Council on Science and Technology.

References

Illustrations

Worked examples

Example 1 — a first encounter with William A. Jeffrey

Start with the simplest possible case. Write down what William A. Jeffrey 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 William A. Jeffrey 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 William A. Jeffrey 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 William A. Jeffrey

In research: William A. Jeffrey 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 William A. Jeffrey 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: William A. Jeffrey is common in secondary-school and first-year university syllabi. It links to neighbouring topics 21st-century American physicists, Election technology people, Fellows of the American Physical Society, so understanding it makes those chapters shorter.
In everyday life: Look for William A. Jeffrey 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 William A. Jeffrey in 20 minutes

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

Frequently asked questions

What is William A. Jeffrey in simple terms?

William A. Jeffrey is an American astronomer and astrophysicist.

Why does William A. Jeffrey 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 William A. Jeffrey?

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 William A. Jeffrey.