Jennifer Coopersmith was born in 1955 in Cape Town, South Africa. The family emigrated to England in 1958, travelling on the Union Castle line. They settled in London (for a while, Jennifer stayed with ‘Granny Belgium’ in Aywaille). She later attended Haberdashers’ Aske’s School in Acton, London, and obtained a BSc and a PhD in physics from King’s College, University of London.

Jennifer was a research associate at the University of British Columbia, working at the Tri-University Meson Facility (TRIUMF) during 1981-2. She finished her PhD in 1983, travelled in India and Nepal in the beginning of 1984, and subsequently worked as a computer programmer at Logica SDS in London, 1984-5 (on the award-winning project for HM Coastguards’ Search & Rescue).

There followed a period of part-time tutoring combined with motherhood (children born in 1986, 1989 and 1995), working at Kingston Polytechnic and Kingston College of Further education (during 1986-7) and then the Open University, 1987-96, teaching S102, S354 and S281 variously at Reading, London, Winchester and Oxford.

In 1997, Jennifer and family left Divinity Road, Oxford and moved to Bendigo, Australia, where they had a ‘hobby farm’ with a cat, dog, goat, hens and two Shetland ponies (by comparison with horses, the ponies made the estate look bigger), and many kangaroos. She taught part-time at La Trobe University in Bendigo and Swinburne University of Technology in Melbourne (marking assignments on ‘The Measurement of G’ and ‘Is there a cosmic asymmetry between matter and antimatter?’).

In 2010 Jennifer published “**Energy, the Subtle Concept: the discovery of Feynman’s blocks, from Leibniz to Einstein**”, Oxford University Press, and then the paperback edition came out in 2015. The book is a semi-popular account of how **Energy** came into physics. In 2017, she published her second book for the OUP, “**The Lazy Universe: an introduction to the Principle of Least Action**”. The book has more mathematics in it than her previous book – so it could be considered as semi-semi-popular. Hoping this trend (in reduced popularity) does not continue, Jennifer’s third book is currently under way. Meanwhile (2019), Jennifer and husband, Murray Peake, translated Lazare Carnot’s “**Essay on Machines in General**” from 18th-century French to English (with notes and commentary by Raffaele Pisano).

In 2015 Jennifer changed countries for the fifth time – she and her husband now live in France.

Jennifer Coopersmith you are amazing. I just finished reading, cover to cover, your book “The Lazy Universe”. It is simply awesome. I so wished you were there teaching me as a freshman in college. I am actually a chemist but my physics background was not great and I had to play catchup for years. Your simple and clear explanation of physics is extroardinary. Now I get it. Thanks.

Thank you for writing “The Lazy Universe!” I’ve been working through it and it’s been very helpful in laying out the derivation of Hamilton’s Principle (the Principle of Least Action), so I can see now why systems try to minimize the time-integral of the Lagrangian. I’ve also been through a few proofs of where the Euler-Lagrange equation comes from, how it can be applied to Hamilton’s Principle to obtain the equations of motion for various coordinates, and how the Euler-Lagrange equation is coordinate-invariant so that as long as we can express one set of coordinates as functions of some other set of coordinates (and possibly time), Lagrange’s equations of motion still hold.

The thing that’s tripping me up is that q(t) in the Euler-Lagrange equation doesn’t have to be a spatial coordinate, but can be just about anything (“changes in capacitance, surface tension, magnetic field, phase of a wave, strain in a beam, pressure within a fluid, and so on” on pg. 72). I’ve been through the example on damped resonant circuits you have in the appendix and can see that Lagrange’s equations of motion work when q(t) represents the charge in a wire (along with other examples in electrodynamics: Feynman shows how it can be used to get the Lorentz force equation and Poisson’s equation, for example), so I can see that it *does* work for q(t)’s other than spatial coordinates, but I don’t understand *why.* Is there a proof somewhere of why q(t) is allowed to be so many different physical quantities? How did it ever occur to someone to try to use Lagrange’s equations to solve for something other than a spatial coordinate?

Hi Charlie, thanks for your appreciation, and welcome to the slowly growing band of people who begin to realize that the Principle of Least Action underlies all physics. Happy to answer your questions (in brief) but please direct them to me at j.coopersmith@latrobe.edu.au