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The Janus Point

A New Theory of Time

Julian Barbour



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Bodley Head
05 November 2020
ABBEY'S BOOKSELLER PICK -----  Julian Barbour's 1999 book The End of Time was an arresting and somewhat mind-bending look at what I've come to regard as being the nub of our quest to understand the universe. Time. If we can figure out what time actually is, we will probably have found the key to the whole shebang. So I was enormously interested when this new book from Barbour appeared. Readers familiar with popular science writings around cosmology and the quantum from the likes of Paul Davies, John D Barrow, John Gribbin, Lee Smolin, Roger Penrose, Brian Greene, Brian Cox will find this an equally enlivening read as they continue on their own journey of discovery. Craig Kirchner


A ground-breaking challenge to our understanding of the universe and a brilliant solution with radical implications for our understanding of the nature of time itself.

What is time? Why is the past so different from the present and the future?

This simple question is in fact one of the deepest, most long-standing problems in physics. None of the known laws of the universe can fully explain it. In The Janus Point, Julian Barbour presents a bold new thesis and a possible solution, with radical implications for our understanding of the Big Bang and the nature of time itself.

His argument rests on two vital insights. The first is that the most common explanation for time - entropy - is flawed- firstly, because we have no way of explaining how the concentration of energy that would allow the Big Bang to take place came about, and secondly because none of our understanding of entropy takes into account the fact that the universe is infinitely expanding. In addition, our universe is actually becoming ever more complex and ordered as it expands, not less so. The second is a phenomenon which Barbour labels 'The Janus Point'- any system of particles in motion will pass through a single moment of smallest size, never to be repeated.

Combining these two observations, Barbour argues that the universe, and therefore time itself, may not have begun at the Big Bang, but rather at The Janus Point, thus solving the conundrum of entropy.

Monumental in vision and scope, The Janus Point offers a ground-breaking challenge to our understanding of the universe and a brilliant solution of breath-taking elegance and import to this most fundamental of problems.
By:   Julian Barbour
Imprint:   Bodley Head
Country of Publication:   United Kingdom
Dimensions:   Height: 234mm,  Width: 153mm,  Spine: 31mm
Weight:   605g
ISBN:   9781847924735
ISBN 10:   1847924735
Pages:   344
Publication Date:   05 November 2020
Audience:   College/higher education ,  Professional and scholarly ,  General/trade ,  Primary ,  Undergraduate
Format:   Paperback
Publisher's Status:   Active

Julian Barbour has been a Visiting Professor in Physics at the University of Oxford since 2008. He is the author of two books, The Discovery of Dynamics (Oxford University Press, 2000) and The End of Time (Weidenfeld and Nicolson, 1999). He is featured on national radio and TV, including BBC documentaries, regularly. He has appeared along with Stephen Hawking and Roger Penrose in the widely acclaimed Reality on the Rocks on Channel 4 in the UK.

Reviews for The Janus Point: A New Theory of Time

Julian Barbour has no peer when it comes to explaining scientific ideas in a way that is accessible without being simplistic -- Neal Stephenson, author of Snow Crash The origin of the arrow of time is arguably the most important conceptual problem in cosmology, and the prospect that it can be solved in a universe where time flows backward in the far past is as exciting as it is provocative. In this engaging book, Julian Barbour conveys this excitement admirably -- Sean Carroll, author of From Eternity to Here With a rare humanity and a perspective based on a lifetime of study, Barbour writes a book that is both a work of literature and a masterpiece of scientific thought -- Lee Smolin, author of The Trouble with Physics Julian Barbour is a profound and original thinker with the boldness to tackle some of nature's deepest problems. He is also a fine writer, and this renders his book - despite its conceptual depth - accessible to anyone who has pondered the mysteries of space and time -- Martin Rees, Astronomer Royal and former President of the Royal Society The Janus Point shows history-in-the-making: a project to recast the foundations of all of cosmology, gravity, thermodynamics and the arrow of time. The book has given me a lot to ponder. As Gauss said of Riemann's habilitation lecture, '[it] exceeded my expectations' -- Bill Unruh, Professor of Physics at University of British Columbia

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