The Hidden Reality


Brian Greene ( and has a gift for elucidating big ideas and knowing that a bombardment of too many small ones might make the armchair physicist despair.


‘The art of theoretical physics lies in simplifying the complex so as to preserve essential physical features while making the theoretical analysis tractable,’ he writes in his latest mind-bender, ‘The Hidden Reality.’ To put that in even more user-friendly fashion, Greene values ‘the art of knowing what to ignore.’ He says this at the very the start of the new book. And it is a necessary reassurance, especially when he offers a preliminary idea of what subjects he will be taking on. The book explores the idea of parallel universes, the array of different forms they might take, the strangeness of their implications (‘this would blow Newton’s mind’), the wild extremes that can be extrapolated from such conjectures and the challenge of backing up theory with scientific proof. Yet the first page promises that it will take ‘no expertise in physics or mathematics on the part of the reader’  to keep up.


Greene lays more groundwork for the readability of The Hidden Reality when he puts certain groundbreaking, now basic ideas in their proper perspective. In 1919, when astronomical observations validated Einstein’s 1915 predictions about planetary motion, The New York Times ran an article with the headline “Lights All Askew in the Heavens, Men of Science More or Less Agog.” Today nobody’s agog — and you’re apt to be walking around with a hand-held device that has a GPS, the accuracy of which can be traced to Einstein. Perhaps future generations will similarly take in stride the thought of parallel universes — and not just the kinds that are a mainstay of comic books and science fiction.


The Hidden Reality starts by raising the question of whether space is infinite or finite. Then it looks at the cosmological principle (the assumed homogeneity of the cosmos) and that principle’s implications for how a multiverse ( might be configured. A little further on in this same early chapter Greene imagines a woman who has many shoes. Calling her Imelda, he uses her wardrobe permutations to make a more abstract point: ‘an infinite number of appearances with a finite number of outfits ensures infinite repetition.’ This chapter is called ‘Endless Doppelgängers.’ It builds upon the idea that infinite variations of ourselves, our lives and our solar system are within the theorist’s realm of possibility. Greene then moves to ‘Eternity and Infinity,’ and soon he is introducing both inflationary cosmology, which is one thing, and the inflaton field, which is quite another. Then he sets forth colossal numbers that are ‘so extreme that they defy analogy.’ But he offers an analogy anyway, and it’s the kind that make his book so startling – ‘They imply that a region of space the size of a pea would be stretched larger than the observable universe in a time interval so short that the blink of an eye would overestimate it by a factor larger than a million billion billion billion.’


By now, the 11-dimension string theory models of his earlier books (to which Greene helpfully steers the reader for background material) are looking downright commonsensical. The Hidden Reality moves on to increasingly speculative and exotic discussions of a bubble multiverse (‘Think of the universe as a gigantic block of Swiss cheese….’) a holographic one, a brane-world scenario (courtesy of string theory), computer-driven simulations, questions of how probability relates to infinity, and the Many Worlds view of quantum mechanics.


There is no disguising that this is difficult subject material, but it is the closest any of us non specialists are going to get to the wild frontiers of modern cosmology. There are many beautiful (albeit eye-glazing) passages and many crystal clear thoughts. For these reasons I encourage you to take a deep breath and read The Hidden Reality.


To hear Brian Greene listen to the BBC Radio 4 ‘In Our Time’ episode (45 minutes) on ‘theories of everything’. Available from the link  Greene is joined by John Barrow, Professor of Mathematical Sciences at the University of Cambridge and author of The Constants of Nature; Dr Val Gibson, particle physicist from the Cavendish Laboratory and Fellow of Trinity College, Cambridge. Chaired by Melvyn Bragg. First broadcast Thursday 25 Mar 2004.


Also don’t miss Greene’s book ‘The Fabric of the Cosmos’ (2004) Enquire at your local library or available at


384 pages in Penguin paperback edition

ISBN 978-0141029818



Brian Greene

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