You may have wondered recently if you are living in a particularly mad type of parallel universe, given the surreal nature of world events. If so, help is at hand. Jim Al-Khalili¡¯s latest book, The World According to Physics, may not explain Brexit, politics or the climate emergency, but it does tackle the nature of reality. With a sunny briskness it focuses on the real issues: What is the universe made of? How do we understand it? How do physicists think ¨C and can you trust them (spoiler alert: yes, you can)? It is a self-proclaimed ¡°ode to physics¡± that tours the extremes of space ¨C from the widest stretches of the universe to the smallest fundamental particles and most short-lived processes, with diversions into complexity and the arrow of time for good measure. If you¡¯ve ever wondered how any of the universe works, then this book could be for you.

Al-Khalili eases us in by describing the vast range of scales and timescales that physics ¡°so brazenly addresses¡±, before turning to the three pillars of modern physics whose discussion forms the bulk of the book. We learn about Einstein¡¯s theories of relativity and how this describes the largest scales of the universe (¡°This is not something you will be taught at school!¡±); quantum mechanics, which describes the smallest scales (¡°the most mind boggling and frustrating scientific theory ever devised¡±); and thermodynamics, which describes complex systems (¡°a matter of statistical inevitability¡±). Your intuition may suffer a little collateral damage along the way. Al-Khalili warns ¡°you may be shocked¡± by learning how physics connects space and time, and that ¡°our grip on what is real becomes increasingly tenuous¡± in the quantum world. He does not exaggerate.

Despite their shocking strangeness, these theories are incredibly successful, but that¡¯s not enough for reductionist physicists. Three different approaches to understanding the universe are at least two too many to be comfortable with, so we learn too of the latest attempts to unify them into one deeper, more fundamental theory. If you thought that conquering the physical universe was enough for one book, then be ready for a pleasant surprise. By the end of the book Al-Khalili even mulls the possibility that quantum mechanics could play a role in evolutionary biology, since ¡°it¡¯s just...well¡­physics¡±.

Throughout the story, Al-Khalili keeps us at the frontiers of research ¨C discussing the current status of dark energy, quantum computing, interpretations of quantum theory, string theory and quantum gravity (and much else besides). The downside of covering so much in so short a text is that descriptions are necessarily not very detailed and some interesting state-of-the-art research is little more than mentioned. However, there¡¯s more than enough information to give you an idea to match the words you may have come across, and the book includes a very good list of further reading should you want to know more about any topic.

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If you¡¯re worried about the brain-expanding implications of reading about the frontiers of science, don¡¯t be. No prior knowledge is required, only curiosity and an ability to suspend disbelief in the more non-intuitive aspects of the universe. Physics is reassuringly unrolled at the level of a particularly intense fireside chat and Al-Khalili is an expert storyteller. If you¡¯ve ever watched his television programmes, you may even hear his voice inside your head holding a private one-way conversation about all things physical, since the book¡¯s tone and style of explanation are similar.

If you are already familiar with the area, you may not find deeper insight here, but you will come across ideas and theories that you want to know more about. Above all, you will admire Al-Khalili¡¯s enthusiastic yet scientifically correct descriptions and fondness for good nerdy analogies, which are almost as brain-bending as the phenomena they illustrate. Who knew, for example, that ¡°you can fit more atoms into a single glass of water than there are glasses of water in all the oceans of the world¡±?

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Al-Khalili is never dull company, although sometimes he presents a situation so dramatically that you are convinced of impending physics disaster before you reach the conclusion. We read of ¡°a growing frustration in astrophysics¡± that dark matter is not yet understood, but by the next paragraph ¡°physicists looking for dark matter remain optimistic¡±. There is further ¡°mounting frustration¡± in a section mulling potential crises in physics and the fact that the Large Hadron Collider has not produced anything else as noteworthy as the Higgs boson (yet). Al-Khalili frets that the longer that evidence to confirm supersymmetry theory takes to materialise, ¡°the more frustrated we become¡±. However, we don¡¯t have to wait long for his natural optimism to bounce back with ways in which theoretical physics has forged ahead and opened up a wealth of possibilities for future scientific progress.

Despite the title, this book is not just about science. It also contains a very personal account of what makes physics special and what it is like to be a physicist. What might surprise you is the sense of physics as a vocation, to the extent that physics is stamped through the author like a stick of rock. Al-Khalili comes across as something of a physics Jedi wielding a lightsaber of scientific truth at every opportunity. Not content to view a theory as a mere toolbox (¡°every fibre of my being tells me this should not be enough for a physicist¡±), he imbues physics with aesthetic and philosophical value (¡°the true beauty of physics, for me, is¡­in the deep underlying principles that govern the way the world is¡± ¨C a beauty ¡°no less awe-inspiring than a breathtaking sunset¡±). In Al-Khalili¡¯s eyes, physics can never be just a job because the urge for understanding that underlies it is so fundamental to human nature. These sentiments make the book something of an ode to being a physicist too.

Throughout the text, Al-Khalili has enjoyed being ¡°(just a little) polemical here and there¡±, and the book could easily be titled ¡°The World According to Jim¡±. He examines conspiracy theories, untestable theories, balance in the media and the importance of science (¡°scientific progress is inexorable, which, by the way, is always a good thing¡±). While on the subject, he asserts that scientific progress demands an ¡°unwavering commitment¡± by scientists to honesty and doubt. To exemplify the point, he tells a story of finding a mistake in a calculation he made for a documentary. Most people might be tempted to quietly reshoot a correct explanation and hope that no one ever finds out ¨C but not our author. Instead, he recognises that the situation presents a golden opportunity to demonstrate the scientific method (¡°making mistakes is normally the way science progresses¡±) and shoots new scenes explaining his mistake with full and unabashed disclosure.

It is this insight into physicists and the particular way they regard the universe, combined with a winning description of the physics itself, that make the book unique. Al-Khalili is determined to make you see why physics is ¡°so wonderful¡±. His enthusiasm and zeal will ensure that you cannot fail to be impressed and entertained.

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Tara Shears is professor of physics at the University of Liverpool.

The World According to Physics
By Jim Al-Khalili
Princeton University Press, 336pp, ?12.99
ISBN 9780691182308
Published 10 March 2020

The author

Jim Al-Khalili, professor of physics and of public engagement in science at the?University of Surrey,?was born in Baghdad in 1962 and had what he once described to ³ÉÈËVRÊÓƵ as ¡°a very happy childhood¡±. Yet just two weeks after Saddam Hussein came to power in 1979, the family decided to move to the UK ¨C a decision, he reflected, they had taken ¡°just in time; a few months later and I would have been conscripted for the Iraq-Iran war and unlikely to be alive today¡±.

After studying physics at Surrey, Al-Khalili stayed on for a DPhil on nuclear reaction theory and has spent most of his career there, apart from a brief interlude as a postdoctoral fellow at?University College London. Along with a number of publications devoted to making his field accessible to non-specialists, he drew on his bilingual upbringing to write Pathfinders: The Golden Age of Arabic Science (2010).

This book was based on a three-part BBC television series, Science and Islam (2009), something reflecting Al-Khalili¡¯s deep commitment to bringing science to a wider audience. Back in the mid-1990s, when ¡°halfway through [a] second postdoctoral fellowship¡±, he once recalled, he began to ¡°feel the pull towards getting involved in communicating science¡±. By trying to find ways to ¡°get across how the scientific method works¡±, he hoped to help?develop the kind of ¡°scientifically literate society¡± we urgently need today.
Although he was clearly told to ¡°leave [such outreach] to others who weren¡¯t as research-active as me¡±, al-Khalili ignored this advice and has now presented programmes on topics ranging from the Big Bang, electricity and Einstein¡¯s brain to The Science of Dr Who.?He has also, for many years, presented the BBC Radio 4 series, The Life Scientific.

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Matthew Reisz