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ONE afternoon in 2016, 快猫短视频 consultant Stuart Clark and I barricaded ourselves in a room, armed with flip charts and pens, in a bid to work out what fundamental physics looked like. This turned out to be a confusion of lines and arrows 鈥� dotted, looping, scribbled out, realigned 鈥� between boxes adorned with 鈥淓 = mc²鈥�, 鈥渦ncertainty principle (?)鈥�, 鈥渜uantum field theory鈥� and 鈥渃osmic inflation!鈥�.

The finished product was more coherent. We were proud of it when it appeared in 快猫短视频 鈥� even if we had somehow forgotten about thermodynamics. We could have done with the clear mind of a Jim Al-Khalili. Loyalty doesn鈥檛 allow me to admit he has made a better job of what we attempted, but his new book is really rather good.

Al-Khalili, a nuclear physicist at the University of Surrey, UK, is well known for BBC Radio 4鈥檚 The Life Scientific, in which he interviews leading scientists.

He describes The World According to Physics as an 鈥渙de to physics鈥�, the subject he fell in love with as a teenager. Like Carlo Rovelli鈥檚 bestseller Seven Brief Lessons on Physics, it is short. But in extending Rovelli鈥檚 96 pages to 300-odd, he offers a thorough overview of what physics says about reality and the problems created in so doing.

It is an interesting time for such a survey. The early 20th-century innovations of 贰颈苍蝉迟别颈苍鈥檚 relativity and quantum mechanics, and experimental and observational advances on scales from the very small to the vast expanse of the cosmos, more or less overturned everything we thought we knew.

These innovations allowed the development of two 鈥渟tandard models鈥� 鈥� of particle physics and of cosmology 鈥� that, with the laws of thermodynamics, could be seen as telling us all we need to know. Yet as Al-Khalili observes, we are further away from the end of physics than we thought 30 years ago.

鈥淎l-Khalili鈥檚 easy turn of phrase and feel for metaphor give a sense of physics as a box of delights and woes鈥�

In part, that is because relativity and quantum mechanics provide us with very different, contradictory, pictures of such fundamentals as space and time. In 贰颈苍蝉迟别颈苍鈥檚 picture, these meld into one smooth fabric, space-time; in quantum theory, they remain strangely apart.

Once again, that is to ignore thermodynamics, which provides a third picture of the flowing time we experience, caused, as Al-Khalili tells it, by the increase of 鈥渦seless energy鈥�, or entropy. Some argue this connection isn鈥檛 so cut and dried. And to square our standard model of cosmology with observations of the universe, we had to invent dark matter and dark energy, which together make up 95 per cent of all stuff but which quantum theory (the directing theory of 鈥渟tuff鈥�) can鈥檛 explain. Lots still to do, then.

Al-Khalili鈥檚 easy turn of phrase and feel for metaphor give us a sense of fundamental physics as a box of delights and woes. His true metier is quantum physics, where he is admirably lucid and even-handed in dealing with the various interpretations that seek to explain its picture of a 鈥渇uzzy鈥� reality so at odds with our lived experience.

Here mystery builds on mystery, culminating in a split. Some say we shouldn鈥檛 concern ourselves with the workings of the quantum world, because the picture the theory delivers squares with experiments and allows useful technologies to be built on top of it. Others believe physics should describe the world, and tell us why things are as they are. Al-Khalili is one such, but because he doesn鈥檛 have a pet theory, he can argue both for fundamental physics and for the scientific method 鈥� less for offering enlightenment as a destination than for a thrilling journey.

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