experience slower ageing in both brain and body than those who slept either more or less. Sleep trackers promise to help people hit this sweet spot. Apps typically record movement and sound, sometimes inferring breathing rates from the audio. Smartwatches record movement and use photoplethysmography— measuring blood flow by shining low-intensity light onto the skin and detecting how much reflects back. This is used to estimate heart and breathing rates. Rings often measure skin temperature, too. Most trackers are very good at distinguishing sleep from being awake. Several studies have compared them to polysomnography, which uses electrodes to record eye movements, brain activity, muscle tone and heart rate, and is the gold standard for measuring sleep. One paper, published in Sensors, a specialist journal, in 2024, tested three popular wearable trackers and found that all agreed with polysomnography around 95% of the time in telling sleep from wakefulness across the night. When it comes to identifying the different sleep stages, trackers are less accurate. A good night requires cycling between rapid-eye movement (REM) sleep, in which dreams are had, and several stages of non-REM sleep ranging from light to deep. Wearables agree with polysomnography on sleep-stage classification only around 50-80% of the time. That merits a C+ to B+, says Rebecca Robbins, a sleep scientist at Harvard Medical School, who was involved in one of the studies. Not great—yet many devices include these metrics in their calculation of sleep scores. Despite trackers’ shortcomings, most sleep researchers and therapists view them positively. Dr Robbins says they give people a better, more objective sense of how long they slept (and may reveal they are in fact getting plenty of winks). Plus, they do seem to improve sleep habits. In a survey by the American Academy of Sleep Medicine 55% of adults who reported using sleep trackers said they had changed their behaviour after learning from the data. One small study, published in the Journal of Clinical Sleep Medicine in 2020, found that wearing a sleep tracker for a week improved self-reported sleep quality.
Too much data can have downsides, though. Unlike trying to eat healthily or exercise, putting more thought and effort into sleeping can backfire. As many as 30% of those who track their sleep report feeling anxious about the data they collect, a phenomenon researchers called orthosomnia. Concern about poor sleep is one of the most common causes of a sleepless night; only financial worries keep people up more often. But sleep data is not worth losing sleep over, because there is an alternative to sleep tracking: whether you wake up feeling rested is the best indicator of how good your night was. ■ After a free, evidence-based guide to health and wellness? Sign up to our weekly Well Informed newsletter. This article was downloaded by zlibrary from https://www.economist.com//science-and-technology/2026/05/29/should-you-use-a- sleep-tracker
How many times a day do you think about Alexander the Great? The hidden tastemakers of the literary world Why you should never skip a TV intro The best, and worst, TV series and films of 2026 (so far) Travel is becoming a competitive sport
How many times a day do you think about Alexander the Great? A new book is as riveting as its protagonist was June 4th 2026 How do you measure the greatness of Alexander the Great? Perhaps by the size of the empire he conquered (it stretched 4,800 kilometres, from Athens to India). Or the speed with which he conquered it (about a decade). Or the cities he founded (between six and 17, many called “Alexandria”). Though, as a new book by Edmund Richardson, a professor of classics and ancient history at Durham University, shows, there are darker measures of this man. He has been called “mad”, “Alexander the not-so-great” and “one of the greatest killers the world had ever known”. This is with reason: some have estimated that almost 1% of the ancient world’s population died as a result of his campaigns.
That has not stopped the adulation. If men think of the Roman Empire many times a day, historians seem to think of Alexander almost as often. He obsesses people: feature films glamorise him; documentaries follow in his footsteps; almost 5,000 books have dissected him. His acolytes have ranged from Julius Caesar to Napoleon to modern business gurus. Like all history, these texts reflect their time. Machiavelli admired Alexander’s manly leadership style (he killed his enemies). Modern texts take a more managerial approach: a professor at INSEAD, a business school, wrote an article titled “Eleven Leadership Lessons from Alexander the Great”. This included advice to “Consolidate Gains” and “Invest in Talent Management”. And, you might add, “Avoid Killing 1% of the Known World”. (Tech bros and politicians, take note.) Ancient statistics are iffy. But this book—a rip-roaring cradle-to-(drunken)- grave look at Alexander—offers other statistics, too. In its pages there are 11 instances of various body parts being severed (mostly heads, but sometimes limbs and penises); the word “murder” appears 38 times, and “kill” pops up around 100 times. It is brutal, violent and staggeringly bloody. It is, in other words, splendid fun. It is also, in some ways, unusual. Everyone knows that history (the thing with battles) is divided into eras: the classical, the medieval, the modern. But history (the thing with books) is divided into eras, too. The past century alone has seen vogues for Marxist history, feminist history and—most recently—hand-wringing history. In recent years, people have fretted over the sins of everyone from Mahatma Gandhi to that notorious villain Jane Austen. Classics, which has been accused of being “part of the scaffold of white supremacy”, has been particularly apologetic, and has hurried to correct its “bias”. One recent book on Alexander declared it was less interested in the man than in those who “suffered under his rule”. It is doubtless very virtuous. What it is not is very interesting. Mr Richardson’s “Alexander the Great”, by contrast, does not hand-wring. It rollicks. It rollicks through his childhood (he tames an untameable horse); it rollicks through his early battles (he conquers an unconquerable city); it
rollicks through his myth-making (he undoes the undoable “Gordian knot”). It rollicks, of course, through his frolicking. Alexander’s lovers included his friend Hephaestion, “360 of Darius’s former concubines (one for each day of the Persian year) and a spectacularly handsome young Persian named Bagoas”. Where there is a good story to tell, Mr Richardson does not deconstruct or critique it. He tells it, with gusto. Take the siege of Tyre. When Alexander started to attack this city, he was not yet the “Great”—merely a slight, shortish, almost-boy with blond, curling hair, grown long in imitation of his hero, Achilles. The island-city of Tyre was magnificent. The stinking purple dye of its seashells made the clothes of the Mediterranean purple—and had made Tyre stinking rich. The city, in modern-day Lebanon, stood nearly a kilometre out to sea above looming walls and patrolling guards of warships. It was assumed it was unconquerable. You can see where this is going. One man-made causeway, seven months and 2,000 crucified Tyrians later, and the siege was over. Though much like Alexander himself, this history does not hang about: it is up and off to India and, eventually, his agonising death in Babylon. Early slurs said he was killed by alcohol poisoning; Mr Richardson thinks drinking water and typhoid are more likely. Its walk-on cast is starry and includes the philosopher Aristotle, his tutor, who gave Alexander an annotated copy of “The Iliad” and a love of literature (he slept with his copy). The detail here is delicious: you learn how to foil an enemy digging a tunnel into your city (pop in a pack of bears and a swarm of bees) and whether it is a good idea to herd cats into battle (as the idiom implies, it is not). This book has been described by its publisher as a “revelatory retelling”. But one of the newest and most interesting things about it is just that: it is interesting. For far too long history books have not tried hard enough to rivet readers. This is not a recent complaint. As Catherine Morland, the heroine of Austen’s “Northanger Abbey”, observed, it is odd that history “should be so dull, for a great deal of it must be invention”. One of the things people never seem to learn from history is how to write history well. In 1946 Samuel Eliot Morison, an American historian, accused
historians of producing “dull, solid, valuable monographs that nobody reads outside the profession”. In 2010 Gordon Wood, a professor, said that history writing was “in a crisis”, as academics write reams but have “very few” readers. This is partly, as a Marxist historian might say, explained by societal change: people are reading less of everything. Partly, too, they are consuming history in other ways: “The Rest is History” is one of the world’s most popular podcasts. But another explanation is just that so much academic history is almost aggressively badly written. Recent academic treatises on Alexander are rich in words like “deconstruct”—but low on the rip-roaring. Some of this is necessary: history advances through analysis, not anecdote. However, though analysis is essential, being dull is not. Tom Holland, one of the hosts of “The Rest is History”, says the “problem is those who can’t kick an addiction to jargon”. Too many “mistake writing stuff that is bloody hard to understand for being profound”, agrees Harry Sidebottom, a classics lecturer at Oxford. This book, which combines analysis with good old-fashioned fun, offers a lesson in how history can be both academically ambitious and readable. And why writers should talk a lot about the bears and the bees. ■ For more on the latest books, films, TV shows, albums and controversies, sign up to Plot Twist, our weekly subscriber-only newsletter This article was downloaded by zlibrary from https://www.economist.com//culture/2026/06/04/how-many-times-a-day-do-you-think- about-alexander-the-great