That secrecy ended last week. On May 14th the company published preprints of papers which it is submitting to peer-reviewed journals describing its particles in detail. Most of the company’s data, it turns out, concerns spheres less than a thousandth of a millimetre across and made entirely of amorphous silica (the same stuff that opals are made of) with a specially treated surface. A second, similarly sized version has a surface shell of amorphous silica but a core of calcium carbonate. In an interview at a meeting on geoengineering hosted by the Climate Systems Engineering initiative (CSEi) at the University of Chicago a few days after the preprints were uploaded, Yanai Yedvab, Stardust’s boss, stressed the degree to which the particles were part of an “end to end” approach to geoengineering technology which the company hoped to provide to any governments which might, eventually, decide that geoengineering is a good idea. The reception was decidedly mixed. Although the use of calcium carbonate and silica to these ends has been explored before, it has never been done in such depth. The lion’s share of research on stratospheric geoengineering assumes instead that the cooling would be done by mimicking the cooling effect of large volcanic eruptions: in other words, injecting a sulphur-rich chemical high into the atmosphere, where the sulphur ends up in tiny reflective droplets. There is a problem with this approach which has nothing to do with climate. Breathing in sulphate particles is bad for people. And particles high up in the stratosphere will inevitably drift down. The amount of sulphate that would be used would, admittedly, be small relative to the total quantities emitted by industry, and it would not be concentrated close to where people live. Nevertheless, when Dr Yedvab says “Dispersing millions of tonnes of toxic materials above the heads of their children for decades is something [people] wouldn’t feel that comfortable about,” it is hard to disagree. Amorphous silica is not in itself a health concern. But that does not mean that the Stardust particles will necessarily be safer than sulphates after a few years of weathering. On this and other matters—such as the idea that the particles could be chemically tagged—the scientists gathered in Chicago seemed unconvinced. “I think the work they’ve done on the particles is really terrific,” says David Keith, CSEi’s faculty director and a longtime
leader in geoengineering research. “What I don’t buy is that it’s definitely safer or definitely a good thing.” It might be tempting to see this as a reflexive resistance to incomers. But there is something deeper at play. Almost all geoengineering researchers, as well as the charities which fund a significant part of their work, say they do so disinterestedly, equally happy to discover good news or bad. (The Degrees Initiative, a British charity which funds such research and takes that stance, is chaired by a member of The Economist’s editorial staff.) Stardust, by contrast, is a commercial undertaking. If its technology is never used, its investors will lose out. That means it has a vested interest in geoengineering going ahead, and in perpetuating a dim view of sulphates. “It’s not that there’s anything fundamentally wrong with for-profit companies,” said Dakota Gruener, who runs Reflective, a philanthropically funded solar-geoengineering research outfit, in an onstage discussion with Dr Yedvab at the Chicago meeting. “But when you have investors who are saying what we bet upon is that this will be deployed, it makes it hard to have that same level of objectivity.” Objectivity tends to engender a sense of trust. So does transparency—a norm in the field that was challenged by Stardust’s long silence. It does not help the case for trust that its original funding came through Awz Ventures, a technology investor based in America, Canada and Israel that has various links to intelligence and security services. Awz also has an advisory board led by Stephen Harper, a former prime minister of Canada noted for his friendliness to the fossil-fuel industry. Perhaps more important than the source of its funds, though, is their quantity. In October 2025 the original investment of $15m through Awz was joined by a second round of investors bringing in $60m. (One of those investors was the venture-capital arm of Exor, a shareholder in The Economist’s parent company.) A survey of research funding published by SRM360, a non-profit which provides information about solar geoengineering, suggests that this makes Stardust easily the most generously funded research outfit in the field.
Solar geoengineering has long been controversial. Those studying it have nonetheless made real progress in understanding its potential, and its scope for misapplication. Stardust’s ideas may in the long run be seen as a fruitful contribution to that progress. In the short run, it may well add to the controversy. ■ Curious about the world? To enjoy our mind-expanding science coverage, sign up to Simply Science, our weekly subscriber-only newsletter. This article was downloaded by zlibrary from https://www.economist.com//science-and-technology/2026/05/21/could-microscopic- spheres-of-silica-help-cool-the-planet
Science & technology | Well Informed How well do anabolic steroids work? Very. But beware the side-effects May 21st 2026 MOST SPORTING bodies prohibit performance-enhancing drugs. The Enhanced Games revels in the possibilities they offer. The competition, which kicks off on May 24th, allows athletes to use all sorts of substances, provided they are licensed and that they are administered under a doctor’s supervision. Many athletes competing in the games have been cagey about their plans. But in April Mitchell Hooper, a Canadian who has twice won the World’s Strongest Man competition, revealed his in detail. Aside from Adderall, a stimulant, Mr Hooper’s “stack” consists of various anabolic-androgenic steroids (AAS), a class of compounds that are chemical cousins of testosterone, the chief male sex hormone.
That makes sense: AAS are some of the most potent performance-enhancing drugs known, especially for boosting strength and power. They will probably be doing most of the heavy lifting for every athlete at the games. And they are popular with non-athletes, too: one meta-analysis from 2014 estimated that 6% of men have used them at least once. But just how effective are they? In short, very—at least when it comes to packing on muscle. In a much-cited study done in 1996, for instance, young men given high-ish levels of testosterone and told to do no exercise saw a 19% improvement in their lower-body strength after ten weeks. That was about the same as participants given placebo drugs but who hit the weight room three times a week. Those who combined steroids with training saw a 38% increase. Several other randomised control trials conducted since then have reported similar results. Steroids also boost levels of oxygen-carrying red blood cells, which might help with endurance sports. Gym wisdom holds that they improve recovery too, allowing athletes to train harder—though that has yet to be rigorously proved in humans. What this means for sporting performance is harder to quantify. Since steroids are banned in most sports, controlled trials on elite athletes are usually a non-starter. But in 1997 Clinical Chemistry published a remarkable paper based on documents from the East German state-sponsored doping programme that began in the 1960s. One chart shows turinabol, a steroid taken orally, improving the shot-put distance of a female athlete by around 15% in just 11 weeks. All this extra power comes with side-effects. For one thing, taking high levels of steroids raises the risk of heart disease. Artificial AAS also suppress production of the natural sort, causing infertility and, in men, testicular shrinkage. Usually, the body will resume production when you stop taking the drugs—but sometimes it does not. Cosmetic side-effects are another worry. In men genetically predisposed to baldness, steroids will accelerate hair loss. And as testosterone is the chemical from which the body synthesises oestrogen, some AAS can lead to unnaturally high levels of that hormone—causing some men to grow breasts.
In women, steroids can enlarge the clitoris; encourage the growth of body hair and beards; and deepen the voice. Some of the doped East German athletes (most of whom took steroids unwittingly) suffered lifelong health complications, and in 2006 won payouts from the company that made the drugs. Steroids clearly work. But powerful drugs have powerful downsides—a lesson that competitors in the Enhanced Games would do well to bear in mind. ■ 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/2026/05/15/how-well-do-anabolic- steroids-work
A blind tasting revolutionised the wine world 50 years ago The unlikely inspiration for North Korea’s first dictator Why the sex in “Rivals” is more than mere titillation Not all Jews believed their future lay in Israel Beware the typo—and other lessons of literary history Gamified novels—known as LitRPG—are a winning format
A blind tasting revolutionised the wine world 50 years ago Just don’t mention the Judgment of Paris to the French May 21st 2026 “MAYDAY!” COMES from the French m’aider (help me). But no one in the stiff-lipped wine world expected a disaster on that sunny May day in 1976. The great names and noses of French wine had been invited by Steven Spurrier, an English wine merchant, to judge a blind tasting. Spurrier hoped to garner publicity for his shop and wine school in Paris. To mark America’s bicentennial, he had tracked down a few bottles from young, unknown producers in Napa Valley, California, and put them alongside celebrated ones from Bordeaux and Burgundy. Spurrier, like the judges, expected the French to easily win the taste-off. France was “the undisputed mistress of the vine”, according to the “World Atlas of Wine” (1971), which devoted 73 pages to it and just eight to California.