least theoretical evidence. But proponents claim that, in the dark dimension, string theory has made a testable prediction. And for a topic that has been stuck in the mud for half a century, that should be lauded. ■ This article was downloaded by zlibrary from https://www.economist.com/science-and-technology/2026/08/25/the-universe-is- peculiar-but-it-may-soon-become-less-so

Science & technology | Frozen fish How salmon evolved to cope with the ice age Their odd behaviour seems to be a relic of the time of the glaciers Aug 27th 2026 Some species thrived during the last ice age. Sabre-toothed cats, giant ground sloths, woolly mammoths and woolly rhinos all did pretty well. Others, however, were seriously inconvenienced—among them the chum salmon of north-western North America, which frequently found the rivers leading to and from their inland spawning grounds icebound. For those cut off in the sea, this was a nuisance. They had to make alternative arrangements, by seeking other, more accessible bodies of fresh water in which to lay their eggs. Those cut off on the land side, though, were stuck. And it was assumed until recently that because they were unable to complete the marine part of their life-cycle, they died out.

Not so, it turns out. A study published recently in Quaternary Research by Patrick Martin, an avid fisherman with a sideline as an amateur scientist, has employed genetics to show that some of the left-behinds not only endured, but thrived. Pacific chum salmon range around that ocean’s rim from Japan and the Koreas to the coast of Oregon. Naturally, there is genetic variation in such a widespread population. Some of this variation is, though, so extreme that it has left researchers baffled. Three particular hot spots are around Kodiak island and nearby Cook inlet, in Alaska, and in the Salish sea between British Columbia and Washington state. Intriguingly, it is not only the fishes’ genetics that differ, but also their behaviours. Most salmon migrate from the sea into fresh water to spawn in autumn or winter. The Salish sea population does so in summer. Similarly, salmon generally spawn in rivers. One of the Cook inlet populations, by contrast, does so in a lake. Isolation over periods of thousands of years is well understood to drive evolution. This is obvious on small islands, such as the Galápagos. But walls of ice can isolate, too. With this in mind, Mr Martin speculated that the Kodiak, Cook and Salish salmon are genetically different from their neighbours because they got trapped, and survived, in glacial lakes. Between 23,000 and 15,000 years ago glaciers created a lake on Kodiak island, with an area of 1,000 square kilometres and a depth of 300 metres. Glacial lakes also formed in valleys around the Olympic mountains of modern-day Washington state. To test his hunch, Mr Martin therefore convened a team of ichthyologists and geologists from the University of Washington and America’s National Oceanic and Atmospheric Administration to analyse the genes of 32,817 specimens from 310 populations around the Pacific rim. One question that needed an answer was whether the unusual genetics could be explained by a few salmon from Asia having taken a wrong turn and introduced their DNA into their North American cousins. The aberrant populations, however, bore no close relation to their Asian kin. Instead, the

team proposes that the ancestors of these survived the ice age isolated in freshwater lakes, where they went their own sweet evolutionary ways. During this period, Mr Martin and his colleagues argue, the fish rejigged their behaviour to treat the lakes they were trapped in like miniature oceans, complete with migrating up glacial streams feeding the lakes to spawn. That rejigging then persisted, at least in part, when the ice dams melted and the fish were liberated into the sea. At least some of chum salmon’s genetic peculiarities are thus, presumably, the drivers of their unusual behaviours. But others could be relics of physiological adaptations to the stress of a life confined to fresh water in a species that normally spends much of its existence in the briny. That is of interest to evolutionary biologists. It may also intrigue conservationists, for genetic diversity is a good insurance against extinction and these odd salmon populations have diversity in spades. And fish farmers may take notice as well, if they are thinking about trying to raise salmon in colder waters or even freshwater lakes, where sea lice are absent and infectious pathogens less common. ■ This article was downloaded by zlibrary from https://www.economist.com/science-and-technology/2026/08/26/how-salmon-evolved-to- cope-with-the-ice-age

Science & technology | The Louisiana purchase SpaceX plans to build the world’s biggest spaceport The $100bn facility aims to support up to 30 rocket launches a day Aug 27th 2026 SPACEX, ELON MUSK’S rockets-and-satellites firm, is already the planet’s leading space power. Last year it flew four times as much mass into orbit as every other company and country combined. But that is only the beginning of the firm’s ambition. On August 25th it confirmed rumours that have been swirling for months among space nerds by revealing the purchase of 50,000 hectares of southern Louisiana. In a joint announcement with the state’s government, it said it would spend $100bn building a gigantic rocket-launch facility on Pecan Island (part of which is pictured above), about 230km west of New Orleans.

Construction should start next year, with the first launches in 2029—though Mr Musk’s deadlines are famously optimistic. If and when the facility is finished, it will be by far the biggest rocket- launching complex in the world, with at least ten launch pads designed for SpaceX’s enormous Starship rocket, as well as propellant tanks, a deep- water port and an airport. Mr Musk’s ambition is for the site to host more than 30 rocket launches a day, to support both Starlink—the firm’s existing broadband-from-space service—and its plans to fly data centres into orbit, where they would benefit from both free solar power and an absence of NIMBYs. SpaceX currently launches Starship—which is still in testing—from its Starbase in Texas, and is building three new pads for it at Cape Canaveral in Florida. But Starbase is small, at around 140 hectares, and Florida is crowded: SpaceX shares the Cape with several other launch firms. The firm would have Pecan Island to itself. The location is attractive, as well. To maximise the solar power they can generate, the firm’s data centres will orbit over Earth’s poles. That means launching north or south rather than east or west. Regulators like launches to take place over the ocean, to minimise damage from accidents. From Louisiana, the only land overflown by a southward launch is a thin strip of central America. The new site is also reasonably close, by barge, to the giant rocket factory SpaceX is building in Texas. And the Louisiana coast is home to a great deal of oil and gas infrastructure, built to service drilling in the Gulf of Mexico. Starships burn methane, the chief constituent of natural gas, as fuel. With each launch using 1,300 tonnes of the stuff, being near to pipelines and storage tanks would be a big help. If Mr Musk hits his 30-launches-a-day target, his Louisiana purchase would allow SpaceX to fly about 2m tonnes of payload into orbit every year, up from about 3,800 tonnes in 2025. That really would put everyone else in the shade. ■ This article was downloaded by zlibrary from https://www.economist.com/science-and-technology/2026/08/26/spacex-plans-to-build- the-worlds-biggest-spaceport

Science & technology | The sky’s the limit Ukrainian military balloons may spoil Russia’s party Reports suggest some are being used to launch drones Aug 27th 2026 Balloons were applied to warfare in Europe shortly after their invention in France in 1783. (Chinese “sky lanterns” are far older, but are not known to have carried people.) They were used as observation posts and later, in the guise of tethered “aerostats”, as anti-aircraft devices. Latterly, China has employed them to spy on Taiwan, and Israel to keep an eye on Lebanon. America’s armed forces are taking an interest, too. But perhaps the most active practitioner is Ukraine. Ukraine has used balloons from the start of its war with Russia. In May it was reported that the country has launched over 1,000 of them into Russian territory since last autumn. They can drop bombs, distract air defences and

act as radio relays, passing commands to drones that would otherwise be out of range. Recently, Ukraine has tested a twist on this last approach by using balloons actually to carry drones, and thus extend the range of the drone strikes that are doing so much damage to Russian infrastructure. If winds are favourable, a balloon can both lift a drone partway to its target and, that done, launch it from altitude (up to 18km high), allowing it to glide yet further before it needs to switch on its engines. It looks as though Ukraine has been working on this taxi service for well over a year. In March 2025 a picture emerged of a drone dangling from an aerostat made by a Ukrainian firm. In September Russian Telegram accounts and officials reported that a large number of balloons had been spotted around the time of deep drone attacks. And this May Ukrainian soldiers reportedly employed a balloon to carry an American-made Hornet drone about 42km before releasing it at a height of 8km. Sources say the drone in question used up only 5% of its battery for electronic housekeeping during the balloon’s transit, leaving it almost fully charged for the mission. A ground-launched Hornet’s range is around 150km. Adding a balloon reportedly doubles that distance. At the moment, balloons are designed to carry only lighter drones, such as the Hornet, which are not fully autonomous. But if the drone-carrying balloon is fitted out as a relay, that will not matter. The Russians, too, are experimenting with balloons, but prevailing winds are against them. For Ukraine, the sky’s the limit. For Russia, it’s a blow. ■ This article was downloaded by zlibrary from https://www.economist.com/science-and-technology/2026/08/26/ukrainian-military- balloons-may-spoil-russias-party

Science & technology | Well Informed It now seems possible to vaccinate against cancer The latest results are promising, but not yet definitive Aug 27th 2026 First, pancreatic cancer. Now melanoma. A treatment for the former, announced in May, at the American Society of Clinical Oncology Annual Meeting, and which this column wrote about on June 12th, has been fast- tracked through America’s drug regulator and received approval on August 26th. Meanwhile, on August 19th, interim results of trials for a treatment for the latter—using mRNA technology developed for vaccination against infections—suggest that it is possible to vaccinate someone against their own cancer. In recent years an entire branch of medicine—immunotherapy—has been deployed to encourage the immune system to detect and destroy tumours.