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Dinosaur footprints measuring up to 1.25 metres long have been found deep inside a cave in France — on the roof. The tracks were made 166 million to 168 million years ago, when three dinosaurs traversed the shoreline of a sea. The site was then at the planet’s surface, but geological processes have buried and tilted the sediments, and the prints are now on the cave’s roof, 500 metres underground. Researchers say the footprints probably belong to an unknown species of titanosaur, a category of long-necked herbivorous dinosaur that includes some of the largest animals ever to walk on Earth.
Features & opinion
Further progress in artificial intelligence will require having machines teach themselves, computer scientists say. Machine learning has made impressive breakthroughs in the last decade, in large part through ‘supervised’ training: algorithms go through vast reams of data that have been previously labelled by humans (for example, about pictures being of cats rather than dogs). But ‘self-supervised’ programs (such as AlphaGo Zero) and ‘unsupervised’ techniques can sidestep human labelling, and can perform better at tasks such as discovering new laws of nature or coordinating motion. After all, babies learn how to walk by stumbling around, not by being told which moves are correct. “Humans don’t need that much supervision,” says machine-learning pioneer Yoshua Bengio.
The study of friction and lubricants, called tribology, is an often-neglected field at the confluence of physics, materials science, engineering, nanotechnology and other fields. (How friction works at the microscopic level is not completely understood.) Tribology’s economic impact is immense — for example, a large part of a car’s energy consumption comes from friction between its mechanical components. And a hot question is how to reduce friction in wind turbines to enable them to withstand stronger winds.
Researchers have engineered an enzyme that dissolves one of the world’s most commonly used plastics. The enzyme breaks down polyethylene terephthalate (PET) into its constituent monomers so it can be reused in nearly-new form, researchers tell the Nature Podcast.
Books & culture
Physics thrives on abstract thought and, often, an otherworldly detachment from reality — but up close, the all-too-human business of doing science is messy, writes Sabine Hossenfelder. She reviews an essay collection from physicist and historian of science David Kaiser that reminds us that physics, like any human activity, is influenced by the fears and fashions of history.
Andrew Robinson’s pick of the top five science books to read this week includes life on land, how we see faces and reforming capitalism.
Where I work
Carole Mundell is the chief scientific adviser at the UK Foreign and Commonwealth Office (FCO) and an astrophysicist. “The building’s grandeur contrasts with the humility of the public servants that work here,” says Mundell. “This parallels the humility needed to be a good scientist.” (Nature | 2 min read)