A 3D shape of constant width as seen from three different angles. The middle view resembles a 2D Reuleaux triangle
Andriy Prymak et al. 2024/SageMath/Danylo Radchenko
Mathematicians have reinvented the wheel with the discovery of shapes that can roll smoothly when sandwiched between two surfaces, even in four, five or any higher number of spatial dimensions. The finding answers a question that researchers have been puzzling over for decades.
Such objects are known as shapes of constant width, and the most familiar in two and three dimensions are the circle and the sphere. These aren’t the only such shapes, however.…
Solar drone with wingspan wider than jumbo jet could fly for months
The Skydweller droneSkydweller A solar-powered surveillance drone with a wingspan larger than a Boeing 747 jumbo jet could fly for...
Why Trump’s order targeting ‘woke’ AI may be impossible to follow
US President Donald Trump displays a signed executive order at an AI summit on 23 July 2025 in Washington, DCChip...
Sprinkling limestone on farms may offer an unexpected climate win
Farmers spread lime on pastures to improve the quality of the soilWayne HUTCHINSON/Alamy The centuries-old practice of spreading crushed limestone...
Your chance of having a boy or girl may not be 50/50
A woman’s age may determine whether she has only sons or daughtersMarko Pekic/Getty Images You may assume that a woman’s...
