The Diving Bell and the Spider
The water spider spends its life underwater but it needs oxygen to breathe. So when it visits the surface, the spider grabs a bubble of air that sticks to its hairy abdomen. It deposits this bubble into a little silk “diving bell” and breathes from the bell like a tank. The bell functions as a gill: as the spider removes oxygen from the bell, more oxygen flows in. Using a microscopic oxygen sensor, researchers from the University of Adelaide in Australia and Humboldt University in Germany determined how gases move across the bell's surface and found that the spider can stay underwater for up to 24 hours, they report this week in the Journal of Experimental Biology. The spider keeps the bell's volume proportional to its oxygen needs: To eat, it enlarges the bell, puts its food inside, and crawls in after it. Females lay their eggs inside the bell and enlarge it as the brood grows.


On the Shoulders of Giants

Talk about international collaboration. When Polish astronomer Johannes Hevelius began working on his 1687 map of the stars, he wrote to German theologian Henry Oldenburg, secretary of the Royal Society in England. The request: to locate the 15th century star map of astronomer Ulugh Beg of Samarkand and translate it from Persian.
The Royal Society fulfi lled his request, and the map guided Hevelius’s new observations. This frontispiece to Hevelius’s map pays homage to Beg; as Hevelius presents the book to Urania, muse of astronomy, the top 10 astronomers of all time look on. Beg is third from left.
“He crossed many centuries with that image, putting many people shoulder to shoulder,” says astrophysicist Rim Turkmani, curator of Arabick Roots, which opened 9 June at the Royal Society in London. “It’s a nice gesture from him to say thank you.” The exhibition’s letters, manuscripts, diagrams, and instruments chronicling the flow of scientifi c knowledge from the Arab world to Europe in the 17th century will be on view until November.