News and notes about science
Do your shoelaces keep coming undone? Engineers explain why
Researchers in California have unraveled one of life’s enduring mysteries: Why do shoelaces come undone?
When running, the foot hits the ground at about seven times the force of gravity. The knot stretches and relaxes in response. As it loosens, swinging legs apply an inertial force on the free ends of the laces, and pretty soon they are flopping around.
To fix the problem, fix the knot. A weak knot will typically have one loop pointing toward the toes and one toward the ankle. A stronger knot, usually based on a square knot, typically has the loops oriented on opposite sides. — Christopher Mele A lizard with scales that behave like a computer simulation
The ocellated lizard is born rusty brown with white polka dots. By the time the lizard has sexually matured, some 4,000 scales along its back are all black or green. Many of these scales will flip between black and green.
According to a new study, the lizard’s patterns unfold like a type of computer simulation called a cellular automaton, which describes how one component affects a series of others.
Alan Turing proposed that patterns in living things emerge from a feedback loop between chemicals that activate and inhibit one another. The researchers modified Turing’s mechanism and confirmed that its patterns behaved like a cellular automaton — the first living example, researchers say. — Steph Yin Saber-toothed cats paid a stiff price for lunch
About 12,000 years ago, the saber-toothed cat stalked grasslands across the Americas. Catching meals came at a price.
Paleontologists analyzed bones from more than 340 saber-toothed cats retrieved from the La Brea Tar Pits in Los Angeles. Compared with another predator found in the pit, the dire wolf, the cat was more likely to have injured its shoulder blades. But more than half of the injuries to the cats occurred on the spine, mostly the lower parts — most likely suffered as they tried to wrestle large prey to the ground. — Nicholas St. Fleur
Photos of Jupiter from NASA spacecraft, both near and far
The Juno spacecraft made its fifth just-abovethe-cloud-tops dive of Jupiter last month, its eight instruments gathering data on the planet as it accelerated to 129,000 mph.
The probe snapped close-ups of the gigantic storms swirling across the planet’s surface, including one just south of a famous white oval (also a storm), and another that appears only as a dark blotch amid the clouds. The distance, 415 million miles, is the closest that Earth gets to Jupiter, which makes it a good time for Hubble to perform a once-a-year survey of the solar system’s largest planet. Jupiter’s atmosphere appears to be more turbulent than in the past couple of years, said Amy A. Simon, an astronomer at the Goddard Space Flight Center who led the observations. — Kenneth Chang
Valiant in battle, these ants rescue their wounded
Megaponera analis, a species found in sub-Saharan Africa, hunts in groups for termites. Larger ants break open the nest; smaller ants rush in to grab prey.
But the injury rate is high among the invaders. So the ants rescue their injured buddies. This behavior allows the ants to maintain a colony size 28.7 percent larger than they otherwise could, researchers calculated. — Nicholas Bakalar
An ice scientist’s worst nightmare
Earlier this month, sections of ancient ice cores extracted from the Canadian Arctic melted because of a freezer malfunction in a lab at the University of Alberta.
Ice cores contain gas bubbles, pollen, dust particles and chemical isotopes that give scientists clues about what Earth’s temperature and atmosphere were like when the ice caps first formed.
Among those affected were some from Baffin Island’s Penny Ice Cap, which contained 22,000 years’ worth of atmospheric information. — Tatiana Schlossberg