We often see beautiful butterflies flying around us. If you have ever tried to catch a resting butterfly, you know it is surprisingly difficult. A new study helps explain why.

Previous research had suggested that a butterfly’s overhead wing clap forces the insect forward. Researchers thought the wing clap likely formed a pocket of air that shoots out like a jet. But no one had tested that until now.

To analyze their flight, they placed six butterflies one at a time inside a wind cave which was filled with smoke and then used a laser (激光灯) to light up the smoke just behind the butterfly. Four high-speed cameras were placed in the cave to take photos of the movement of the butterfly and the smoke as the butterfly was taking off. This let the researchers create a 3D picture of that air movement as the insect flapped its wings.

They analyzed a total of 25 takeoffs by six butterflies. Each included up to three wing beats after takeoff. The butterflies proved more likely to clap their wings together during the first few wing beats than later in flight.

The photos show that forces created by the wings give rise to a flight path. The butterflies rise as their wings move down and shoot forward as their wings move up. A wing clap on takeoff, paired with a quick turn, allowed the butterflies to fly away quickly. They also noticed the wings formed an air pocket just before clapping and that the wings’ flexibility and this pocket improved the jet force created by the clap.

“The study is exciting,” says Ayodeji Bode-Oke, a mechanical engineer in Charlottesville. That means “we have solved the longtime puzzle about how butterflies fly, and it proves nothing is impossible on the road of scientific research. I can’t wait to learn about how the study might inform designs for small flying vehicles.”

Learning a second language is tricky at any age (and it only gets tougher the longer you wait to open that dusty French book). Now, in a new study, scientists have pinpointed the exact age at which your chances of reaching fluency in a second language seem to plummet: 10.

The study, published in the journal Cognition, found that it’s “nearly impossible” for language learners to reach native-level fluency if they start learning a second tongue after 10. But that doesn’t seem to be because language skills go downhill. “It turns out you’re still learning fast. It’s just that you run out of time, because your ability to learn starts dropping at around 17 or 18 years old,” says study co-author Joshua Hartshorne, an assistant professor of psychology at Boston College.

Kids may be better than adults at learning new languages for many reasons. Children’s brains are more plastic than those of adults, meaning they’re better able to adapt and respond to new information. “All learning involves the brain changing,” Hartshorne says, “and children’s brains seem to be a lot more skilled at changing.”

Kids may also be more willing to try new things (and to potentially look foolish in the process) than adults are. Their comparatively new grasp on their native tongue may also be advantageous. Unlike adults, who tend to default(默认)to the rules and patterns of their first language, kids may be able to approach a new one with a blank sheet of paper.

These findings may seem discouraging, but it was heartening for scientists to learn that the critical period for fluent language acquisition might be longer than they previously thought. Some scientists believed that the brief window closes shortly after birth, while others stretched it only to early adolescence. Compared to those estimates, 17 or 18 - when language learning ability starts to drop off - seems relatively old.

“People fared better when they learned by immersion(沉浸), rather than simply in a classroom. And moving to a place where your desired language is spoken is the best way to learn as an adult. If that’s not an option, you can mimic an immersive environment by finding ways to have conversations with native speakers in their own communities,” Hartshorne says. By doing so, it’s possible to become conversationally proficient - even without the advantage of a child’s brain.

When micro-plastics end up in farm fields, the pollution can damage plant growth. But two young researchers now report that combining fungi (真菌) with certain farm wastes can partly overcome that problem.

May Shin, 20, and Jiwon Choi, 18, met in a research design class at the Fryeburg Academy, a high school in Maine. May had desired to explore how micro-plastics might affect the ecosystem. Jiwon was crazy about plants and fungi. The young scientists cooperated to test how long-lived plastics might affect farm crops.

Scientists have shown certain fungi can aid root growth and a plant’s nutrient uptake. Those organisms are named arbuscular mycorrhizal fungi (AMF). Certain farm wastes, like straw, can provide nutrients to plants and help stabilize their roots. Such wastes are also known as mushroom substrate (基质) and people often grow mushrooms in them.

May and Jiwon planted over 2,000 scallion (大葱) seeds in pots of soil. Half the seeds got soil polluted with micro-plastics. The rest grew in plastic-free soil. The plants then were further divided into four groups. The young scientists added AMF to the soil in one group. Another group had a top layer of mushroom substrate. A third group got both treatments. The last group got none. For three weeks, the pair tracked how many scallions sprouted (发芽) in each group and measured the plants’ height once each week.

About twice as many scallions sprouted in clean soil compared to that containing plastic bits. But among plants surviving in the polluted soil, a combination of AMF and mushroom substrate helped them out. Those getting both treatments grew 5.4 centimeters per week. That was faster than either of the treatments alone or those getting none.

Jiwon and May then looked at the plant roots with a microscope. Where AMF had been added, it grew into those roots. That increased the scallion roots’ surface area, May said, which should promote their uptake of nutrients. So “I see this project as coming up with a sustainable solution for plant growth in polluted soils,” said May.