Migration (迁徙) ecologist Sissel Sjöberg had long wondered how tiny birds like the great reed warbler (大苇莺) can make it across long expanses of water or desert on their migrations. Though just half the weight of a golf ball, they fly 7, 000 kilometers between Northern Europe and sub-Saharan Africa twice a year. Now, a new study may have the answer: These nighttime birds fly well into the day — and at heights of up to 6, 000 meters, three times as high as they normally fly.

More than 4, 000 species of birds migrate across long distances each year. It’s challenging to equip small songbirds with the tracking devices that make such research possible. To see whether she could change that, Sjöberg joined the lab of Lund University Dennis Hasselquist. The pair turned to great reed warblers, relatively large songbirds that summer at a lake near Lund University. Scientists there have monitored the species’ breeding (繁殖) and behavior for 40 years.

To track the warblers, Sjöberg, Hasselquist, and colleagues equipped them with small backpacks that can monitor their journeys. As expected, the migrants usually spent their nights flying and rested during the day. But most birds that hit a water or desert crossing near dawn kept going as the sun rose, climbing high into the sky. Some birds flew higher than 6,000 meters. That’s not quite as high as the 8,000 meters geese hit, but it’s still a tall order, Sjöberg says. “We have never even imagined that songbirds regularly would fly this high.”

Such altitudes can be stressful. At 6,000 meters, oxygen isn’t enough and the temperature is below freezing. Somehow the birds are able to cope. “The ease at which they fly that high is unbelievable,” Sjöberg says.

Contrary to popular belief, people who sleep six to seven hours a night live longer, and those who sleep eight hours or more die younger, according to the latest study ever conducted on the subject. The study, which has tracked the sleeping habits of 1.1 million Americans for six years, weakens the advice of many sleep doctors who have long recommended that people get eight or nine hours of sleep every night.

“There’s an old idea that people should sleep eight hours a night, which has no more scientific basis than the gold at the end of the rainbow,” said Daniel Kripke, professor of psychiatry (精神病学) at the University of California at San Diego who led the study published in a recent copy of JAMA Psychiatry.

The study was not designed to answer why sleeping longer may be harmful or whether people could extend their lifespan by sleeping less.

But Kripke said it was possible that people who slept longer tended to suffer from short-term absence of sleeping, a condition where weak breathing puts stress on the heart and brain. He also stressed that the need for sleep was similar to that for food, where getting less than people want may be better for them.

The study quickly caused warnings and criticism (批评), with some sleep experts saying that the main problem of America’s sleep habits was deprivation (剥夺), not sleeping too much.

“None of this says sleep kills people,” said Daniel Buysse, a psychiatrist at the university of Pittsburgh Medical Center.

“You should sleep as much as you need to feel awake, alert and attentive the next day,” Buysse added. “I’m much more concerned about people short-changing themselves on sleep than people sleeping too long.”

“Sleeplessness produces a variety of health consequences that were not measured in the study,” critics said.

It is hardly surprising that clothing manufacturers (生产商) follow certain uniform standards for various features (特征) of clothes. What seems strange, however, is that the standard adopted for women is the opposite of the one for men. Take a look at the way your clothes button. Men’s clothes tend to button from the right, and women’s from the left. Considering most of the world’s population—men and women—are right-handed, the men’s standard would appear to make more sense for women. So why do women’s clothes button from the left?

History really seems to matter here. Buttons first appeared only on the clothes of the rich in the 17th century, when rich women were dressed by servants. For the mostly right-handed servants, having women’s shirts button from the left would be easier. On the other hand, having men’s shirts button from the right made sense, too. Most men dressed themselves, and a sword drawn from the left with the right hand would be less likely to get caught in the shirt.

Today women are seldom dressed by servants, but buttoning from the left is still the standard for them. Is it interesting? Actually, a standard, once set, resists change. At a time when all Women’s shirts buttoned from the left, it would have been risky for any single manufacturer to offer women’s shirts that buttoned from the right. After all, women had grown so used to shirts which buttoned from the left and would have to develop new habits and skills to switch. Besides, some women might have found it socially awkward to appear in public wearing shirts that buttoned from the right, since anyone who noticed that would believe they were wearing men’s shirts.