【推荐2】The French Danone company is the latest to replace some plastic water bottles with aluminum (铝) cans. Competitors like Coca-Cola, PepsiCo and Nestle have also started selling water in aluminum cans.

Replacing plastic water bottles that pollute the seas with recyclable aluminum cans should be an easy way to help the environment, right?

Maybe not.

Aluminum cans might result in less ocean waste, and the metal containers also are lighter than glass or plastic bottles, but they also come with their own cost to the environment. The production of an aluminum can is estimated to release two times as much carbon dioxide into the air as a plastic bottle.

“That’s the dilemma you’re going to have to choose between,” said Ruben Griffioen, an official at beermaker Heineken. He said his company was Lrying to reduce the use of plastic bottles.

Bruce Karas of Coca - Cola North America agreed. He said, “There’s a mix. There are some things that are not that desirable, but if you have five good things and one that isn’t, we’ll all have to make decisions.” He added, “It’ll never be that clean.”

Bottled water is a 19 billion industry. Although its use of cans is increasing, experts say cans are unlikely to completely replace plastic bottles.

Aluminum is costlier than plastic so canned drinks mean higher prices for buyers. Another major consideration is user convenience-cans stay open while bottles can be reclosed. More importantly, there is one barrier to ending the use of plastic water bottles: There may not be enough cans to go around. Beer and wine makers are now also increasingly using aluminum.

【推荐3】On a boat near Costa Rica, a team of marine biologist is helping a turtle. The animal is having trouble breathing, and the team discovers why—there is something inside its nose. A scientist tries to extract the object, but the turtle cries in pain. Finally after eight long minutes, a long object is pulled out. It is a 10 centimeter plastic straw.

The video of the turtle’s rescue has been viewed millions of times on YouTube. It has helped raise awareness of a growing problem: The world’s seas are full of plastic. Since 2000, there has been a huge increase worldwide plastic production, but we recycle less than one-fifth of it. A lot of this plastic waste ends up in the ocean. Today, scientists think about 8.1 billion kilograms goes into the sea every year from costal regions. Most of this plastic will never break into little pieces.

This ocean plastic hurts millions of sea animals every year. Some fish eat plastic because it is covered with sea plants, and it looks and smells like food. “In some cases, eating sharp pieces of plastic can seriously hurt sea animals and even result in death,” says marine biologist Matthew Savoca.

Plastic is useful to people because it is strong and lasts a long time, but this is bad news for sea creatures who eat or get stuck in it. According to Savoca, single-use plastics are the worst. These are items that are used only once before we throw them away. Some common examples include straws, water bottles, and plastic bags. About 700 sea species have been caught in or have eaten this kind of plastic. Luckily, the turtle survived and was released back into the ocean. How will plastic affect sea animals in the long term? “I think we’ll know the answers in 5 to 10 years’ time,” says an expert from Columbia University. But by then, another 25 million tons of plastic will already be in the ocean.

【推荐1】That people often experience trouble sleeping in a different bed in unfamiliar surroundings is a phenomenon known as the “first-night” effect. If a person stays in the same room the following night they tend to sleep more soundly. Yuka Sasaki and her colleagues at Brown University set out to investigate the origins of this effect.

Dr. Sasaki knew the “first-night” effect probably has something to do with how humans evolved. The puzzle was what benefit would be gained from it when performance might be affected the following day. She also knew from previous work conducted on birds and dolphins that these animals put half of their brains to sleep at a time so that they can rest while remaining alert enough to avoid predators（捕食者）. This led her to wonder if people might be doing the same thing.

To take a closer look, her team studied 35 healthy people as they slept in the unfamiliar environment of the university’s Department of Psychological Sciences. The participants each slept in the department for two nights and were carefully monitored with techniques that looked at the activity of their brains. Dr. Sasaki found, as expected, the participants slept less well on their first night than they did on their second, taking more than twice as long to fall asleep and sleeping less overall. During deep sleep, the participants’ brains behaved in a similar manner seen in birds and dolphins. On the first night only, the left hemispheres（半球）of their brains did not sleep nearly as deeply as their right hemispheres did.

Curious if the left hemispheres were indeed remaining awake to process information detected in the surrounding environment, Dr. Sasaki re-ran the experiment while presenting the sleeping participants with a mix of regularly timed beeps（蜂鸣声）of the same tone and irregular beeps of a different tone during the night. She worked out that, if the left hemisphere was staying alert in a strange environment, then it would react to the irregular beeps by stirring people from sleep and would ignore the regularly timed ones. This is precisely what she found.