【推荐3】The Garbage Project started at the University of Arizona in 1973. Since then, the students and teachers in it have studied the modern garbage in different cities.

To study the garbage, the students had to travel to landfills (填埋场) , the places where cities bury their garbage. While the students were studying the garbage they wore special clothes. Students were very careful when they opened bags of garbage.

One important thing the students have learned from studying the garbage is that the garbage in landfills disappears very slowly. That was surprising to both the students and many scientists who had thought that about 70 % of the garbage in landfills would disappear quickly. Even in cities where it rains a lot, the students found newspapers from 1948, 40-year-old hot dogs, and vegetables from 1970. And the students also found many more empty bottles of cola than they expected.

How to dispose of our garbage well depends on what kind of garbage it is: regular garbage, dangerous materials, or recyclable materials, such as newspapers and glass bottles. Regular garbage goes to regular landfills. Dangerous materials are harmful to people's health and the environment. They shouldn't go into regular landfills.

Homes are full of dangerous waste. One kind of the dangerous waste in homes is batteries. When batteries are buried directly in a landfill, they often break open. The poison inside them moves through rain water to the bottom of the landfill. Then it can pollute the natural water in the ground.

Another dangerous waste from homes is motor oil. When people pour old motor oil on the ground or throw it in the garbage, it pollutes the environment.

Our garbage problem is not new, but as the world's population continues to grow, it will become a bigger and bigger problem.

【推荐2】After a tiring day at the office, you find it hard not to smile when you’re greeted by an exciting and joyful dog. But it’s not just the happy shouting and wriggling (扭动) tail that strike our heartstrings. A new study shows that dogs’eyes filled with tears when reunited with their owners cause effect that brings out our love. The findings appear in Current Biology.

Takefumi Kikusui watched with interest when his dog was feeding her puppies, her face became so cute. Kikusui, a professor of veterinary(兽医) medicine at Azabu University in Japan, realized that his lovely mama dog had tears in her eyes. That possible connection between unbearable cuteness and tears sent him to the lab.

In the test, he and his team first measured the baseline tear volumes when dogs were together with the owner in their house. Then quickly, the owner would leave and stay hidden away from it for five or six hours. When the owner came back, they measured tear volume again. And found that the reunion with the owner raised tear volume. But it only worked with the dog’s owner. If reunited with the familiar caretaker in the dog care center, there was no increase in tears.

The researchers doubted that the tearful reaction was caused by oxytocin, a hormone(荷尔蒙) linked with social bonding. So they applied oxytocin to the dogs’ eyes. And, the dogs grew weepy. But why? To find out the reason for this easy-crying behavior, they showed volunteers a couple of dog head pictures. One was a normal dog face. And the other was a teary dog face in which they added man-made tears. The volunteers were more likely to want to hug and care for the one with big, wet puppy-dog eyes.

Dogs turn on the waterworks and their owners roll over. Now, that’s quite a clever trick!

【推荐1】The DNA of 6.7 million species could be stored inside the Moon in case there's a disaster that destroys life on the Earth. Scientists have a plan to create a “lunar ark”, which is like “Noah's Ark”, the ship in which Noah saved animals from a food, according to the Bible. The lunar ark would contain millions of samples of reproductive cells and seeds from all he 6.7 million known plant, animal and fungi species on the Earth. The researchers think the lunar ark could be put in the hollowed out lava tubes that exit on the Moon's surface. It is thought that these cave-like networks were created by lava billions of years ago. Robots would be sent inside the tubes to start building the ark.   

When the ark is complete, scientists think it could be powered by solar panels on the surface so that all the samples inside can be kept at cryogenic temperatures without the risk of being rotten over decades, if not centuries. I will also ne things like an airlock and lighting for human visitors.

Researcher Jekan Thanga and a team of students from the University of Arizona in the US have mapped out the theory. They think it would take 250 rocket trip to the Moon to complete the lunar ark. “Earth is naturally likely to change suddenly,” Professor Thanga said, “It's safer to sore the samples on the Moon in case the Earth is destroyed.”

The lunar ark concept was presented by the researchers at the IEEE Aerospace Conference in early March. They listed super-volcanoes, asteroid impacts and climate change as reasons we might need to store samples of life in case we need to start again. Thanga said: “The environment and human civilization are both very fragile.” Not all of the technology needed to make the ark exists yet but the scientists think it could be made reality within the next 30 years.

【推荐2】The great flight of the Chinese astronaut (宇航员) Yang Liwei in 2003 made China the third country in the world to send a person into space. His journey of 600, 000 kilometres took one day. But the training of astronauts like Yang Liwei takes years and is very hard.

As a basic requirement, trainee (受训者) astronauts must be fighter pilots with over 600 hours of flying. This means that they have experience of flying at high speed and dealing with changes in air pressure. As well, they must have at least 4 years of college education and must be very strong and healthy. A normal trainee is 25-35 years old, weighs 55-70 kilogrammes and is 1. 60-1. 72 metres tall.

Pilots with the basic requirements then go through a long period of examination to see if they are fit for training. They stay in hospital for a month of tests, which check for any kind of physical (生理的) weakness. Moreover, they have to sit in a chair which turns around at high speed for 15 minutes, to find out how their body works. There are also mental tests to find out how they will deal with living in a very small room, and how well they will respond to dangers and solve problems.

Once they are chosen, the pilots go through a five-year course to prepare them for space flights. At the end of the five-year programme, there are final tests for the trainees. After passing these tests, they have succeeded in becoming real astronauts.

【推荐3】Before Starlink, a new satellite Internet system from the company SpaceX, most satellite Internet service was based on satellites that constantly remained above one point on Earth-over Chicago, for example, which means that signals from farther away need to travel a long distance, causing delays. Starlink has a web of satellites moving constantly in a low orbit around the Earth. Because the satellites are closer, the speeds are faster, which makes the service better for things that need to happen without delays, like holding meetings over the Internet.

To get on the Internet with Starlink, users need a terminal(终端). The terminal tracks the web of satellites and communicates with them to provide Internet service. The service works as long as the terminal is placed where it can “see” the sky.

Starlink currently works in 31 countries, but SpaceX plans to expand the service to cover the whole world. The clearest need for this kind of service is in remote areas. Starlink terminals also work from moving objects, so SpaceX is also planning to offer service on transportation, like planes, trains, and boats.

Starlink currently has over 2, 100 satellites in orbit around Earth. SpaceX has permission from the US government to launch 12, 000 satellites, and it has asked for permission to launch as many as 30, 000 more.

Astronomers have complained that Starlink satellites are causing light pollution. This makes it harder to study things in space with satellites getting in the way. SpaceX has worked to abate the light from Starlink satellites. But scientists say the satellites still make their work harder. This will get worse as more satellites fill the skies.

There are also concerns about Starlink satellites crashing into other satellites or spacecraft. In 2019, a European satellite had to move to avoid coming close to Starlink satellites. Still, Starlink has been useful in emergencies. When the island nation of Tonga lost Internet service after a volcano erupted in January, 2022, SpaceX was able to provide temporary service using Starlink.