Only humans speak using words. But all kinds in the animal world can communicate in one way or another. Maybe you have heard about the way bees dance around to send messages to each other and the way dogs bark in different ways to give warnings, to be friendly or to be playful. But did you know about infrasonic communication used by elephants? This is how it works:

    Humans hear low sounds like thunder rumbling in the sky. But we don't hear sounds lower than this. However, animals such as elephants and hippos can hear much lower sounds than humans can. And what's more, they can make those low sounds as well, and they use them to communicate with each other. This is known as infrasound.

    The amazing thing about infrasound is that it travels over several kilometers. Higher-level sounds like the one people can hear, don't travel well through walls, leaves, trees and so on, which is why we can't hear sounds from more than 100 meters away. But infrasound is much stronger and things like grass and trees have no influence on it. Therefore, it can travel much further. Elephants can hear infrasonic calls from four kilometers away!

    There have been reports of people watching groups of elephants feeding or resting and then the elephants suddenly all stopped what they were doing for no reason at all. They obviously heard a warning call from a long way away, but the people didn't hear a sound. In places like a zoo or wildlife park where you can get nearer to animals, it is a bit easier to sense when infrasonic sounds are made. When you stand near mother elephants with their babies in a zoo, you may notice a slight rumbling in the air every few minutes—not loud or strong, but clearly noticed. This is infrasonic communication—the mother elephants “talking” to their babies.

Huizhen High School has a building with 1 own "forest". The rooftop (楼顶) park of the school gives people a place to see the 2 city. 

Ma Di, the 42-year-old designer of the school, said that he got the idea from his 3 Sunny. "The design of her school makes her feel 4 sometimes," Ma said. "She told me that the classrooms are too small, and the hallways are small, 5 . Sometimes it feels like there is no bright color in the school. As her father, I have wanted to make some changes."

To Ma Di, allowing students to have times with no real purpose is as important as 6 them in the classroom. "In my design, there are no rules, no traditional idea of rooms and floors," said Ma. For example, Ma puts a huge " 7 in the air" into a teaching building, to get students to feel close to nature. There are hallways going through tree tops in the forest, 8 students can move up and down in the "forest". Some rooms are also 9 small aquariums (水族馆) and radio stations, where they can have lots of fun. 

Thanks to his creative ideas, Ma's design 10 the World Building of the Year 2023 award at the 2023 World Architecture (建筑) festival.

Doing "Clean" Exercise

When you go for a run outside, chances are that you'll find rubbish all around you. Do you just go past it, or do you stop to pick it up? If you choose the second, you are part of the latest popular sport in the West: plogging. 

The word"plogging" comes from the Swedish phrase"plocka upp (pick up)" and the English word"jogging (running slowly)". What a plogger needs is a rubbish bag and a pair of gloves to protect his or her hands. While collecting rubbish, ploggers learn to classify (分类) and deal with it correctly too. 

Plogging seems simple but it does a lot of good to both the environment and your health. It can not only make the world greener, but also get you full body exercise. For example, a30- minute plogging burns around 288 calories(卡路里), compared to 235 calories burnt from just jogging. 

So next time you go out jogging, why not carry a rubbish bag and collect some rubbish along the way? Your body and the environment will thank you. 

 Earth Day, which falls on April 22, is a day to call on more people to protect the natural world. This year's theme"Planet VS. Plastic" is especially important because plastic is harming our environment in many ways. Plastic doesn't break down easily. {#blank#}1{#/blank#} To fight against plastic pollution, we all need to do something.

 Governments can make rules to limit(限制) the use of plastic and encourage people to recycle. Businesses should find ways to use less plastic or use recycled plastic instead.

International cooperation (合作) is of great importance, as many environmental problems need worldwide support. {#blank#}2{#/blank#}

 Schools can help too. {#blank#}3{#/blank#} By taking part in activities like zero-waste events at school, we will be more likely to make proper choices in our daily lives. We can also share what we know with our friends and families.

{#blank#}4{#/blank#} We are advised to use reusable shopping bags and glass bottles instead of plastic ones. It's a good idea to try to buy something without a lot of plastic packaging(包装). Even small changes in our daily habits can be helpful.

 Earth Day is a perfect chance to have our voice heard. {#blank#}5{#/blank#} Let's work together towards a greener planet.