1 . Many people know that rubbish is a big problem on the Earth. What many people don’t know is that rubbish is becoming a problem in outer space too. Years of space exploration (探索) have left tons of “space junk” (太空垃圾) around the planet.

According to the reports of BBC, there are more than 22,000 pieces of rubbish in space around the Earth. And these are just the objects that are easy to see. There may be millions of smaller pieces of rubbish that we can’t see.

The pieces of space junk move around the planet at very high speeds. They move so fast that even a very small piece can become dangerous. If they crashed (碰撞) into each other, it could cause explosions that might even hurt people on the Earth. If the tiniest piece of rubbish crashed into a space shuttle (航天飞机), it could blow open a hole as big as an elephant.

To help solve this problem, countries around the world have agreed to limit the time their space tools stay in space to 25 years. Each tool must fall safely into the Earth’s atmosphere, or upper parts of the sky. There, it will burn up, and it won’t crash near the Earth.