In the universe, as we all know, there are the Sun, the Moon, the Earth and many stars. Through our geography lessons, we know the Earth goes around the Sun and the Moon goes around the Earth. We have day and night because the Earth keeps turning all the time. 【小题1】 When our part of the Earth turns away from the Sun, it is night.

Just because the Moon is closer to the Earth than the Sun, it looks much bigger than the Sun. 【小题2】 And small things will also look bigger when they are nearer.

The Sun is big enough to give out very strong light. 【小题3】 Why? In fact, the light from the Moon comes from the Sun. The Moon looks much bigger and brighter than the stars. But actually（事实）the stars are much bigger and brighter than the Moon. 【小题4】

【小题5】 But of all the planets, only on the Earth there are living things and people can only live on the Earth, too.

On December 25, 2021, a new and exciting age of space science started when the James Webb Space Telescope was launched* into space. According to NASA, Webb is the largest and most powerful space science telescope ever built.

At first, Webb was planned to cost half a billion dollars and launched in 2007. But it turned out to be impossible. As designed, Webb’s orbit* is about 1.6 million kilometers away from the earth. It is too far for the astronauts to repair if it breaks down. So everything has to work perfectly on the first try, and it is the main reason why NASA spent nearly 30 years and 10 billion dollars getting it ready for launch.

Considered as a successor* to the old Hubble Space Telescope, Webb will allow us to look deeper into the universe than ever before. Hubble mostly sees what we see—which is known as visible light. But Webb is designed to focus on the infrared* light, which is invisible to the human eyes. That means Webb can see through dust* in the universe and make new discoveries by examining stars inside those dust clouds. It will try to collect light from the very first stars when the universe was young. By collecting the light, the telescope can see galaxies as they appeared in the past, which could help to explain how the universe began. It will also study the planets around other stars, looking for signs of life.

In order to collect the light and focus it into its camera, the mirror* Webb uses is 6.5 meters across much larger than Hubble’s 2.4-meter-wide mirror. The size advantage gives Webb 6.25 times more surface area to collect light in the universe, letting it see further and more detailed. However, the mirror also needs to be small enough to fit into a rocket to be launched into space. To fit the telescope in the rocket, engineers built the mirror with 18 honeycomb-shaped segments* that could fold up. And during Webb’s journey to the orbit, they will unfold, creating one large mirror.

Now, Webb has been in its orbit for several months, and it will send back its first images in June. By the time, the results will prove it is of great value to put so much time and money in building it.

Saturn (土星) has beautiful rings. Of planets in the solar system, Saturn’s rings are the biggest and brightest. According to scientists, however, these rings will one day disappear completely.

How did Saturn get its rings in the first place? Scientists have no sure answer. But there’s a popular theory (理论): Some comets (彗星) or small planets ran into Saturn’s moons (卫星). Saturn had at least 60 moons. And this left behind a large number of ice and rock pieces. These pieces were different in size. Some were as small as grains of sand, Others were as large as houses.

These small pieces began to travel around Saturn. Saturn’s gravity (引力) pulled them towards it. At the same time, the speed of their orbit (轨道) tried to throw them into space. Over time, these pieces of ice and rock formed rings around Saturn.

A new study, however, suggests that Saturn’s gravity is winning. About ten tons of “ring matter” is falling into Saturn every second. If this continues, the planet’s ring system will disappear completely in 100 million to 300 million years time. According to scientists, Saturn’s rings are between 10 million and 100 million years old. “We’re lucky to be able to see Saturn’s huge ring system,” one of the scientists said, “Some of the planets in the solar system only have very thin rings today. Perhaps we just missed out on seeing their huge ring systems!”