The earth(地球)moves(移动)round the sun ,and the  36  moves round the earth. When our part of the earth turns(转) 37  the sun ,it is  38  .When our part of the earth turns  39 from the sun ,it’s Night.
The sun is  40 bigger than the moon. But sometimes the moon looks bigger than the sun , because it is much  41  to the earth.
The sun is very bright. It  42  very strong light. The moon looks quite bright, too, but it doesn’t give  43  light  44 .The light from the moon comes  45 the sun .

Comets(彗星) are parts of our solar system. Like the planets, they go around the sun.

But comets are not made of solid rocks like planets. A comet is a ball of dust, stones, and ice. Many people call comets dirty snowballs.

The “snowball” may be only a few miles across. But when the sun heats the “snowball,” much of it is changed to gases. The gases spread out and form the comet’s head, which may be thousands of miles across.

A comet moves fast in its trip around the sun. But when we see it, the comet does not seem to move. That’s because it is so far away. The moon moves fast, but when you look at it, you can’t see any motion(运动). That’s because the moon is far away.

Each year astronomers(天文学家) discover new comets. Some of them are seen only once. They make one trip around the sun and then go away out into space. The sun’s gravity cannot hold them.

Other comets, like Halley, keep returning. They have been captured by the sun. Halley’s earliest visit was probably 3,000 years ago. It may keep returning for another 3,000 years.

But every time a comet goes around the sun, the comet loses part of itself. Gases and dust are pulled out of the comet. That’s why Halley is now dimmer（暗淡的） than it used to be. Next time it visits us, in 2062, it may be even dimmer. Each visit it may get dimmer and dimmer, until it finally disappears.

1.What is this passage mostly about?

2.How does the writer help the reader understand what a comet looks like?

3.What is the most likely reason the writer wrote this passage?

Millions of stars are travelling about in space. A few form groups which travel together, but most of them travel alone.

And they travel through a universe which is so large that one star seldom comes near to another. For the most important part each star makes its journey in complete loneliness, like a ship on an empty ocean. The ship will be well over a million miles from its nearest neighbour. From this it is easy to understand why a star seldom finds another anywhere near it.

We believe, however, that some two thousand million years ago, another star wandering(漫游) through space, happened to come near our sun just as the sun and the moon raised its tides(潮汐) on the earth, so this star must have raised tides on the surface of the sun. But they were very different from the small tides that are raised in our oceans; A large tidal(潮汐的) wave must have travelled over the surface of the sun, at last forming a mountain so high that we cannot imagine it. As the cause of the disturbance came nearer, so the mountain rose higher and higher. And before the star began to move away again, its tidal pull had become so powerful that this mountain was torn to pieces and thrown off small parts of itself into space.

These small pieces have been going round the sun ever since. They are the planets.

1.Most stars are _________________________.

A. following a regular path in space    

B. moving about without a fixed course

C. seldom wandering about in the universe  

D. always travelling together

2.Some two thousand years ago, the mountain on the sun was raised probably because _____________.

   A. the star moved away from the sun

   B. another star happened to come near the sun

   C. the sun and the moon raised the tides on the earth

   D. a large tidal of wave travelled over the surface of the sun

3.The article suggests that _______________.

   A. how space formed     

B. our earth exists before the sun

   C. no one knows where the earth comes from  

D. our earth used to be a high mountain in the sun

4.The expression “the cause of the disturbance” refers to ________.

   A. the large tidal wave            B. the powerful tidal pull

   C. the star coming near the sun     D. one of sun’s planets

5. In the article, the writer mainly wants to tell us ______________.

   A. where the planets in the universe came from

   B. how the high mountains were formed on the sun

   C. that the universe is so large that we cannot imagine it

   D. why the tides over the surface of the sun were so powerful

A recent survey of 2000 parents in Britain showed that they are often afraid of science questions asked by their curious children only because they have no idea what the answer is. Here is a list of some simple questions that you can ask your parents to see if they know the answers.
Q: Why is the sky blue?
A: You probably know white sunlight is made up of seven colors. While it moves in a straight line when going through space, it starts to divide as it hits “raised area” in the atmosphere. The ones with longest wavelengths pass through easily. The blue , however , can be taken in by the gas molecules (分子) because it has a shorter wavelength , which in turn scatters (使分散) it in different directions. That’s why when you look up at the sky, it appears to be blue.
Q:Why does the moon sometimes appear during the daytime?
A: The simple answer to that is because just like any other object it is being lit by the sun. As long as it is around 45 degrees or even 90 degrees off the sun, it will receive light and be able to be seen. The only time it is not able to be seen during its 28-day orbit (轨道) around the earth is when it is right between the earth and the sun. That’s because its back , which is not lit by the sun, is facing us.
Q: Where do birds/ honeybees go in winter?
A: While the bird part is quite easy, since a lot of them get together and travel, the honeybee part is likely to puzzle your parents. It turns out that these busy insects stop being that active when the temperature drops below 50°F. Instead ,they get together in the lower central area of the hive （蜂巢）and form a ball around their queen. This helps keep both warm enough to survive the cold winter months.
【小题1】The sky looks blue mainly because the color blue in the sunlight_______.