We have always been interested in the moon. 2, 000 years ago, people already knew it moves around the earth and where it would be in the sky at different times of the year. At that time, everything about the moon was learned by watching it carefully in the sky.
When scientists could use telescopes to study the moon more closely, their ideas began to change. They could see the moon was made of rocks. Most scientists thought moon rocks would be different from those on the earth. This was because they believed the moon had once been a planet that had been caught in the earth’s gravity (重力) millions of years earlier.
In 1969, moon rocks were finally brought to the earth and studied. Much to their surprise, scientists found that, except for water, the moon and the earth were made of the same things. Once again new ideas were needed for this new information.
After years of study, most scientists now think that the moon was once part of the earth. They believe very early in its history, maybe 4 billion years ago, something about the size of Mars hit the earth. This sent billions of rocks into space around our planet. These rocks slowly joined together and after many years became the moon.
In the future, though our ideas about the moon may change again, we will still be interested in it.
【小题1】Before 1969, most scientists thought the moon was ________.| A．part of the earth billions of years earlier | B．older than the earth |
| C．caught by the earth’s gravity | D．made of the same things as the earth |
| A．The earth was once part of the moon. | B．The moon used to be part of the earth. |
| C．Mars will hit earth in the near future. | D．Rocks will join together to become another moon. |
| A．new information brings new ideas | B．scientists in the past were not clever |
| C．we now know everything about the moon | D．scientists are so clever that they know everything |
