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Mercury
Mars
Venus
star
Galaxy
planet
It’s a planet.
No, it isn’t.
Saturn.
The earth.
1. How long has there been life on the earth?
2.Have scientists found life on other planets?
For hundreds of millions of years.
No, they have not found life on any other planets yet.
1. How many planets go around the sun?
A. Six B. Seven C. Eight D. None
2. Will scientists find life on seven other planets? Why?
No, they won't. Because none of them has an environment like that of the earth.
3. Give a right order: small—large. solar system, earth , Galaxy, sun
_______—_________—__________—_______
4. How large is the universe?
earth
sun
solar system
Galaxy
It is impossible to imagine.
1. What have scientists done to learn about the universe?
Scientists have sent spaceships to the planet Mars to take photos. They have even sent spaceships to travel outside the solar system.
2. Have spaceships travelled far enough to reach other stars?
No, they haven’t.