Light travels at a speed which is about a million times faster than the speed of sound. You can get some idea of this difference by watching the start of a race. If you stand some distance away from the starter, you can see smoke from his gun before the sound reaches your ears.
This great speed of light produces some strange facts. Sunlight takes about 8 minutes to reach us. If you look at the light of the moon tonight, remember that the light rays left the moon 1.3 seconds before they reached you. The nearest star is so far away that the light that you can see from it tonight started to travel towards you four years ago at a speed of nearly 2 million km. per minute. In some cases, the light from one of tonight’s stars had started on its journey to you before you were born.
Thus, if we want to be honest, we can’t say, “The stars are shining tonight.” We have to say instead, “The stars look pretty. They were shining four years ago, but their light has only just reached the earth.”
1. Light speed is ______ sound speed
A. as fast as B. a million times slower than
C. about millions of times faster than D. about a million times faster than
2. If you stand 200 metres away from a man who is firing a gun to start a race, you will find out that ______.
A. you can hear the sound before you see the smoke B. the sound does not travel as fast as light
C. the sound will reach you before the man fires D. sound travels about a million times faster than light
3. Sunlight obviously (明显地) ______ than the light of the moon
A. has to travel a greater distance B. moves less quickly
C. travels much more quickly D. is less powerful(有力的)
4. The scientific way of saying "The stars are shining tonight" should be ______.
A. the stars have been shining all the time B. the stars seen tonight will shine four years later
C. the stars were shining long ago but seen tonight D. the starlight seen today could be seen four years ago
答案：
1. D 事实细节题。由第1段第1句可知。
2. B 推理判断题。由第1段最后一句推出。
3. A 推理判断题。由第2段的第2句(太阳光到达地球需要8分钟) 和第3句(月光到达地球仅需1.3秒) 可推出(太阳光走过的距离明显远于月光)。
4. C 推理判断题。由最后一段的最后一句They were shining four years ago, but their light has only just reached the earth可推出。