Comprised of rock, dust, gases and ice, comets come from the outer reaches of the Solar System, where the temperatures are much colder.

由石块，尘土，气体和冰组成的彗星来自于太阳系外部那里温度比较低。

Today you learned the Milky Way is a disk galaxy, a collection of dust, gas, and hundreds of billions of stars, with the Sun located about halfway out from the center.

今天你学到了银河系是一个盘状星系，由尘埃、气体和数千亿颗恒星组成，太阳位于离中心一半远的地方。

" Not half so bad as all this dust, gas, heat, and noise. What do you suppose lungs are made of" ? demanded Mac, ready for a discussion then and there.

“不及所有这些灰尘、气体、热量和噪音的一半糟糕。你认为肺是由什么构成的” ？要求麦克，准备当场讨论。