1.Which of the following is not a general difference between a planet and a star?
2.Our solar system consists of _________.
3.Which of the following best describes what we mean by the universe?
4.What do astronomers mean by the Big Bang?
5.Based on observations of the universal expansion, the age of the universe is about _________.
6.A television advertisement claiming that a product is light-years ahead of its time does not