1What kinds of celestial bodies can be seen when we look at a clear night sky?
2How far do you think this sky extends?
3Write down the contribution made by Hubble, Lemaitre and Hawking to the big bang theory.
4What are space and the universe? Bring out the difference between them.
5What is one light year, and how many kilometres is it?
6What is the observable universe, and how big is it?
7Write a short account of the big bang theory.
8What is the primeval atom, and who gave it that name?
9How did the universe take shape after the big bang? Write the stages in order.
10What is astronomy, and why does it depend so much on observation?
11Convert 46 billion light years into kilometres.