Contents 1
1．Why is the solar system the way it is？ 1
2．What keeps the sun shining？ 3
3．Why do sunsets look red？ 5
4．What is the earth made of 7
5．Why are eclipses so rare？ 9
6．What is a constellation？ 11
7．What is the brightest star？ 13
8．What is a comet？ 15
9．Why do astronomers think there may be life on Mars？ 17
10．Why are there different kinds of clouds？ 19
11．What is a nebula？ 22
12．Why is the ocean salty？ 24
13．Which is the deepest ocean？ 26
14．What causes the waves？ 28
15．What are tidal waves？ 30
16．What is a whirlpool？ 32
17．What is the Gulf Stream？ 34
18．Why does water flow out of a spring？ 36
19．How were the mountains made？ 38
20．Why are there so many different kinds of rocks？ 40
22．What are fossils？ 44
23．How are icebergs formed？ 46
21．How are caves formed？ 48
24．When did the Ice Age end？ 48
25．Why do we still have glaciers today？ 50
26．Why do volcanoes appear only in certain places？ 52
27．Where do most earthquakes occur？ 55
28．How does the weatherman know what to say? 57
29．Why do we have different seasons？ 59
30．What is the jet stream？ 61
31．What is humidity？ 63
32．What is a storm？ 65
33．Why does thunder follow lightning？ 67
34．Why is it hot at the Equator？ 70
35．Is the South Pole as cold as the North Pole？ 72
36．Why is a desert dry？ 74
37．What is smoke？ 77
38．What is smog？ 79
39．What is gas？ 81
40．What is helium？ 84
41．What is atomic energy？ 86
42．What is radium？ 88
43．What is radioactivity？ 90
44．What are X-rays？ 92
45．What are cosmic rays？ 95
46．What is the sound barrier？ 97
47．What causes an echo？ 100
48．What is oxygen？ 102
49．What is water？ 104
50．How is soil formed？ 106
51．Why are there different kinds of sand？ 109
52．How is coal formed？ 111
53．What is a mineral？ 114
54．What is silver？ 116
55．What is quicksilver？ 119
56 What is quartz？ 121
57．What is mica？ 123
58．What is a gem？ 125
59．Do the Northern Lights appear in the South？ 128
60．Where did the stars come from？ 130
Glossary 132