A Million Whys: The City Expedition for Curious Kids

All 150 questions

Tap a question to watch its video and read the answer.

Expedition 1: Skyscrapers & Big Buildings

1. What happens on a building site before the first floor goes up?
2. Why do tall buildings have a steel skeleton?
3. When was the first skyscraper built?
4. How tall is the tallest building in the world?
5. How does a tower crane grow taller as the building grows?
6. How does concrete get to the top of a tall building?
7. Why can a skyscraper have walls made mostly of glass?
8. How does the golden ball inside Taipei 101 keep the tower steady?
9. Why do skyscrapers have metal rods on top?
10. How do elevator brakes and floor sensors keep riders safe?
11. How do tall buildings stay safe from fire?
12. What makes the CN Tower in Toronto so special?
13. How do window washers reach the 60th floor?
14. What makes a skyscraper green?
15. What gear keeps skyscraper builders safe up high?
16. What is on the roof of a skyscraper?
17. What do architects and engineers each do?
18. Why is it so windy at the foot of a tall building?
19. Why are some skyscrapers rounded, tapered, or twisted?
20. Can a skyscraper be made of wood?
21. How are old buildings taken down safely?
22. How do builders make sure a tall building is straight?
23. How do engineers know how much weight a floor can hold?
24. How do big buildings stay warm in winter and cool in summer?
25. How do computers help design a building before it is built?

Expedition 2: Streets, Traffic & Getting Around

26. How do traffic lights know when cars are waiting?
27. Why do crossing guards hold up a big STOP sign?
28. Why are stop signs red octagons?
29. How do road builders make a road layer by layer?
30. Why are some roads black and some light gray?
31. How do potholes form each winter and spring?
32. Why do roads have painted lines, and what do solid and dashed lines mean?
33. How do speed bumps make cars slow down?
34. Why do roundabouts help traffic flow?
35. Why do traffic jams sometimes happen even without an accident?
36. How does a phone know how slow the traffic is?
37. Why do some cities have lanes just for buses?
38. Why do some city vehicles hang on wires above the street?
39. Why do you feel wind in a subway station before the train comes?
40. How does an escalator work?
41. Why do bike lanes keep cyclists safer?
42. How do ambulances and fire trucks get through busy traffic?
43. Why does crossing at the corner and looking both ways work?
44. Why do different countries drive on different sides of the road?
45. How do street names and house numbers help people find places?
46. Why do some cities have ferries?
47. How do parking garages stack so many cars?
48. Why are more city buses powered by electricity?
49. How do traffic engineers count cars?
50. Why do highway ramps curve in big loops?

Expedition 3: Hidden City Systems

51. How does water travel through a city's pipes to your tap?
52. Why do water mains sometimes break?
53. How do fire hydrants work?
54. Why are manhole covers round?
55. Why does steam sometimes rise from street grates?
56. How do city workers look inside a sewer pipe?
57. What happens at a wastewater treatment plant?
58. Why do some sewers overflow when it rains hard?
59. Why are some city wires buried while others hang on poles?
60. What are the big green boxes at street corners?
61. How does a cell tower pass your phone call along?
62. Why is a strong smell added to the gas that heats our homes?
63. Why do towns have water towers?
64. How does a skyscraper push tap water up hundreds of feet?
65. How does cold water from Lake Ontario cool Toronto's downtown buildings?
66. How does a 911 call get help to the right place?
67. How do hospitals keep running during a power outage?
68. What is under a city street?
69. How do crews fix pipes without digging up the whole street?
70. Why are old city pipes replaced with new materials?
71. How does a water meter count how much water you use?
72. What are the big orange balls on some power lines?
73. Why do wires sag between poles?
74. Why don't drains make your bathroom smell like the sewer?
75. How do pumps push water uphill?

Expedition 4: Wild Neighbors & Green Spaces

76. Why do raccoons do so well in cities?
77. Why do coyotes live in some cities?
78. Why do peregrine falcons nest on skyscrapers?
79. Why are there so many pigeons in cities?
80. How do common nighthawks nest on city rooftops?
81. Why do city birds sing at a higher pitch?
82. How did crows in Japan learn to use traffic lights to crack nuts?
83. Why do Canada geese stay in city parks all year?
84. What tiny creatures live on a city sidewalk?
85. Why do rats live near people, and how can we keep them away?
86. What should you do if you meet a wild animal in the city?
87. What is a green roof, and how does it help?
88. Why do cities plant trees along streets?
89. How do trees survive in tiny squares of dirt in the sidewalk?
90. Why do cities plant many different kinds of trees?
91. Why do some cities turn empty lots into community gardens?
92. Why do cities need parks?
93. Why does Toronto have so many hidden forest valleys?
94. How can plants grow up the side of a building?
95. Why do some parking lots let rainwater soak through?
96. Why can lichens tell scientists about a city's air?
97. How do animals cross busy roads safely?
98. Why are some city lawns turning into wildflower meadows?
99. How can you find the age of a city tree?
100. How can you be a city nature detective?

Expedition 5: Lights, Noise, Air & Trash

101. How does bright night light change the lives of birds and insects?
102. What are "lights out" programs for migrating birds?
103. Why are cities switching to LED streetlights with warmer colors?
104. How do smart streetlights know when to dim?
105. Why are cities so noisy?
106. Why do cities have quiet hours and noise rules?
107. How do walls along highways block noise?
108. How do thick windows keep city noise out?
109. What is a soundscape, and how can you listen to one?
110. What is smog?
111. Where does city air pollution come from?
112. How do scientists measure the quality of the air?
113. Why can smoke from faraway wildfires reach a city?
114. How does a garbage truck squeeze in so much trash?
115. Why do aluminum cans jump off a belt at the recycling plant?
116. What is a modern landfill like?
117. Why can't everything go in the blue bin?
118. How does a city turn green-bin scraps into compost and energy?
119. Why does a plastic bottle left outside last for hundreds of years?
120. How do street sweepers clean the road?
121. How do snowplows and salt trucks clear the road?
122. Why is too much road salt a problem?
123. What should happen to old phones and computers?
124. How can a neighborhood make less trash?
125. Why does a school bus flash its lights and swing out a stop sign?

Expedition 6: How Cities Grow & Get Planned

126. What did the very first cities look like?
127. How did ancient Romans bring water to their cities?
128. How did elevators and cars change the way cities grew?
129. Why do some cities have a grid of streets and others wind around?
130. What do city planners do?
131. What is a zoning map?
132. How do planners decide where a new school or park should go?
133. What is population density?
134. How do map layers help planners?
135. What is the difference between a city growing up and growing out?
136. Why do cities protect old buildings?
137. How do cities get ready for heavy storms and floods?
138. What helps a city stay cool during a heat wave?
139. What makes a city a good place for kids?
140. What is a smart city?
141. How do bike-share systems work?
142. How can kids help design their city?
143. How do planners test a city design before it's built?
144. Why do some cities leave a ring of green land around them?
145. Why do neighborhoods in the same city feel so different?
146. Why do cities have public art?
147. How do cities make streets easier for everyone to use?
148. Why do so many people in cities live in apartments?
149. How will today's kids shape the cities of tomorrow?
150. How do all the city systems fit together like one giant machine?