1- Hi, it's Doug.
2Have you ever played the game Jenga?
3Some people are able to build some pretty tall towers.
4Like, check out this, the world record.
5This person piled 485 blocks on one single Jenga block.
6That's some amazing balancing skills.
7Someone named Ashley has a question about building things.
8Let's give Ashley a call now.
9- Hi, Doug.
10- Hi, Ashley!
11- I have a question for you.
12What's the tallest skyscraper anyone can build?
13- Oh, that's a great question.
14Humans have been trying to build super tall things for a long time.
15Before skyscrapers were invented, pyramids were the tallest objects built on earth.
16Take a look at this one. It's called the Great Pyramid of Giza.
17Builders stacked over 2 million heavy stone blocks to make it that high.
18The pyramid was the tallest human-made thing on earth for almost 4,000 years,
19until this came along.
20This is the Lincoln Cathedral,
21and it was once over 500 feet tall,
22but then, something happened.
23If you've ever built a tower with blocks, you've probably noticed that the taller you build, the harder it gets,
24and that's what happened to the Lincoln Cathedral.
25The tallest part toppled over during a storm.
26It was just too tall.
27When it was built, people just couldn't build things that were very tall yet.
28Before I go on, I'm curious,
29why couldn't those earlier pyramids and cathedrals be built as high as skyscrapers are today?
30What do you think?
31Well, I'm not sure how you answered,
32but you might think that the earlier buildings weren't made of very strong materials,
33but that's not really what's most important.
34Bricks and stone blocks are incredibly strong.
35It turns out, it's the piling up of bricks or stone blocks that creates the problem.
36You see, buildings back then were made by piling bricks or stones on top of each other.
37The taller the building, the more bricks they would use,
38and the more bricks they would use, the heavier the building would get.
39If it got too heavy, it could collapse from its own weight,
40or, it could topple over.
41So the piling up of bricks or stone blocks is what kept people from making really tall buildings.
42Since then, we've figured out how to build even taller buildings,
43buildings that are way taller than the first pyramids and cathedrals,
44buildings that seem to scrape the sky.
45These buildings, called skyscrapers, are now the tallest human-made objects on earth,
46and they don't fall down!
47How is that even possible?
48Well, building a skyscraper involves a totally different way of creating a building.
49Rather than stacking up building blocks, the way they did with pyramids or the way you do in Jenga,
50it involves giving the building a skeleton, or structure, on the inside.
51This new way of building led to the first-ever skyscraper,
52the Home Insurance Building in Chicago.
53Instead of building with piled-up bricks, it was built with a steel skeleton,
54and since the skeleton was holding the building up,
55the rest of the building, like walls and windows, could be hung on the steel beams,
56like pictures hang on walls.
57And since those walls didn't need to be made out of piled-up bricks anymore,
58they could be really light,
59at least much less heavy than building materials of the past.
60This changed everything.
61By building with steel skeletons instead of heavy bricks,
62builders could build taller than ever.
63Now, even with a skeleton, there was another thing that could knock it over, wind.
64A skyscraper is like a giant sail.
65The taller it is, the more wind pushes into it,
66and those winds can actually knock a skyscraper down.
67So, skyscraper builders are constantly trying to find ways to get around this problem,
68like the builders of this skyscraper did.
69This is one of the tallest skyscrapers in the world.
70You see the shape of the sides?
71Why do you think they built it this way?
72It's all because of the wind.
73The spiral shape helps the wind twist around it instead of crashing into it.
74And take a look at this one.
75You notice the top?
76Some skyscrapers are even built with holes in them so that the wind blows straight through.
77Now, by inventing new ways to trick the wind,
78we've been able to build from 88 floors, to 101 floors,
79to the tallest skyscraper in the world, currently the Burj Khalifa.
80It's 163 floors tall.
81And that brings us back to our question,
82how tall can a skyscraper be?
83Well, no one really knows for sure how tall, but we are sure of this:
84we can build a lot higher than the skyscrapers we have today.
85In fact, builders in Japan are planning to build a skyscraper that's one mile tall.
86It's called the Sky Mile Tower,
87and when it's finished, it will be more than 10 times the height of the Great Pyramid of Giza.
88That's twice as tall as the tallest skyscraper we have now.
89That's all for this week's question.
90Thanks Ashley, for asking it.