Supersized Earth is a BBC programme that explores the way we have redesigned our planet to build the modern world.
Dallas Campbell, the show's host, goes up to the world's tallest building, the Burj Khalifa in Dubai, which has the world's highest windows. He joins the team whose job is to clean them.
Watch the four-minute video clip and answer the questions about it.
The activity is suitable for Intermediate students.
1 How far below is the next platform?
2 What would happen if Derek dropped anything?
3 What two factors are really important to build buildings this high?
4 What is the main danger for tall buildings?
5 Can you explain what 'confusing the wind' is?
6 How long does it take to clean all the windows?
7 How many windows are there?
To check your answer you can read the transcript below. Remember you can double click on any word to find out its meaning.
Today, I’m going to join the team whose job it is to clean the outside of the world’s highest windows.
Just pull a little slack free. Just pull up on this one. A little bit more.
Okay, now lock the handle off.
Okay. Okay, just lean back, just lean back. You’re okay, you can’t go anywhere.
I need the bucket.
Yeah, hang on a second. Take this…
Do you get nervous at all?
Yes. Scared – little bit scared? Yeah. I haven’t looked down yet. Now I’ve looked down!
It’s almost inconceivable how high these windows are. I’m 60 meters above the next platform below, which is, in itself, 600 meters above the ground higher than the previous world’s tallest building. At this height, if I dropped anything, it could do serious damage.
Building height, is a load of factors you’ve got to take into consideration. One of them obviously is gravity, which I’m feeling right now. The thing about gravity is it’s very predictable. It’s a force that’s going one way. The thing you’ve really got to worry about is wind, because by its very nature it’s unpredictable, it swirls around and it can affect the building, as well as window cleaners.
Surprisingly, very tall buildings aren’t in danger of being blown over, but of being sucked over. As wind hits them, it can form small whirlwinds, called vortices. This swirling air can create low-pressure areas that tug at the building. And if enough of them combine up the tall straight sides, they could make the tower rock from side to side. So why doesn’t this happen to the Burj Khalifa? Well, it’s taken some careful aerodynamic design. By stepping the building in as it rises and introducing angles and curves, the Burj Khalifa breaks up the desert wind, preventing the vortices from combining dangerously. The designers call it ‘confusing the wind’, and they reckon it’s the only way to build this high.
It strikes me, being out here, that even though we are in such a technically advanced building, that – in order to keep it nice and clean, you still can’t beat a man with a squeegee and a bucket. It takes three months to clean all 24,000 windows, and when they finished, the team has to start all over again.
If you are going to build a building that’s truly iconic, you’ve got to make it look nice.
And keep it looking nice!
And keep it looking nice, exactly, yeah.
Keep going, you’re all right. Keep going, lovely.
Wow, that was intense! I don’t know how those guys do it every day. That was intense, but good.