6. Experts think the builders used simple , such as levers and ramps.
7. What was the most dangerous project.
8. It lets ships pass the Atlantic and Pacific oceans.
9. However, the was too difficult and they stopped.
10. The total of people worked on the canal.
11. That means it was very hot and , with about 105 inches, 267 centimeters, of rain a year.
12. In , an oil company found the largest oil field in North America.
13. The Alaska Pipeline is the pipeline in the world.
14. It crosses three mountain and more than 800 rivers and streams.
15. It is about 20,300 miles, 32,670 kilometers, and it is the longest in the world.
This is the audio script:
Humans are great builders.
Examples are all over the world.
The Egyptian pyramids, the Panama Canal,
and the Alaska pipeline are just a few.
Thousands of people worked on these enormous structures.
What makes these structures such amazing achievements?
Is it their size? Is it their beauty?
Is it the number of workers? Is it the danger of the work?
The ancient pyramids of Egypt are still a mystery today.
No one knows exactly how the Egyptians built them.
The biggest pyramid is the great pyramid of Giza.
The Egyptians built it in about 2550 BCE.
The workers used 2.5 million limestone blocks.
The great pyramid covers 123 acres, 50 hectares,
or 500,000 square meters.
It's 480 feet, 146 meters high.
The sides are 755 feet, 230 meters long.
How did the workers build the great pyramid?
There were no wheels at the time, so there were no cranes or pulleys.
Experts think the builders used simple machines, such as levers and ramps.
The great pyramid took over 80 years to build.
Approximately 30,000 people worked on it.
What was the most dangerous engineering project?
It was the Panama Canal.
This waterway in Central America is 50 miles, 80 kilometers long.
It lets ships pass between the Atlantic and Pacific oceans.
The French started the project in 1881.
However, the work was too difficult and they stopped.
The United States continued the project in 1904 and completed it in 1914.
A total of 56,307 people worked on the canal.
The area around the canal was very dangerous.
It had a tropical climate.
That means it was very hot and wet, with about 105 inches, 267 centimeters, of rain a year.
The heavy rain often flooded the rivers.
There were mosquitoes.
No one knew that mosquitoes caused malaria.
Thousands of workers died from malaria and accidents.
One of the greatest engineering achievements of the 20th century was the Alaska Pipeline.
In 1968, an oil company found the largest oil field in North America.
How could they get oil from Alaska to the rest of the United States?
They worked with other oil companies to build a pipeline.
The Alaska Pipeline is the longest pipeline in the world.
It carries oil for 800 miles, 1,287 kilometers, through the cold hard Alaskan wilderness.
It crosses three mountain ranges and more than 800 rivers and streams.
More than 70,000 workers built it.
They worked for nine years in sub-zero temperatures.
They completed the work in 1977.
Since then, over 15 billion barrels of oil have traveled through the pipeline.
There are many other amazing engineering projects around the world.
For example, the Great Wall of China was the largest building project in history.
The Great Wall is approximately 4,500 miles, 7,242 kilometers long.
Another example is the Pan-American Highway.
It is about 20,300 miles, 32,670 kilometers, and it is the longest road in the world.
It goes through Canada, the United States, Mexico, Central America, and South America.
Can you think of other examples of great engineering projects?
Which project do you think is the greatest of all?
This is the end of the audio program.
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