[PBS Intro] A long time ago a guy built a tomb out of rocks so he could live in it after he died and not be dead.

His son was like "Hey that's cool" so he built one too.. Then his son was like "Me too" so he made a third and they were all buried there.

And that's how we got this.

The pyramids of Giza.

How did people who hadn't even invented the wheel build these things, and... why?

They're so big!

They're so precise!

They're so directionally oriented!

They're so mysterrrrrrious.

At first glance they really do look out-of-this world.

Thing is, the pyramids are much older than you probably think.

They were already ancient history to people IN ancient history, which led to some pretty wild theories about how they came to be.

But pyramid technology didn't just show up out of nowhere.

It was the end product of centuries of scientific and cultural evolution, of people... figuring it out.

And it definitely wasn't aliens.

[OPEN] Early on, Egyptians buried their dead like we do.

The desert naturally mummified some corpses, which influenced their religious beliefs: You need to preserve the body to reach the afterlife, and when you get there you'll need all your stuff.

Rich people's graves had nicer stuff, and they needed to protect their afterlife investment.

First with simple mounds, and later with mud brick "eternal houses".

Then a king named Djoser was like "Why have one little mud mastaba when I can have six stone mastabas in a stack?"

so he stacked six stone mastabas like a mastaba boss and the age of the pyramids had begun.

This was literally the first time humans had piled stone this high.

Egyptians knew totally vertical walls got less stable as they got taller, so Djoser's architect stacked bricks at an incline and let gravity do the work.

Step pyramid achieved!

Why pyramids and not other shapes?

If you want to make a big pile of blocks, a pyramid gets you the most stability for the least material.

A third of the way up, you've already laid two-thirds of your stone.

Halfway, you've placed more than 80%.

Next comes Sneferu, Mr. Pyramid.

He built his own step pyramid, but then decided he wanted a smooth one instead, so they started on a second.

No one had ever built one of those before, so they made some mistakes.

For starters, they built it on sand, which is soft, they laid blocks carelessly, and it was too steep, so halfway through they changed the slope and ended up with this.

Sneferu was like "you're not burying me in that", so he ordered a third pyramid!

Only this time they built a solid foundation, laid the stones in horizontal rows, and precision cut the edges.

Sneferu's motto?

If at first you don't succeed, try again, and then try again one more time.

Sneferu had experimented his way to a blueprint for building awesome pyramids The Great Pyramid at Giza, built by his son Khufu, took that blueprint to the next level.

Khufu's pyramid remained the tallest structure on Earth for almost 4000 years, until some church tower in the year 1311, which fell down, so it was tallest again until this radio antenna was finished in 1889.

Khufu's son Khafre built his pyramid right next to dad's, and he didn't stop innovating.

Instead of leveling the entire 46,000 square meter footprint, he built his pyramid over a natural stone mound and only leveled the outer edge, which was less work, duh!

It's 3 meters shorter than his dad's, but this higher ground creates the illusion that Khafre's pyramid is taller.

Kids, amirite?

But even these seemingly perfect pyramids weren't without mistakes.

Khafre's had a slight twist near the top in order to make the edges line up evenly.

What's remarkable is Egypt's biggest stone pyramids were the product of just three human generations, but those were generations full of trial and error.

Pyramid building continued for nearly 700 years, and like any product, efficiency started to win out over quality.

Precision-cut cores were replaced by rough-cut blocks.

Kings still wrapped their pyramids in fine white limestone, but over the next thousand years that was removed by stone stealers and rock robbers, leaving the cheaply-produced cores to collapse into rubble, which is probably why you've never heard of them.

Ironically, the kings were probably disappointed by the whole afterlife thing, but the pyramids themselves have proven to be surprisingly resilient.

Ancient is not a synonym for stupid.

The world's first skyscrapers were tombs, and just like our own buildings, they didn't spring up out of nowhere, they were the product of centuries of engineering trial and error.

Go back 500 years and show someone a smartphone and they'd probably think you were a wizard.

But when we look back from the present at the ideas and failures along the way, we see that it's not magic at all!

It's science.

And if you still think aliens did it, you're in de-Nile.

You know, the river.

Stay curious.