This episode is supported by Skillshare. Hey smart people, so a few weeks ago we made
a video about the pyramids, and how, while they are pretty heckin’ impressive, we can
trace the evolution of their construction and see the ancient Egyptians using trial
and error, and even making a few mistakes, which basically tells us they didn’t need
aliens to build them, they just needed science. You guys really liked that video, but a few
of you were… a little bothered that, despite the fact it was called “WHO built the pyramids?”
that I didn’t talk about HOW the pyramids were made. Soooo, let’s talk about it! [OPEN] The hundred-plus pyramids scattered around
Egypt were all built a bit differently, but we’re gonna focus on THE BIG ONE. Let’s review the stats! The Great Pyramid originally rose more than
146 meters tall and contained about 2.3 million stone blocks. But the start of any construction project
truly begins with the foundation, which is impressive in its own right. Its base is level to less than 2 cm, it’s
square to within 11 (cm), and its edges are aligned to the compass within 3/60ths of a
degree. This precision is pretty incredible since
compasses didn’t actually exist yet, and since forty-five hundred years ago the North
Star was in a completely different place. But finding North is actually pretty easy,
just watch where any star rises and sets during the night, and cut the angle in half. After that, squaring the sides just requires
measuring a right angle. Pythagoras and his equation came way later,
but ancient cultures like the Egyptians knew a 3-4-5 triangle made a 90˚ corner. They could even make a right angle with two
circles: the line connecting the intersection of the arcs is perpendicular to a line through
their centers. To level the base, some theories say the Egyptians
used water filled channels as natural levels, but this isn’t likely when you consider
how much water they’d have to carry in to keep it from evaporating. But if you can make a right angle, you can
make a level. Put that on some legs, and you can level over
long distances. When you think about it, a pyramid is just
a bunch of stacked squares, so if you can master this measurement, you’re most of
the way there. Now we just need some stones. The Great Pyramid’s core is made of more
than 2 million blocks of rough yellow limestone. This was quarried right next to the pyramids,
which is a big reason why they chose sites like Giza, where prehistoric oceans had deposited
this building material right under their feet. They would dig channels and pry these blocks
right from the Earth, and the size of the blocks was actually determined by the natural
thickness of these limestone layers. You can see evidence of these layers in The
Sphinx, which was actually dug out of the Earth, not built on top of it. The pyramids were originally covered in smooth
white limestone from quarries up the Nile, which was stolen to use in other buildings
thousands of years ago. We’ve found many chisels, drills, and saws
used at these quarries, and the only metal Egyptians had access to was copper. That’s a pretty soft metal, but when a slurry
of sand and powdered rock is poured in as an abrasive, even copper tools can cut limestone. To build the Great Pyramid in 23 years, an
Olympic swimming pool’s worth of stone had to be quarried every eight days. That’s a lot, but modern pyramid building
experiments using technology available to Ancient Egyptians calculated this amount of
stone could be cut and moved by a quarry team of 1200 to 1500 workers, which is totally
doable. Heavier stones, like the granite used in the
pyramid’s inner chambers, are much harder than limestone. They were literally chipped out by hand using
heavy dolerite hammer stones, which we’ve also found… a LOT of. It would have taken a full day’s pounding
to chip away a few centimeters, but then again they didn’t have Twitter to distract them. We’ve found Egyptian boats large enough
to have floated these stones down the Nile, but how were 2 million blocks actually moved
into place? It might be hard to believe, but wheels for
transportation are a surprisingly recent invention. Not because rolling a round thing is hard
to figure out but because inventing a workable axle is. The oldest known rolling wheels on Earth date
to before the Great Pyramid, but not in Egypt. Paintings tell us Egyptians used wooden sleds
to move large objects, but they still had to deal with friction. Burying wood rails horizontally will allow
a sled to slide more freely, but researchers at the University of Amsterdam showed in 2014
that sand has an interesting property, wetting it with the right amount of water makes it
remarkably slick. A team of ten workers can easily pull a one-ton
sled, but people always seem to forget that Egyptians had animals like donkeys and cattle
around to help too. Constructing ramps to deliver stone must have
been nearly as monumental as the pyramid itself. This is one place where there’s no records
of what they looked like, but researchers have examined lots of possibilities. An engineer named Craig Smith has done probably
the most detailed ramp analysis, calculating how many stones could be delivered with each
design, and he believes the Egyptians extended a big, wide ramp near the bottom where a pyramid
requires most of its stones, and spiral ramps near the top where fewer blocks are needed. Wooden levers, and round dolerite “ball
bearings” were used to guide stones into place, where they were carved to an exact
fit. Joints between some of the few remaining smooth
outer stones are so precise you can’t even slip a credit card between them, but digs
have shown they weren’t as careful with interior stones. It’s a popular idea that the pyramids were
built by slaves, but you shouldn’t believe everything you see in the movies. Egyptologists like Mark Lehner have uncovered
enormous cities built to feed, house, and equip thousands of skilled workers, with breweries,
bakeries, tool shops… signs that whole families lived nearby. Egyptian society at all levels dedicated themselves
to what they viewed as the kingdom’s proudest work. It’s actually pretty incredible that we
have as much evidence as we DO about how the pyramids were built, but that doesn’t mean
building them was easy. In fact it’s the opposite. But difficult doesn’t mean impossible. Stay curious.
Disappointing. Despite the title there is very little science in this, just the usual speculation with little evidence to back it up. No I don't have the answers nor would I propose aliens (a nice straw man they included) but their theories on using wet sand to aid in cutting and moving the giant blocks have failed in practical tests even on a small scale. Theres also no evidence for the ramp theory, it just sounds generally reasonable. They also mention the precise measurements required without explaining them.
One part that sounded interesting is he claimed we have a record of the trial and error as they learned to build pyramids - however instead if giving evidence for this he says we'll just examine the great pyramid. This, if true, Id like to hear more about.
lot of what if here
When he opened with "Hey smart people" i closed the tab.