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hey smart people so a few weeks ago we
made a video about the pyramids and how
while they are pretty heck and
impressive we can trace the evolution of
their construction and see the ancient
Egyptians using trial and error even
making a few mistakes which basically
tells us they didn't need aliens to
build them they just needed science you
guys really like that video but a few of
you were a little bothered that despite
the fact it was called who built the
pyramids I didn't talk about how the
pyramids were made so let's talk about
it 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 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 basis level less than
2 centimeters it's square within 11 and
its edges are aligned to the compass
within 3 sixtieths of a degree this
precision is pretty incredible since
compasses didn't actually exist yet and
since 4,500 years ago then 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-degree 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 could make a
right angle you can make a level put
that on some legs and you can even 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
Pyramids core is made of more than 2
million blocks of rough yellow
I'm stone this is quarried right next to
the pyramids which is a big reason why
they chose sites like Giza where
prehistoric oceans have deposited this
building material right under their feet
they would dig channels and pry these
blocks right from the earth besides in
the walks 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 these pyramids were originally
covered in smooth white limestone from
quarries up the Nile which was stolen
using other buildings thousands of years
ago we found many chisels drills and
songs 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 pools 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 calculate this amount of stone
can be cut and moved by a quarry team of
12 to 1500 workers which is totally
doable heavier stones like the granite
using the pyramids 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 just
a few centimetres but then again they
didn't have Twitter to distract them
we found Egyptian boats large enough to
have floated these stones down the Nile
but how are 2 million blocks actually
moved into place it might be hard to
believe but wheels for transportation
are a surprisingly recent invention not
because making a round thing roll is
hard to figure out but because inventing
a workable axle is the oldest known
rolling wheels on earth dated 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
burying wood rails horizontally
will allow us led to slide more freely
but researchers at the University of
Amsterdam showed in 2014 that sand has
an interesting property wetting what the
right amount of water it makes it
remarkably slick a team of 10 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 to constructing
ramps to deliver stone it 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 that 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 believed the Egyptians
extended a big wide ramp near the bottom
where a pyramid requires most of its
stone and then spiral ramps near the top
where fewer blocks were needed wooden
letters 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 in 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 movies
Egyptologists like mark Lehner have
uncovered enormous cities built to feed
house and equipped thousands of skilled
workers with breweries bakeries tool
shops signs that whole families live
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
now this is science and you shouldn't
just take my word for it I put links to
some awesome research about pyramid
engineering down in the description so
check it out for yourself and if you
have other ideas let me know in the
comments
just remember bring some evidence I'd
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