00:00Secant Cosine Tangent Sine 3.14159 Yeah, that was the cheer we heard coming from
00:07the trigonometry club back in the day.
00:10For the rest of us in math class, terms such as sine, tangent, and pi were just bewildering.
00:17Who invented these, and why?
00:19Was their only purpose to make it harder for students?
00:23Well, not quite.
00:25Trigonometry was invented by the ancient Egyptians.
00:28They needed this knowledge to construct pyramids, and they did a pretty good job too.
00:33The Great Pyramid in Giza still stands today, some 4,500 years after it was built.
00:39No recalls either.
00:41So let's get out of that classroom and on a journey through time to reveal the secrets
00:46behind the ancient Egyptians' precision.
00:49Here you are, standing on the Great Pyramid's construction site, some 9 miles from Cairo.
00:55The city still isn't there, as you're surrounded only by the desert and teams of
00:59construction workers.
01:01They're transporting large stone blocks weighing 2.5 tons each.
01:05They're inside a wooden sled that sits on large rollers.
01:09A crew of 8 men rolls these blocks along the ground.
01:13You immediately think of the rollers on a supermarket cash register.
01:18The principle is exactly the same, but the scale is greater, much greater.
01:23Scientists estimate that the Egyptians used 2.3 million such blocks in the Great Pyramid
01:28alone.
01:30And the block in front of you is one of the lighter ones.
01:33The heaviest of them weighed up to 15 tons.
01:36But where did all these blocks come from?
01:39Most of them originated from quarries around Giza.
01:42It's not that impressive, you think.
01:44But wait until you hear how ancient engineers transported the granite used in construction
01:51over 500 miles to the pyramid.
01:54There were no railways or highways back then, but the mighty Nile was always there.
02:00Researchers even believe that the Egyptians dug a canal to connect the Nile directly to
02:05the pyramid's construction site.
02:07All they had to do then was to wait for the flood season to begin, and voila!
02:12The rising water levels floated the heavy stone blocks for them.
02:16But how did they lift the enormous stones on dry land to stack them up to the top?
02:22Did they use oversized cranes?
02:24Well ancient Egyptians worked around this problem, literally speaking.
02:29One of the workers is now pointing to the giant ramp going around the pyramid they're
02:33building.
02:34This is how a mountain road zigzags its way to the top.
02:38If the ramp went directly to the top of the pyramid, then workers couldn't pull the
02:42stone blocks along it.
02:44It would be too steep.
02:46Scientists have calculated that 8% could be the maximum incline.
02:50So ancient Egyptians just extended the ramp around the pyramid.
02:55Again, these are all theories, as the ramp could've been inside the pyramid, as some
03:00researchers suggest.
03:02The exact building method is still a mystery, guarded by the Sphinx.
03:05That's its real name, right?
03:08Wrong.
03:09As the Great Sphinx is just the statue's alias.
03:12You know, the name writers take when they want to hide their true identity.
03:16Or a singer's stage name.
03:18The Sphinx's real name, translated from Egyptian, means Horus in the horizon.
03:24That was the name for the Egyptian deity of the sky.
03:27The trail of mystery doesn't end there.
03:29As a man walks past you with a bucket of paint, he's going to add a touch of color to the
03:34Great Sphinx.
03:36Researchers found specks of this red color next to its ear.
03:40That was some strong paint, as it survived for thousands of years.
03:44You are now standing straight in front of the Sphinx.
03:47You look up.
03:48It's very tall, right?
03:5066 feet to be precise.
03:52Now resist the urge to take a selfie.
03:54You can do it!
03:56Now you notice something else.
03:58It looks like the Sphinx is in the center of a giant triangle in the back.
04:02That's one side of the Great Pyramid.
04:05And no, your eyes are not playing tricks on you.
04:07The Sphinx really does sit in the center of the pyramid's lateral face.
04:12Here's where math comes in handy.
04:14A pyramid has four sides, called lateral faces.
04:18There's also a fifth face, the base.
04:21But that's not visible.
04:22It's, wait for it, face down!
04:26The Sphinx has one last mystery to reveal – its age.
04:30Scientists agree that Pharaoh Khafre built the Sphinx.
04:34He ruled after his father, who had built a Great Pyramid nearby.
04:38So both structures were finished around the same time.
04:41Let's talk about numbers again.
04:43You've heard of Cleopatra, the Egyptian princess described as a woman of great beauty?
04:49She saw the pyramids, but she lived closer to the time of the first iPhone than the time
04:54of the people who built the pyramids.
04:57Fascinating, right?
04:58You can see thousands of people around you.
05:01They're working hard to build the Pharaoh's tomb.
05:04But how many of them are there exactly?
05:06One Greek philosopher estimated there were as many as 100,000 workers.
05:12Seems like an okay number for such an enormous structure.
05:15But it can't be true.
05:17Science simply can't back up this number.
05:20Egyptologists put the total number of workers at 30,000.
05:24And yes, Indiana Jones was one of them, at least on the big screen.
05:28But he showed up late.
05:30Egyptologists know a lot about the pyramids, but not everything.
05:34Not because they don't want to, but because they haven't yet dug up enough evidence.
05:40They can only guess how the building process went.
05:44First engineers would arrive to choose the right spot and do the necessary measurements.
05:49That's why they needed all that complicated math.
05:52Then it's time for sourcing the material, the large stone blocks I mentioned earlier.
05:57When boats deliver them to the site of the future pyramid, workers can finally do their
06:02thing.
06:03They operated in smaller groups, but there were at least 2,000 of them chiseling and
06:09carving away at any given time.
06:11Sounds like a typical construction site today.
06:14Well, that's because it is, just thousands of years ago.
06:17It's amazing what ancient Egyptians were able to achieve with just copper and stone
06:22tools.
06:24The pyramid is now complete in front of you.
06:27But is it the same pyramid we see today?
06:29Why is this structure shining bright in the desert sun?
06:33Isn't it supposed to be a dusty yellow color?
06:36Well, no.
06:37Human activity and the elements have completely stripped the outer layer of stones over time.
06:43Expert craftspeople polished these blocks using nothing but stone and sand.
06:48The end result was a smooth and shiny rock.
06:51On the day it was completed, the Great Pyramid of Giza was a perfect triangle of light.
06:57Its polished sides acted like giant mirrors, reflecting the powerful Egyptian sun.
07:02This is the point where you should put your glasses on.
07:04And that shiny thing you see at the pyramid's very top is actually gold.
07:09The capstone at the top of the pyramid is called a pyramidion.
07:14It was covered in sheets of gold.
07:16As you can guess, these were the first stones to disappear.
07:19Let's make another stop before we get you back to your classroom.
07:23We travel to the British Isles, and no, Stonehenge isn't our destination.
07:28It is Newgrange in County Meath.
07:31Scientists estimate that the ancient peoples of Ireland built this stone monument around
07:36the year 3200 BCE.
07:39This makes it older than both Stonehenge and the Great Pyramid in Giza.
07:44The function of the circular mound in Newgrange is the same as the one of the Great Pyramid
07:49and equally mysterious.
07:51The estimated amount of loose stone present in the valley is over 220,000 tons.
07:58And it's not just randomly thrown on a pile.
08:01The order in which the stones are set makes the structure water-resistant.
08:06That would explain how Newgrange had survived for so long.
08:10Kinda makes you want to splash out the cash for that waterproof phone case, huh?
08:14Well, you're back in your school desk, but today's math lecture is the last thing on
08:19your mind.
08:20You're thinking about how great the Egyptian pyramids are, and if we have something similar
08:25today.
08:26It turns out modern engineers are just as impressed with the Great Pyramid as you are.
08:31There's a glass pyramid sitting in the main courtyard of the famous Louvre Museum in Paris.
08:37The panorama of San Francisco wouldn't be complete without the 48-story Transamerica
08:43Pyramid.
08:44But Las Vegas went the furthest.
08:47There we find the Luxor Hotel.
08:49It's so big that it's the third-largest pyramid on the planet.
08:53And guess what's in front of it?
08:55Yep, a replica of the Sphinx.
08:57It's 110 feet tall, two stories higher than the one in Giza.
09:02Yeah, everything's bigger in Vegas.
09:05That's it for today, so hey, if you pacified your curiosity, then give the video a like
09:09and share it with your friends.
09:11Or if you want more, just click on these videos and stay on the Bright Side!
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