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00:02The Lighthouse of Alexandria, one of the ancient seven wonders.
00:08The world's tallest stone tower for over 1,500 years.
00:12It's an engineering marvel.
00:14Build a skyscraper from stone.
00:17You're crazy, you know, we don't do that.
00:20Once a shining beacon to the greatest city in ancient Egypt,
00:25today the lighthouse is lost in time.
00:28We are actually discovering for the first time
00:31one of the wonders of the ancient world.
00:34Now investigators use innovative underwater digital scanning technology
00:39to uncover the hidden secrets of the vanished lighthouse.
00:45They recreate ancient engineering techniques
00:48to reveal the lost skills of the civilization that built it.
00:56We're going to be able to do it.
00:57Yeah, it's funny, it's funny.
00:58We set fall to it.
01:01To solve the mysteries of this ancient wonder,
01:05we'll unearth its sunken ruins.
01:09We'll resurrect an ancient weapon of war
01:12and rediscover long-forgotten technology
01:17to rebuild the lighthouse of Alexandria.
01:29Alexandria, the last of ancient Egypt's capitals
01:34is the largest city on the Mediterranean.
01:39Legend has it that in 280 BC,
01:42it's home to a mighty megastructure
01:45that no other ancient city can build.
01:51At the entrance to Alexandria's port
01:54stands the tallest tower in the world,
01:57an Egyptian skyscraper.
02:02Immense bronze tritons, Greek gods,
02:06keep watch over the streets below,
02:09while mirrors beam a blazing light across the sea,
02:12making Alexandria visible to ships still a day's sail away.
02:19Rumors even tell of a deadly weapon at the tower's summit.
02:24Why do the Egyptians build this legendary lighthouse?
02:28And what does it really look like?
02:35The Lighthouse of Alexandria stands for more than 1,500 years
02:42until 1303,
02:45when an earthquake and tsunami send it crashing into the sea.
02:52Today, the lighthouse, along with almost all the ancient city, is gone.
02:59Emad Khalil is a marine archaeologist.
03:02He spent the last 25 years
03:05tracking down ancient Alexandria's lost secrets.
03:11This is the ideal place to start hunting for the lighthouse,
03:16mainly because of the material we have here.
03:20Emad explores the citadel of Kite Bay on Alexandria's waterfront.
03:27Well, this will be the most durable material.
03:30It will withstand the weather and the salt and so on.
03:34And so this probably came from a maritime structure.
03:38It turns out parts of Alexandria's fabled lighthouse survive.
03:43This fortress of Kite Bay was built using some of the blocks that existed in the lighthouse.
03:51And beneath the blocks hides another clue.
03:57Inside the fort stands a sacred mosque.
04:01It should be facing Mecca to the southeast.
04:04But this mosque faces north towards the sea.
04:08A clue that it stands on the old lighthouse foundations.
04:12On the roof of the mosque is a strange octagonal opening.
04:17Can this help Emad work out what the ancient lighthouse looks like?
04:27The structure of this mosque is quite typical until you start looking up.
04:32And this is very unusual.
04:33It's very unusual to have a square minaret, basically,
04:37and part of it is octagonal and then another part is cylindrical.
04:40That doesn't happen in Islamic architecture.
04:45Emad is convinced the mosque's distinctive design,
04:48a square base topped with an octagon and a circle,
04:52copies the shape of the lighthouse.
04:56That's because 30 miles west of Alexandria,
04:59there's an ancient structure that follows this blueprint,
05:03Abu Sir lighthouse.
05:07It stands guard over an ancient necropolis.
05:12So what we have here, basically, is a typical Hellenistic tomb.
05:18An altar in the middle and couches, two couches, one on each side,
05:22one on each side to be used by the visitors.
05:24And then we have the burial chamber.
05:27You can still see the remains and the bones and the remains of the deceased.
05:34On some of the walls, snake carvings offer protection to the spirits of the dead,
05:39typical of a Greek-style burial.
05:44All around us, there are plenty of them.
05:46There are, I think, over 13 of them, very much the same design, Greek tombs.
05:50And this is a building which was built during the same period,
05:53during the same era, in the shape of a lighthouse.
05:57Emad thinks the builders of these tombs and the lighthouse that guards them
06:01take inspiration from the lighthouse of Alexandria.
06:06It's an evidence.
06:07It gives us indication that this is the shape of the original lighthouse of Alexandria.
06:14Abu Sir lighthouse is a miniature copy of the ancient wonder.
06:23Only a few precious images of the lighthouse of Alexandria survive.
06:28And the lighthouse at Abu Sir confirms they offer a true glimpse
06:32of a lost wonder of the ancient world.
06:39So the builders of this were actually able to see the original lighthouse of Alexandria
06:44and copy the design into this structure.
06:49The ancient Alexandria lighthouse had three levels,
06:52a square one, an octagonal one, and a cylindrical one,
06:54very much similar to this monument we have here.
06:59The lighthouse of Abu Sir solves the mystery of the lighthouse of Alexandria's appearance.
07:06It's now clear that it's a huge building with a distinctive three-level design.
07:12But the height of this ancient wonder is still shrouded in legend.
07:19Some say the lighthouse is so tall that a stone falling from its summit would take two days to hit
07:26the ground.
07:29Others that sailors could see the lighthouse beacon up to 300 miles out to sea.
07:39The lighthouse is so tall.
07:40Emod's challenge is to separate fact from fiction.
07:44Can he use archaeological evidence to work out how high the lighthouse of Alexandria soars into the sky?
08:07The lighthouse of Alexandria, one of the seven wonders of the ancient world,
08:12climbs into the sky like no other ancient building.
08:16But just how tall does the lighthouse tower?
08:22Archaeologist Emod Khalil believes Alexandria's eastern harbor holds the answer.
08:31In 1303, an earthquake destroys most of the lighthouse.
08:38But its fallen remains still rest on the sea floor.
08:45What we have here is 13,000 square meters of remains underwater.
08:54Scattered across the seabed lie thousands of stone blocks.
09:01Among them, massive monoliths.
09:06The largest weighing over 70 tons.
09:08The huge blocks pieced together to form the lighthouse door.
09:14A towering gate over 40 feet high and 16 feet across.
09:20Flanking the entrance, colossal statues of Egypt's king and queen, five times taller than a human.
09:28Can this huge door reveal the true height of the lighthouse?
09:39It's a huge puzzle basically and you want to put it back together.
09:44Without a reference, without a picture to base your reconstruction on.
09:49And this is the main challenge of the site.
09:52This mammoth block is a crucial piece of the puzzle.
09:55It will help Emod calculate the lighthouse height.
10:01This huge object, which is about 70 tons in weight, is the right side of the main entrance of the
10:08lighthouse.
10:09The right side of the doorway of the lighthouse.
10:11The angle here is where the wooden door would have fit.
10:17Working out the height of the lighthouse from its broken pieces is tough.
10:24Luckily, an Arab writer from the 14th century offers a helping hand.
10:29He records some of the only reliable measurements of the lighthouse.
10:34He measures the dimensions of its base and the width of the door frame.
10:41In an ancient unit called the span.
10:45Looking at the width of the doorway, of this side of the doorway, we have six feet ten.
10:53And now we can directly relate the actual evidence to the literature sources,
10:59which mention that the measurement would be ten spans.
11:04This recovered block allows Emod to establish that one Alexandrian span equals eight inches.
11:13We can start rebuilding not just the dimensions of the lighthouse, but the entire complex of the lighthouse.
11:21Translating the ancient measurements reveals that the lighthouse stands on a 100-foot square base.
11:29This gives Emod a starting point to estimate the building's height.
11:35He combines Greek principles of proportion and imagery from ancient coins to finally get his result.
11:45We think that it was 300 feet in height.
11:48And so basically it was an ancient skyscraper.
11:52Nothing like this in the ancient world.
11:56The lighthouse of Alexandria soars higher than any other stone tower in the ancient world.
12:02And even the first 20th century skyscrapers.
12:06Why does it need to stand so tall?
12:22The lighthouse of Alexandria, one of the seven wonders of the ancient world.
12:27At over 300 feet, it stands taller than any stone tower until the 20th century.
12:35A lighthouse must shine far and bright to warn sailors away from dangerous waters.
12:42But even the tallest lighthouse in America, Cape Hatteras Light in North Carolina, stands just over 200 feet tall.
12:51So why is the ancient lighthouse of Alexandria over 100 feet taller?
12:56Could this be so it can guide ships along the treacherous waters leading up to Alexandria?
13:05A clue lies 130 miles west of Alexandria, off Egypt's Mediterranean coast, at Marsa Bagush.
13:17Beneath the calm surface lurk deadly rocks and shifting sandbars the size of houses.
13:25Half buried in the sand lie the shattered remains of countless amphora.
13:31Ancient clay pots for carrying wine and oil.
13:36These shards span 2,000 years of history.
13:41And hint, this bay is a ship's graveyard.
13:45Is the colossal lighthouse at Alexandria built to prevent endless shipwrecks?
13:54Archaeologist Emad Khalil and his team dive this site to investigate if these broken pots are evidence of ancient wrecks.
14:03They find undisturbed amphora on every descent to the sea floor.
14:10During diving we just came across some shards of pottery inside the bay.
14:14And the further we look, we discover more pottery, more ceramic.
14:19And then we started discovering single amphora, intact amphora.
14:25In Emad's search for evidence of wrecked ships, the intact amphora are a puzzle.
14:32Finding an amphora or few amphoras does not definitely indicate an existence of a shipwreck.
14:39Because amphoras could have fallen off a ship, thrown over a ship.
14:43To find shipwrecks and help explain the height of Alexandria's lighthouse, Emad must investigate further.
14:51The team takes thousands of high-resolution photos to build a digital model of the seabed.
15:01The scan reveals a surprising clue.
15:05The distinct forms of anchors from ancient ships.
15:11But finding an anchor is something else, because anchors do not fall off ships.
15:16The team discovers a total of 14 anchors in the bay.
15:21Finding more than one anchor in the same place means that this has been used frequently by ships.
15:27Marsa Bagouche is an ideal example for a safe haven or a safe natural anchor.
15:32First of all, it's deep enough for ships to come in.
15:35Secondly, the entire bay is protected from both sides by reefs.
15:39So whenever the wind comes from, it's still protected.
15:45The discovery here, not of the shipwrecks, but of a safe haven for ships, transforms Emad's view of the lighthouse
15:53up the coast at Alexandria.
15:56To function as a lighthouse, which is to warn ships against dangerous places for sailing, it does not need to
16:04be 300 feet high at all.
16:07The lighthouse does not need to warn ships of dangers along this coast.
16:13Emad believes ancient ships on their way to Alexandria can navigate safely along Egypt's coast without it.
16:20And Marsa Bagouche is proof.
16:27Half a mile behind the beach dunes, Emad's team makes another discovery.
16:34That reveals why ships anchor here on their voyage to Alexandria.
16:41So what we have here basically is an extensive network of underground wells and cisterns.
16:49This network of tunnels is over 2,000 years old and contains hundreds of thousands of gallons of fresh water.
17:00A life-saving resource for the ancient crews sailing along the northern shore of the Sahara Desert.
17:07Identifying certain spots along the north coast of Egypt that contain fresh water is an excellent advantage.
17:20Marsa Bagouche is one of the most important anchorages on Egypt's coast.
17:24A stopping off point on the shipping lanes into Alexandria.
17:31Ancient sailors in these waters do not need a mega lighthouse in Alexandria to guide them along Egypt's coast.
17:42So is the purpose of the lighthouse to help ships navigate the treacherous approach into Alexandria harbor itself?
17:53Alexandria harbor was described as dangerous to get in because of the series of rocks surrounding the entrance of the
18:00harbor.
18:01If a ship captain was not confident or was not sure where to get in and out from, they might
18:06end wrecking even inside Alexandria harbor.
18:10A tall lighthouse can warn ships away from dangerous shorelines and help them avoid running aground.
18:17But Emad questions if a tall lighthouse helps captains to enter Alexandria harbor.
18:25This lighthouse was an obvious landmark that can be seen from, you know, 50 kilometers out of the sea.
18:30However, getting inside and outside of the harbor in this case, the lighthouse would not be very useful at all.
18:35In this case, you need more detail, more specific reference points.
18:42Fortunately for ancient sailors, the lighthouse isn't the only tall landmark in Alexandria.
18:50The ancient Egyptians carve hundreds of granite blocks into monuments called obelisks.
18:56Two of the most famous are Cleopatra's needles.
19:01Today, these obelisks stand in London and New York.
19:07They are already more than 1,400 years old when Alexandria's rulers move them to their city.
19:16They put up the needles side by side in the center of the harbor, close to the shore, a perfect
19:22landmark for approaching ships.
19:28As long as sailors head straight for the obelisks, their ships are safe from the treacherous reefs lining the port.
19:38A 300-foot-tall lighthouse isn't needed to guide ships into Alexandria.
19:43So why is this structure so tall?
19:48Emad has a surprising theory.
19:51He believes it's not to warn people away, but to draw them into the city.
19:58The lighthouse is a gigantic billboard that announces Alexandria to the world.
20:03It would be a banner, basically, to draw the attention of ships and sailors coming into Egypt.
20:10They would head for this new town.
20:12The new town with this big, huge monument, Alexandria.
20:19The Alexandrians build the lighthouse so audaciously tall to put their city on the map.
20:26Nobody in ancient history ever tried again to build a 300-foot stone tower.
20:33So what are the engineering secrets that allow the lighthouse to stand so tall and for so long?
20:55The lighthouse of Alexandria stands more than 300 feet tall.
21:02New York's Flatiron Building, one of the world's first skyscrapers, is 20 feet shorter.
21:09To build a stone building that is almost like a skyscraper, there has to be some secret that made it
21:15survive for that long.
21:17Structural engineer, Adel Abdel Nabi's day job is to make sure new bridges don't collapse.
21:26But today, he investigates what type of stone Alexandria's engineers use to withstand the extraordinary weight of the lighthouse.
21:37If you ask an engineer if he or she can build a skyscraper from stone, they would think you're crazy.
21:44You know, we don't do that.
21:47Stone is heavy, expensive, and hard to work.
21:52And the higher you build, the higher the risk the building will collapse under its own weight.
22:00But working in the capital of ancient Egypt, Alexandria's stonemasons inherit a 2,500-year-old tradition of building big.
22:11And they have the building know-how to pick just the right stone for the job.
22:17We have Egyptian pyramids. They're built of limestone.
22:21That's structure and material that's taking care of all this mass and weight of the pyramids.
22:26You got the Karnak temple is mainly of sandstone.
22:33Limestone and sandstone, the building blocks of Egypt's ancient megastructures, last for millennia in Egypt's desert air.
22:43Adel investigates if they are tough enough to support a lighthouse over 300 feet tall.
22:51He uses the powerful vice in his lab.
22:54So what this does, it applies a compression force until it crushes the sandstone.
23:02The sandstone holds strong.
23:07Only to shatter at 57,000 pounds.
23:12We're gonna do a crush test for the limestone.
23:17And we're good to go.
23:20The limestone is stronger.
23:27But still shatters at 134,000 pounds.
23:33It looks like neither limestone nor sandstone is strong enough to withstand the natural forces acting on the lighthouse.
23:42For a lighthouse, it's slender buildings.
23:46They get very high stresses.
23:47That's why you needed a strong material to support the building.
23:53With limestone and sandstone both ruled out, Adel tests a third stone in the vice, pink granite.
24:03This is the stone that Egyptian masons used to carve out huge obelisks.
24:10The granite is still going strong when the vice maxes out at over a quarter million pounds.
24:18So you don't have a choice.
24:20The best material to use is granite.
24:23That's the only type of masonry or blocks that can survive these conditions.
24:30Granite blocks are the perfect building material to support the weight of a 300-foot lighthouse.
24:39But how do the lighthouse builders lock the thousands of stone blocks together?
24:45Adel thinks they carefully shape the stones for a perfect fit.
24:53They chisel holes into neighboring blocks and connect them with dowels.
25:00Metal clamps lock the blocks together.
25:03And a special mortar of molten lead fills any remaining gaps
25:08to seal the walls against the raging storms and pounding waves of Alexandria harbor.
25:16But out here, not all dangers come from the sea.
25:23Major earthquakes regularly shake the foundations of Alexandria's buildings.
25:31Are the clamps connecting the lighthouse blocks strong enough to hold out against these monstrous forces?
25:40Adel doesn't think so.
25:43Clamps are not enough to hold these granite blocks together.
25:47It will not give you the resistance you need for these strong earthquake forces.
25:53So how does this super tall stone structure survive earthquakes for over 1500 years?
26:15Alexandria stands in the center of an earthquake hotspot.
26:21Archeologists believe the legendary lighthouse survives 20 major tremors.
26:27Each topping eight on the Richter scale.
26:32Before finally falling into the sea more than 1500 years after its construction.
26:41Even today, earthquakes this powerful wreak total devastation.
26:47The 2008 earthquake in the Chinese Sichuan province hits eight on the Richter scale.
26:53It kills 87,000 people and leaves 5 million homeless.
27:02So how does the lighthouse of Alexandria survive such deadly tremors for over 1500 years?
27:10It could be because the city is home to some of the most brilliant minds in history.
27:19Alexandria's rulers are hungry for knowledge and power.
27:22They make copies of all manuscripts entering the port and put them into the great library of Alexandria.
27:32This vast collection becomes a beacon of intellect that attracts scholars from across the ancient world.
27:40It's here that philosopher Eratosthenes first calculates the circumference of the Earth.
27:50And the celebrated mathematician Euclid first records the fundamental principles of geometry.
27:59The builders of the lighthouse live in a time of rapid scientific innovation.
28:04And the engineering of their stone Goliath is no exception.
28:12Structural engineer Adel Abdel Nabi is about to test an ingenious invention he believes the ancient engineers used to make
28:19their lighthouse quake-proof.
28:24A mortar of molten lead that they pour between their building blocks.
28:32We do a lot of tests.
28:34We do a lot of tests. Usually most of our tests are on modern building like steel and concrete, reinforced
28:39concrete building.
28:40But today we're doing the lighthouse test.
28:44Adel uses an earthquake simulator to investigate this special mortar.
28:51He wants to find out how it changes the properties of the stone tower.
28:55Oh, that's good.
28:58When you have an earthquake, you're pretty much shaking your building back and forth, so that generates huge forces.
29:05So we're representing these forces by using an actuator here.
29:12It has to be too tight. We don't want any weak link.
29:15The whole idea is that we're simulating earthquake loads until we fail this wall.
29:20We're going to see how much load it's going to take.
29:25Adel's hydraulic pumps rock the granite wall and its mortar with a 10,000 pound force.
29:33That's pretty much like an 8.0 earthquake.
29:39The lead compresses as the wall shakes.
29:43This give in the structure allows the wall and the lighthouse to roll with the punches during a quake.
29:52It's still not broken even with a magnitude 8.0 earthquake.
29:57It's pushing the steel and we can't break it with this molten lead.
30:01Adel inspects the damage.
30:03The wall is intact. There is no even minor cracks.
30:08Everybody will tell you that's a wall that has never experienced an earthquake before.
30:12That's a brand new wall.
30:17Adel believes Alexandria's ingenious lead mortar protects the lighthouse walls against even the most powerful earthquakes.
30:26I have never seen this type of behavior in any types of walls.
30:30That's even stronger than reinforced concrete walls that we have tested before in this lab.
30:38Alexandria's granite and lead lighthouse appears indestructible.
30:43Adel's tests reveal how it can stand for so long, surviving 20 massive earthquakes and more than 1,500 years.
30:53The ancient Egyptians build the lighthouse for the long haul.
30:56They incorporate the smartest Alexandrian engineering into its structure.
31:04Adel believes they even use the same tricks that modern engineers use to build skyscrapers that can ride out monster
31:12quakes.
31:13To build a skyscraper, the ideal way to resist earthquake loads is to have very strong walls at the outside
31:22of the building.
31:23So that's exactly what the Egyptians did.
31:25And that's exactly what we do in modern days as engineers.
31:29Now we realize that the Egyptians have figured this out before we did.
31:36The Alexandrians know that a building with rigid foundations is vulnerable in an earthquake.
31:47So they build their lighthouse so it can move freely on its foundations and ride out the tremors of a
31:54quake without breaking.
32:00So how does the lighthouse finally fall?
32:07Adel uses archaeological data to simulate the exact forces he believes destroy the real lighthouse.
32:15The yellow pixels reveal a structural Achilles heel where the building fails.
32:22We got a lot of movement at the middle segment of the lighthouse.
32:27And as you can see there is a partial collapse of this port and that matches very well with the
32:34historical data we have regarding the failure of the lighthouse of Alexandria.
32:40Adel's virtual model reveals that it's the upper stories that fail.
32:48Where Adel believes there's no lead mortar to hold them together.
32:54They didn't use lead at the top and that's why the collapse of the lighthouse and the failure mainly happened
33:00at the top segments of the lighthouse.
33:02We saw that the base survived in every single earthquake.
33:08Engineering brilliance keeps the lighthouse of Alexandria standing for so long.
33:14Its height and strength make it a wonder of the ancient world.
33:19But doesn't even greater achievement represent its crowning glory?
33:26An ingenious mirror system that turns the beacon of Alexandria into a weapon of war?
33:48The lighthouse of Alexandria is a marvel of ancient engineering.
33:54Over 300 feet tall, standing for more than 1500 years.
34:01One of the seven wonders of the ancient world is its real wonder its ingenious and powerful beacon.
34:15At the base of the lighthouse, an immense doorway.
34:22It opens into a 240 foot shaft that makes it easy to winch up fuel to a chamber at the
34:29top.
34:30In here, a mighty fire burns through the night.
34:35Some scholars believe a system of mirrors focuses the light so much that the lighthouse is visible 35 miles away.
34:48But can it produce, as rumors claim, enough heat to set a ship on fire?
34:58Marty Jopson builds scientific models.
35:04Today at his workshop, he investigates if the lighthouse lives up to its fearsome reputation.
35:12As a death ray, Marty uses modern equipment to replicate the power of the ancient beacon.
35:20I've taken a space blanket.
35:25Suck the air out from behind and you get a perfect parabola which focuses the light into a point.
35:32And the idea is I'm then going to focus that onto this beautiful model boat when the sun comes out.
35:43These are welding glasses because the focal spot is so bright, it's quite dazzling.
35:55Marty moves the target into the death ray's kill zone and angles the mirror to capture the sunlight.
36:04I just need to bring this in a little bit more to about there.
36:08Let's see how that is.
36:11Right, let's try and set it on fire now.
36:15Okay, sun, power on.
36:17And full sun and...
36:21Wow, immediately it's burning!
36:23That!
36:25The mirror focuses the sun's rays to scorch the wooden ship's hull.
36:30Yeah, it's burning, it's burning!
36:33We set fire to it.
36:35Within seconds, the whole ship is ablaze.
36:40All of the energy of the sun that's landing on this mirror is being concentrated to a point about two
36:47centimetres in diameter.
36:49And that is then setting fire to it because the temperature there is in excess of 550 degrees.
36:56That has set fire to that, I think.
36:58Yep, that's set fire to that quite effectively.
37:03Marty's built a miniaturized ship-burning weapon.
37:07Can the ancient Greeks do this on a larger scale?
37:12Their biggest challenge?
37:14To focus the light onto ships across a much greater distance.
37:21Archimedes was an ancient Greek and he was a brilliant mathematician and a brilliant inventor and all sorts of things.
37:26And there was a legend that has it that he built something like this, a burning mirror to set fire
37:33to ships.
37:34And we know that he studied in Alexandria.
37:39How can the Greeks build a death ray with the technology available in the third century BC?
37:50Archimedes is one of the most brilliant engineers of the ancient world.
37:54Famous for designing fireball catapults and ship grabbing claws.
38:02At the Library of Alexandria, he studies the principles of optics and mirrors.
38:11Some scholars believe metal workers at this time have the skill to craft large, high-precision mirrors.
38:20It's technically possible the lighthouse engineers combine Archimedes' knowledge of optics with superb craftsmanship to create a lighthouse death ray.
38:32Now, there are lots of ways you could do this.
38:35The one of the ways that we believe Archimedes did it is that he might have had small hexagonal mirrors,
38:41so sort of an array of little mirrors, each that could be focused separately.
38:46You could have done it with polished shields.
38:48You could have done it with just like a big sheet of copper or brass that you polish and get
38:52it into the right shape.
38:53It's all sorts of different ways this could have been done.
38:57To be sure the lighthouse can function at night as well as in bright daylight, Marty has another test.
39:05He's proved his device is a killer at short range.
39:10But is it also a lifesaver at long distance?
39:15Normally, when sun hits the mirror, it's focused to a focal point, sort of about there, I reckon.
39:23If we put some light here, and it could be, say, a bonfire at the top of the lighthouse of
39:29Alexandria, for example,
39:31then what you'll end up with is a beam that shoots across the valley.
39:35Well, at least that's the theory.
39:36The sun's about to set, so we can give this a try and see how far we can see it.
39:43Marty replicates the lighthouse bonfire with a small LED bulb.
39:48Power on.
39:51So, let's see where I can see it from.
39:58As the sun drops behind the horizon, Marty dashes 300 feet to the end of the field.
40:06Can he make out the bulb's light reflected in the mirror?
40:11That is ridiculously bright.
40:13We're, what, 300 feet, something like that?
40:16And it is one light about, oh, yay big, that's creating all that.
40:21But the question is, how bright will it be if we go right down in the valley?
40:35That is astonishing.
40:37I'm gobsmacked.
40:38It is so bright.
40:41I mean, I reckon we've come down about a mile away onto the main road.
40:46And it's, I mean, you can see sort of on the, on the top of the hill, you can see
40:51the, the car headlights.
40:53And it is 10, 20, 30 times brighter than those.
40:58And this is one LED.
40:59I mean, you can imagine that if they had this at the top of the lighthouse, that would have been
41:06pretty astonishing.
41:10The lighthouse of Alexandria is a marvel of ancient engineering.
41:16A combination of thousands of years of Egyptian know-how into how to build big.
41:23And the technological genius of the ancient Greeks.
41:30Alexandria was an extraordinary place.
41:33It was a meeting place of brilliant minds.
41:37From its granite and lead construction.
41:42To its miraculous mirrors.
41:45The architecture, scale and sheer ambition of the legendary lighthouse of Alexandria.
41:50Combined to create a marvel of engineering brilliance.
41:54And a true wonder of the ancient world.
42:20A great future of the ancient, a beautiful.
42:23A beautiful future ofDAY.
42:27This is the future of this古ain image called the Carrefour.
42:27The Toys.
42:27Oh my gosh.
42:28I know I am a great friend.
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