"[ Narrator] Drawings no one can see." "Plans written in code." "Clues to Leonardo da Vinci's hidden obsession- the quest to ﬂy." "[ Engine Rumbling ]" "It will take hundreds of years to decode the secrets of ﬂight- secrets revealed by big history." "We think of history as a timeline... a series of events stretching a few thousand years into the past." "It's time to think bigger." "Instead of a line, imagine a web of infinite connections... interacting over billions of years... linked together to create everything we've ever known- our universe, our planet... and us." "When we consider our most epic moments though the lens of science... we unleash a revolutionary new idea- the movement of atoms steered the movements of men... civilizations, galaxies." "History as we know it is about to get big." "One of the greatest minds in history... tries to crack an impossible code." "Leonardo da Vinci fills 100 pages of notebooks... with drawings of birds and bats... and designs for strange machines." "His thoughts are consumed with one goal:" "How can a man ﬂy?" "Traditional history tells us that the Wright brothers... are the first to achieve the dream of powered ﬂight... centuries after da Vinci." "But big history reveals how man's quest to ﬂy... is a riddle that' is written at the beginning of time itself." "Big history connects back... more than 13.7 billion years." "We are traveling through the early universe... just' a fraction of a second after the big bang." "Matter comes into existence... along with gravity." "From the beginning of the universe, gravity will rule matter... and act as an invisible barrier to ﬂight." "On some planets, like Jupiter... gravity is so strong, it would crush us." "On other worlds, like the moon... it's so weak that it takes almost no effort to leap several feet up." "[ Astronaut Chattering ]" "[ Narrator] Earths gravity is in the middle." "Strong enough to keep us bound to land... yet weak enough to let some creatures ﬂy." "[ Buzzing ]" "So how do insects and birds defy gravity?" "It turned out that birds were better evolved for ﬂight." " [ Narrator] It's not' just the wings." " [ Screeches ]" "It's the power behind them." "Flapping their wings gives birds the thrust they need to get airborne." "Ana' a birds chest and shoulder muscles... which work the wings... make up as much as 50% of the bird's weight." "In humans, these same muscles account for less than five percent... of our body weight." "So birds have 10 times the ﬂight power we do." "So no matter what da Vinci designs... people can't ﬂy like birds." "Humans need a different strategy." "This is the age of engines." "Machines with 50 times the power of a man." "Two bicycle mechanics, Orville and Wilbur Wright... believe that an engine running on gasoline... can generate enough thrust to lift an aircraft into the sky." "But the engines of their day are made of iron and steel... metals that are strong but heavy." "Everything about the Wrights' plane has to be strong and light." "If the engine's too heavy, the plane won't get off the ground." "To defy gravity, the Wright brothers need a game-changer." "Big history connects the first ﬂight... to the chemistry of a miracle metal." "It's strong and ﬂexible... and three times lighter than steel." "It's a very light metal, but it's also very, very strong." "That's a great combination." "[ Narrator] It's the most common metal on the planet- aluminum." "This unique metal is never found in its pure form." "Aluminum atoms grab on to oxygen and minerals in the Earth's crust... and won't let go." "It's so hard to extract... that in the late 1800s... aluminum is more valuable than gold." "So valuable that France displays a few precious bars... alongside the country's crown jewels." "The metal becomes an international symbol... of wealth and power." "When the Washington Monument was going up in the 1880s... the U.S. put aluminum on the very top of it- a little six-inch pyramid that would kind of announce to the world... just how mighty the United States was." "[ Narrator] But aluminum is 26 million times more common than gold." "And it's about to become a household word." "A young chemist in Ohio, Charles Hall... shoots an electric current through a chemical solution." "The electricity separates the atoms that bind aluminum." "That finally unlocks the potential of a metal... with a unique combination of lightness and strength." "Hall creates the Aluminum Company of America, or Alcoa... to bring the miracle meta!" "to the masses." "That's good news for Hall's fellow Ohioans... the Wright brothers." "They make the crankcase of their airplane engine out of Alcoa aluminum... and it cuts the engine's weight almost in half." "But gravity hasn't been defeated yet." "The rest of their airplane also has to combine strength with lightness." "Big history has a solution... that's been waiting for Orville and Wilbur... since before the time of the dinosaurs." "Big history uses science to see the world in a new way." "It reveals how birds use muscle power to defy gravity... and that man's quest to conquer the sky is impossible... without the power of engines... and strong materials... that are also light... like aluminum." "But gravity is the eternal enemy of ﬂight." "And the Wright brothers still face the problem of weight." "The Wrights have their plane." "The wings provide lift... and the engine gives it power." "But the structure must be light enough to get airborne... yet strong enough to support the weight of the engine... and the pilot." "What material can do all this?" "Once again, the planet supplies what they need." "Big history connects back... to a prehistoric supercontinent." "300 million years ago... most of the land on Earth... clusters into the supercontinent Pangaea." "The vast interior of Pangaea... is hundreds of miles from the cool breezes of the shore." "The land dries out." "Without enough moisture, many trees die... but some adapt." "They develop cones to protect their seeds." "These trees survive- trees like spruce." "After Pangaea breaks apart... spruce trees are carried all over the world." "Their wood has a unique quality." "Heavier, heartier woods like your oaks and all of that" "They're just too heavy." "Lighter woods are too weak." "They're too brittle." "Spruce kind of falls in the middle." "They have just the right amount of high tensile strength." "Makes it ideal for making aircraft out of." "[ Narrator] Big history brings together the strength and lightness of spruce... and aluminum... with the power of the gasoline engine... at the ideal moment... to defy gravity" "[ Engine Rumbling ]" "And lift a man into the air." "Earth gives humanity the Keys to the sky." "One airplane... transforms... into a world of ﬂight." "Now, in a single day... more than 90,000 planes take ﬂight around the world." "[Valle ] If it wasn't for that big history moment... of the Earth drying out, effectively... we wouldn't have that powered ﬂight." "It was the planet drying out and this one tree going..." ""Hey, I can live here now."" "Big history allows us to piece that all together." "[ Narrator] Today, we take ﬂying for granted." "But there was a time on Earth when ﬂight didn't exist at all." "So who were the world's first ﬂiers?" "And when did they first take to the sky?" "Big history links back to a prehistoric forest... more than 325 million years ago... when the first creature on Earth ever to take wing... isn't a bird." "It's a primitive insect." "Possibly, as it falls from a tree... it vibrates nubs on its back... and glides to safety." "Over generations... the nubs evolve into wings." "[Valle ] Flight is the best way to get around this planet." "You can use it to travel." "You can use it to mate." "You can use it to hunt for food, escape predators." "[ Narrator] Flight is a strategy for survival... a strategy that paves the way for humans." "[Screeching ]" "Big history connects forward 260 million years... to a moment of impact." "An asteroid the size of Mount Everest... is on a collision course with Earth." "The dinosaurs are doomed." "[ Groans ]" "[ Narrator] Except for one group that manages to escape- the dinosaurs that evolved into today's birds." "One of the reasons that birds survived... the extinction at the end of the Cretaceous... is probably ﬂight." "If you can ﬂy away, get up above the burning forest... try to find small little areas that weren't burning... maybe an island in a great lake type situation... you can survive." "Flight got 'em out of there." "[ Shrieks ]" "[ Narrator] Their survival is linked to ours." "[ Buzzing ]" "We need birds and ﬂying insects to spread and pollinate... the plants we rely on for food." "One could certainly argue that if there had been no ﬂight... there would be no humans." "[ Narrator] So we depend on ﬂight." "But ﬂight depends on something special about the Earth." "There's a clue in a famous catastrophe- a fiery crash... that reveals how the planet makes ﬂight possible." "Big history connects the story of ﬂight... to the birth of the universe... revealing how gravity emerges within an instant of the big bang... and becomes the enemy of ﬂight." "How nature fights back... combining lightness and strength." "And how humanity cracks the code by harnessing elements... millions of years in the making." "But big history reveals there's another player at work in ﬂight." "[ Man ] Big history is not satisfied... by simply looking at the human history of ﬂight." "Does the planet play any role in enabling ﬂight?" "[ Narrator] Big history looks for answers... in history's most famous ﬂight disaster" "the German zeppelin Hindenburg." "Four diesel engines power an airship filled with seven million cubic feet of gas." "In the final fee!" "Of its 4,600-mile journey from Berlin-.." "The Hindenburg bursts into ﬂames." "But understanding why the Hindenburg falls... is to reveal what first made it take ﬂight." "Big history links the death of the Hindenburg... to the birth of our atmosphere." "A!" "first', ifs a poisonous mix of carbon dioxide and methane." "Then other gases take over... mostly nitrogen... and eventually the gas we will one day breathe." "Oxygen, originally, was put into the atmosphere... by bacteria, as a waste product." "[ Narrator] Even though we can't see gases... they're a form of matter made up of atoms... that have weight." "Some gases are lighter than others." "So any gas lighter than Earth's atmosphere... will ﬂoat." "Six gases are lighter than our atmosphere... including the one that fills the Hindenburg- hydrogen, the most common element in the universe." "But it's also highly ﬂammable." "And because gases in the atmosphere can carry electric charges... its a simple spark of static electricity... that' dooms the Hindenburg." "[ Siren Wailing ]" "But the atmosphere that carries the Hindenburg's destruction... is also what supports it... and everything else that ﬂies." "Just as water provides an environment for swimming..." "Earth is atmosphere, thinner than water. -." "But with many of the same qualities... gives us something to push against... so we can ﬂy." "Let's get a bird and give him a space suit just over his face... and put him in space." "And he's gonna ﬂap like crazy and go nowhere." "Things can't ﬂy in space by ﬂying as we know it." "Why is this?" "Because ﬂying requires you to have wings that are pushing against something." "When you do a pushup, you're using the ground to lift yourself up." "When you're ﬂying, you're using your wings... to push against molecules to lift yourself up." "[ Narrator] And the force holding this invisible ocean in place?" "Gravity... pulling on the atoms of gas to keep them around the planet." "[ Benjamin ] You're trying to strike this delicate balance... between using the atmosphere to support you... and to overcome the, sort of, pull of gravity." "Earth has just the right amount of gravity... just the right density of atmosphere to make ﬂight possible." "[ Narrator] The eternal enemy of ﬂight... is also what makes ﬂight on earth possible." "So we must rely on gravity while we defy it." "Big history reveals that the planet... is the Key to cracking the code of ﬂight." "But the story of ﬂight is just the beginning." "There's a much bigger puzzle hidden in big history." "Each episode unlocks a clue." "Everyday things like mountains... silver... and cell phones... hold the key." "Watch them all, and you'll see this grand mystery revealed- the big history of time, of space... the big history of us."