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(mysterious music)
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Everything in our universe has its size.
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Planets are big,
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insects are small,
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people are somewhere in between.
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Everything has its place in the grand order.
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But does it have to be this way?
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Does size really matter?
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Wouldn't it be better
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if everything were bigger?
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After all, big animals live longer than small ones
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and studies show that tall people are more successful.
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So why are things the size they are
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and what if we could change that?
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Using the latest science,
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we are going to do the ultimate thought experiment.
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We are going to increase the size of everything,
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and that includes us,
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to see whether a bigger world,
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really is a better world.
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We're going to discover just how much size matters,
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how it defines everything.
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You'll never look at yourself or your world
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the same way again.
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(dramatic music)
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(gentle music)
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You might think this looks like an ordinary house
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on an ordinary sunny morning.
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In fact, you are looking at a parallel universe.
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One just like our own
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but with one important difference.
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(alarm beeping)
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In this universe, we can change the size of things
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just to see what happens.
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We're going to follow a normal guy
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going about his normal day
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and see what happens to him
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when we increase the size of stars, planets
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and living things.
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We'll find out if the way things are
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is the only way they can be
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and explore the consequences of a world
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where things are bigger.
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Call it a thought experiment, if you like.
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Something scientists have always used
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to explore the workings of the universe.
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Thought experiments are vitally important for science
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because with thought experiments
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we have a way to quickly explore
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the realm of possibilities
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before we engage in very detailed calculations.
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So whenever we start any question in science,
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we begin with a thought experiment.
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By changing the size of things,
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we're going to explore the laws of nature
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and find out if there are limits
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to how big things can get.
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It's a thought experiment
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that will give us a deeper understanding
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of how things work in the real world.
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And we're going to begin
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by changing the size of planet Earth itself.
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With a mass of six billion trillion tons,
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that's a six followed by 21 zeroes,
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the planet Earth is only the fifth biggest
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of the eight planets of the solar system.
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Let's compare it with number one, mighty Jupiter.
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Jupiter is 11 times the width of Earth
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and has 318 times the mass.
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What would life be like
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on a Jupiter sized Earth
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and would it even be possible?
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We're going to take things slowly
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and start by gradually making Earth bigger
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until it is twice as wide as it was.
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By growing the planet,
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we are going to find out
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how much its size really matters.
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Our infrastructure,
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roads, bridges and buildings,
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are all tailor made to fit the current Earth.
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So it's no surprise
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they won't cope if the planet starts slowly growing
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towards the size of Jupiter.
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But they're more resilient than you might think.
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Bridges at least
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are designed to expand a little.
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So it'll be a few moments
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before everything falls apart.
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Roads can be rebuilt
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but the most important consequence
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of changing the size of a planet
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is far harder to work around
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and that's gravity.
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Gravity is the key force
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that governs the universe and nature
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on the largest scales.
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And at very basic levels,
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every object in the universe
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is attracting every other object
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according to its mass.
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The more mass, the stronger the force of gravity.
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As the planet continues to grow,
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Earth's gravity will get stronger.
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The first casualties
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would be low Earth orbit satellites.
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Even if their orbits
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grow in proportion with the Earth,
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the planet's higher gravity
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would soon pull the closest down
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into the upper atmosphere.
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Then, atmospheric drag would do the rest.
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Falling satellites are just the beginning.
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But what does higher gravity mean for humanity?
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What would be the effect on our bodies,
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our health
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and how much more gravity can we take?
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As you will see,
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higher gravity is a big challenge.
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There are a few people
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who actually know what life on a bigger planet feels like
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because they've experienced
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something just like higher gravity, G-force.
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To do his job,
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royal air force typhoon pilot Mark Long
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has to deal with extreme G-force.
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G-force is like an increase
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in the gravitational effect.
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Your arms feel heavier.
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You find that breathing's a little bit more difficult
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because you're working harder against the force
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that you wouldn't normally be exposed to.
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So it's like gravity but just more intense.
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(dramatic music)
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Today, he's flying a display routine
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which will push him and his plane to their limits.
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(dramatic music)
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As the plane turns,
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Mark is pushed into his seat by G-force.
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Albert Einstein's equivalence principle
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tells us that the effect on his body
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is just like higher gravity.
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So that what he experiences during some maneuvers
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feels exactly the same
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as being on a higher G planet.
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So I've just bottomed down from a looping maneuver here
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and I'm turning the jet into a barrel roll maneuver.
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It's quite slow
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so the G-force is around two and a half at this point.
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And as I get towards the bottom maneuver,
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it starts to increase.
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Back in our parallel universe,
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Earth is now twice as wide as it was.
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That means the planet's circumference
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and the gravity at the surface
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have also doubled.
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So two G actually feels alright.
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You can look around fine,
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you can move your head
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but everything is just a bit more of an effort.
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Moving around under two G conditions would be tiring.
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Life would be very slow,
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you'd be lethargic,
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moving your legs would feel heavy.
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You'd just take longer to do stuff
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and you would feel tired at the end
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of every activity you tried.
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Our infrastructure destroyed,
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humanity brought to its knees,
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a mere doubling of the radius of the planet
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could be the end of days.
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But we're not finished yet.
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As this is a thought experiment,
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let's just say that everyone survives
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and rebuilds to suit two G.
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It's a world in which standing up
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is to be avoided.
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If I was lying down,
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now the heart hasn't got to work so hard
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and life would be a lot easier.
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The distance between your heart and your head
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is the most crucial thing in the vertical sense
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because your heart has to pump the blood against gravity.
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So the best physique
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is actually fairly muscular, quite short.
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It turns out the upright human design
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doesn't deal well with higher gravity.
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Had our planet been bigger,
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we might never have evolved.
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(mysterious music)
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Unfortunately, two G world
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has yet more pain in store.
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Changing the size of Earth
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upsets the cosmic apple cart.
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Our moon sits in perfect equilibrium with the Earth.
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If you make the Earth twice as large in radius
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and eight times more massive,
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it has a dramatic effect on the moon's orbit.
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The moon would be pulled
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into a strange new orbit
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that would pass much, much nearer to the Earth.
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Not close enough to hit
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but you'd soon see the difference.
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But this moon also has a dark side.
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In its normal orbit,
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the moon causes tides in our oceans
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that are seldom more than 10 meters high.
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If we had tides operating
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with this moon coming very, very close to the Earth
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then in fact, the heights of the tides
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would be extremely high.
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So obviously there are some cities around the world,
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many cities in fact
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which would become uninhabitable under those conditions
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because you'd have these great big tidal waves
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sweeping around the planet.
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With the moon now passing so much closer,
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tides could be up to 1,000 meters high.
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But so far, we are nowhere near the size
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of the largest planet in our solar system.
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(dramatic music)
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But just what is the limit
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for the human body?
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Doing 350 miles an hour at this point
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with the jets accelerating all the time,
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so I'm going through 4G, 5G, up to 6G
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as I turn on to a crowd line.
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At 6G I don't think the human body
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would be able to function on a bigger planet.
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It would be incapacitated.
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You would just be spending your whole time
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trying to fight against the G-force.
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You wouldn't be able to do anything.
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In fact, you'd probably spend your entire life laying down.
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But laying down
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won't help with what happens next.
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Because when the Earth reaches half the width of Jupiter,
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something very strange happens.
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The air itself becomes toxic.
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As the increasing gravity of massive Earth
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pulls the atmosphere closer to the surface,
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the oxygen is more tightly packed in.
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There are more and more oxygen molecules
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inside every lungful.
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That may sound like a good thing
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but oxygen is a highly reactive element.
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We are designed to cope with a certain amount.
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Too much of it can cause violent seizures,
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eye and breathing problems,
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loss of consciousness,
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and eventually death.
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So even the air we breathe
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depends on the size of the planet.
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(dramatic music)
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And we're not finished yet.
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I'm preparing my body right now
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for this onslaught of G's.
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So as soon as I enter that turn, I'm at 9G.
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I can barely move my head
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so I'm forcing my body against the edge of the seat
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to look 'round
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with my reference point ready for pitching up for the loop.
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When I pitch up for the loop,
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I know this could be another 9G maneuver.
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So I've pretensed my body.
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And now as I get to the top of the loop
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I'm relaxing into the G-force.
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I've had the typhoon up to 10.4G
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and it was painful
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and I would hate to be on a plant that's 11G.
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In fact, I'd look for a different planet.
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As the planet nears the size of Jupiter,
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insect and other invertebrates
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will cope better with the higher gravity than humans.
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But that won't help with that happens next.
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With gravity now 11 times what it was,
277
00:14:07,000 --> 00:14:09,223
the moon would be pulled from its orbit.
278
00:14:11,380 --> 00:14:13,430
So if you make the Earth 11 times bigger
279
00:14:13,430 --> 00:14:15,290
which is essentially the size of Jupiter,
280
00:14:15,290 --> 00:14:17,606
the moon can no longer go around the Earth anymore.
281
00:14:17,606 --> 00:14:19,007
It will crash into the Earth
282
00:14:19,007 --> 00:14:21,240
and it'll crash into the Earth in about three hours
283
00:14:21,240 --> 00:14:22,526
from the point
284
00:14:22,526 --> 00:14:24,597
where you actually increase the mass of the Earth.
285
00:14:24,597 --> 00:14:25,630
The Earth's gravity
286
00:14:25,630 --> 00:14:28,863
is now just too strong for the moon to stay in orbit.
287
00:14:34,309 --> 00:14:36,540
(moon exploding)
288
00:14:36,540 --> 00:14:38,253
The result would be catastrophic.
289
00:14:50,820 --> 00:14:53,000
Life as we know it could not survive
290
00:14:53,000 --> 00:14:54,943
an Earth the size of Jupiter.
291
00:14:58,450 --> 00:15:01,653
Size connects every part of our universe.
292
00:15:03,100 --> 00:15:05,550
Changing the size of one thing
293
00:15:05,550 --> 00:15:07,413
can affect almost everything.
294
00:15:09,330 --> 00:15:12,540
So it's time to put the planet back
295
00:15:12,540 --> 00:15:13,727
to the size it was.
296
00:15:20,150 --> 00:15:22,680
If we can't change the size of the planet,
297
00:15:22,680 --> 00:15:25,683
how about changing the size of life on the planet?
298
00:15:28,520 --> 00:15:31,693
Living things come in a huge variety of sizes.
299
00:15:33,354 --> 00:15:35,733
But can we make them bigger?
300
00:15:37,300 --> 00:15:40,023
Will giant hearts and lungs still work?
301
00:15:41,170 --> 00:15:43,493
Will giant legs still support us?
302
00:15:44,830 --> 00:15:47,380
The answer is that it depends.
303
00:15:47,380 --> 00:15:48,740
When it comes to living things,
304
00:15:48,740 --> 00:15:51,023
size works in mysterious ways.
305
00:15:52,922 --> 00:15:54,630
Take insects.
306
00:15:55,516 --> 00:15:57,300
As animals go,
307
00:15:57,300 --> 00:15:58,863
we think of them as small.
308
00:16:00,300 --> 00:16:01,787
Even the very biggest insects,
309
00:16:01,787 --> 00:16:04,755
weight no more than 115 grams
310
00:16:04,755 --> 00:16:08,373
and have wingspans no greater than 28 centimeters.
311
00:16:09,300 --> 00:16:11,300
But 300 million years ago
312
00:16:11,300 --> 00:16:15,220
insects were much, much bigger.
313
00:16:15,220 --> 00:16:16,660
Take meganeura,
314
00:16:16,660 --> 00:16:18,300
a dragonfly-like insect
315
00:16:18,300 --> 00:16:20,673
with a wing span of three quarters of a meter.
316
00:16:22,002 --> 00:16:25,120
Is there a reason history can't repeat itself
317
00:16:25,120 --> 00:16:27,250
and giant insects like Meganeura
318
00:16:27,250 --> 00:16:29,600
take to the skies once more?
319
00:16:29,600 --> 00:16:31,404
Well in fact, there is.
320
00:16:31,404 --> 00:16:34,404
Insects don't have lungs like we do.
321
00:16:35,296 --> 00:16:36,129
Insects breathe
322
00:16:36,129 --> 00:16:37,870
through tiny little openings in their body,
323
00:16:37,870 --> 00:16:39,600
so-called spiracles,
324
00:16:39,600 --> 00:16:41,700
which connect to even finer tubes called tracheals
325
00:16:41,700 --> 00:16:43,361
which permeate the entire body.
326
00:16:43,361 --> 00:16:46,030
So this network transports oxygen
327
00:16:46,030 --> 00:16:47,610
to each and every single cell
328
00:16:47,610 --> 00:16:49,233
and removes carbon dioxide.
329
00:16:50,202 --> 00:16:52,200
It's a system that works well
330
00:16:52,200 --> 00:16:53,993
but only for small bodies.
331
00:16:55,220 --> 00:16:57,250
You might think of the way that insects breathe
332
00:16:57,250 --> 00:17:00,380
as letting oxygen sink in through their tissues.
333
00:17:00,380 --> 00:17:01,430
Now that's fine for everything
334
00:17:01,430 --> 00:17:02,980
that's very close to their body surface
335
00:17:02,980 --> 00:17:04,130
but it becomes harder and harder
336
00:17:04,130 --> 00:17:07,425
to reach structures that are deep inside the body.
337
00:17:07,425 --> 00:17:09,374
And if you become larger and larger,
338
00:17:09,374 --> 00:17:12,660
you have more and more volume relative to your surface area
339
00:17:12,660 --> 00:17:14,100
and therefore it becomes harder and harder
340
00:17:14,100 --> 00:17:15,210
to actually reach the structures
341
00:17:15,210 --> 00:17:16,800
that are deep inside your body.
342
00:17:16,800 --> 00:17:18,530
If the way that insects breathe
343
00:17:18,530 --> 00:17:20,050
limits their size today,
344
00:17:20,050 --> 00:17:23,277
why were they so much bigger in the past?
345
00:17:23,277 --> 00:17:24,840
300 million years ago,
346
00:17:24,840 --> 00:17:26,580
the oxygen content in the atmosphere was a lot higher,
347
00:17:26,580 --> 00:17:28,826
around one and a half times as high as now.
348
00:17:28,826 --> 00:17:31,200
So we now have about 21% oxygen concentration
349
00:17:31,200 --> 00:17:34,764
and it used to be 32, 31 percent.
350
00:17:34,764 --> 00:17:36,670
In today's atmosphere,
351
00:17:36,670 --> 00:17:40,413
insects this big just can't get enough oxygen to function.
352
00:17:44,710 --> 00:17:48,030
Insects today have to be small to thrive.
353
00:17:48,030 --> 00:17:50,180
They have already reached their size limit.
354
00:17:55,120 --> 00:17:56,695
But for other living things,
355
00:17:56,695 --> 00:17:58,626
the rules are different.
356
00:17:58,626 --> 00:18:02,223
And some people are already making giant happen.
357
00:18:05,690 --> 00:18:07,400
My twin brother and I,
358
00:18:07,400 --> 00:18:09,610
we live and breathe pumpkins.
359
00:18:09,610 --> 00:18:11,526
We always have done.
360
00:18:11,526 --> 00:18:14,470
These two men have devoted their lives
361
00:18:14,470 --> 00:18:17,013
to making pumpkins into giants.
362
00:18:19,310 --> 00:18:22,030
When he and I were little kids,
363
00:18:22,030 --> 00:18:23,760
we took one of these seeds
364
00:18:23,760 --> 00:18:26,290
and we planted it before we went on holiday.
365
00:18:26,290 --> 00:18:27,750
And since thereabouts
366
00:18:27,750 --> 00:18:28,583
we haven't stopped
367
00:18:28,583 --> 00:18:29,980
and that's 42 years ago.
368
00:18:29,980 --> 00:18:32,263
And it's just out of total passion really.
369
00:18:35,441 --> 00:18:38,640
The seed is, they're like race horses.
370
00:18:38,640 --> 00:18:40,433
We can look year to year
371
00:18:40,433 --> 00:18:42,420
and you'll see that they get a pedigree
372
00:18:42,420 --> 00:18:44,470
and then you know that this seed in particular
373
00:18:44,470 --> 00:18:48,140
will grow lots of pumpkins to 2,000 pounds.
374
00:18:48,140 --> 00:18:49,750
It's a competitive business
375
00:18:49,750 --> 00:18:52,650
and the brothers put plenty of time and money
376
00:18:52,650 --> 00:18:54,420
into their passion.
377
00:18:54,420 --> 00:18:56,880
But however much work the brothers put in,
378
00:18:56,880 --> 00:19:00,313
there's one thing that limits how big a pumpkin can get.
379
00:19:01,420 --> 00:19:03,090
After around 100 days,
380
00:19:03,090 --> 00:19:05,830
pumpkins are genetically programmed to stop growing
381
00:19:05,830 --> 00:19:08,320
as their skins thicken and harden.
382
00:19:08,320 --> 00:19:11,243
So growing the biggest pumpkin is all about speed.
383
00:19:12,660 --> 00:19:14,470
It's physically got to grow that fast.
384
00:19:14,470 --> 00:19:17,310
So next year, we'll be putting the heating up at night
385
00:19:17,310 --> 00:19:18,870
to 22 degrees.
386
00:19:18,870 --> 00:19:20,407
We need to get this thing growing
387
00:19:20,407 --> 00:19:22,650
faster than 57 pounds a day.
388
00:19:22,650 --> 00:19:24,940
So we need to get it going as fast as we can.
389
00:19:24,940 --> 00:19:27,870
And it's just getting everything perfect
390
00:19:27,870 --> 00:19:29,663
and speed, speed, speedy really.
391
00:19:33,810 --> 00:19:35,980
It's a nerve wracking time for us.
392
00:19:35,980 --> 00:19:39,917
That's a year and a massive amount of work.
393
00:19:39,917 --> 00:19:41,060
It'll be the biggest one yet.
394
00:19:41,060 --> 00:19:42,291
I told you.
395
00:19:42,291 --> 00:19:44,120
That's good news.
396
00:19:44,120 --> 00:19:45,123
Bit more.
397
00:19:48,760 --> 00:19:50,170
Done.
398
00:19:50,170 --> 00:19:51,660
Good job.
399
00:19:51,660 --> 00:19:52,910
We need to get the world record
400
00:19:52,910 --> 00:19:54,560
and we're getting close to it
401
00:19:54,560 --> 00:19:56,730
and we've grown some big ones this year
402
00:19:56,730 --> 00:19:57,850
so we'll see how we do.
403
00:19:57,850 --> 00:20:00,130
Hopefully our season's gonna get rewarded
404
00:20:00,130 --> 00:20:01,163
with something good.
405
00:20:02,405 --> 00:20:05,322
(mysterious music)
406
00:20:10,850 --> 00:20:12,810
If it works for pumpkins,
407
00:20:12,810 --> 00:20:15,040
why can't people move up the scale
408
00:20:15,040 --> 00:20:17,060
to challenge the blue whale,
409
00:20:17,060 --> 00:20:18,833
the biggest animal of all time?
410
00:20:21,550 --> 00:20:23,650
Perhaps giants of legend
411
00:20:23,650 --> 00:20:25,775
could be made a reality.
412
00:20:25,775 --> 00:20:28,442
(alarm beeping)
413
00:20:29,310 --> 00:20:30,810
If two men can make a pumpkin
414
00:20:30,810 --> 00:20:33,690
200 times as big as a pumpkin should be,
415
00:20:33,690 --> 00:20:35,030
surely we can make a human
416
00:20:35,030 --> 00:20:37,380
just three times normal size,
417
00:20:37,380 --> 00:20:38,680
five meters tall.
418
00:20:46,074 --> 00:20:47,610
Not a real giant,
419
00:20:47,610 --> 00:20:50,517
but way taller than any human has ever been before.
420
00:20:58,764 --> 00:21:00,521
A human being five meters tall may look possible
421
00:21:00,521 --> 00:21:03,543
but they would be doomed to fail.
422
00:21:04,700 --> 00:21:07,053
To find out why, we need to go to Turkey.
423
00:21:18,158 --> 00:21:21,000
When I go to a hotel or to a friends,
424
00:21:21,000 --> 00:21:23,940
the biggest problem is finding a bed I fit in.
425
00:21:23,940 --> 00:21:25,927
The standard bed is just two meters.
426
00:21:25,927 --> 00:21:28,023
I usually put two beds together.
427
00:21:29,270 --> 00:21:31,258
As well as having oversized feet,
428
00:21:31,258 --> 00:21:34,620
Sultan Kosen has an oversized pituitary gland
429
00:21:34,620 --> 00:21:37,200
that has produced too much human growth hormone
430
00:21:37,200 --> 00:21:39,090
throughout his life.
431
00:21:39,090 --> 00:21:41,600
As a result, he is tall,
432
00:21:41,600 --> 00:21:43,995
2.51 meters tall, to be specific
433
00:21:43,995 --> 00:21:46,913
which makes him the world's tallest man.
434
00:21:48,220 --> 00:21:50,210
Being this tall comes with perks
435
00:21:50,210 --> 00:21:51,483
but also problems.
436
00:21:52,420 --> 00:21:53,963
He keeps breaking his legs.
437
00:22:01,630 --> 00:22:04,360
Sultan has traveled from his hometown to Ankara
438
00:22:04,360 --> 00:22:05,360
to visit his doctor.
439
00:22:16,115 --> 00:22:20,032
(speaking in foreign language)
440
00:22:21,540 --> 00:22:24,210
This is the femoral fracture
441
00:22:24,210 --> 00:22:26,380
that has occurred six years ago.
442
00:22:26,380 --> 00:22:28,260
It was a midshaft fracture
443
00:22:28,260 --> 00:22:30,503
which has replaced all the fragments
444
00:22:30,503 --> 00:22:33,660
and this long rod plaque
445
00:22:33,660 --> 00:22:35,480
has been inserted with nails
446
00:22:35,480 --> 00:22:36,840
to stabilize the fragments.
447
00:22:36,840 --> 00:22:40,540
It's a significant relationship
448
00:22:40,540 --> 00:22:41,750
with the length of the bone
449
00:22:41,750 --> 00:22:44,950
because you know that if you apply a force,
450
00:22:44,950 --> 00:22:46,890
on a very long rod,
451
00:22:46,890 --> 00:22:47,990
you can easily break it.
452
00:22:47,990 --> 00:22:50,143
If it is relatively short,
453
00:22:51,240 --> 00:22:52,940
it's not so easy to break it
454
00:22:52,940 --> 00:22:55,653
because of the physical properties of the bone.
455
00:22:58,306 --> 00:23:01,210
Sultan's other problem is more practical.
456
00:23:01,210 --> 00:23:03,150
Like our five meter human,
457
00:23:03,150 --> 00:23:04,483
he keeps falling over.
458
00:23:06,537 --> 00:23:09,117
He cannot walk as we walk.
459
00:23:09,117 --> 00:23:11,690
That's his basic problem.
460
00:23:11,690 --> 00:23:14,673
That's why he's so prone to easy falls.
461
00:23:27,158 --> 00:23:30,370
(speaking in foreign language)
462
00:23:30,370 --> 00:23:31,800
Size doesn't matter.
463
00:23:31,800 --> 00:23:33,140
What matters is health
464
00:23:33,140 --> 00:23:35,057
and overcoming obstructions.
465
00:23:35,057 --> 00:23:37,036
When obstructions are overcome,
466
00:23:37,036 --> 00:23:39,386
it doesn't matter whether you're short or tall.
467
00:23:44,870 --> 00:23:46,150
Sultan's health issues
468
00:23:46,150 --> 00:23:48,020
reveal one of the main problems
469
00:23:48,020 --> 00:23:50,023
faced by large living things.
470
00:23:51,573 --> 00:23:53,690
Something we will need to understand
471
00:23:53,690 --> 00:23:55,573
as we begin to make bigger humans.
472
00:23:59,246 --> 00:24:02,490
A five meter human would be even more likely
473
00:24:02,490 --> 00:24:05,720
to break their legs than Sultan, but why?
474
00:24:05,720 --> 00:24:08,200
To find out, let's make this statue bigger
475
00:24:08,200 --> 00:24:09,333
and see what happens.
476
00:24:17,290 --> 00:24:19,540
You might think you just get a larger statue
477
00:24:20,600 --> 00:24:21,550
but you'd be wrong.
478
00:24:23,320 --> 00:24:24,920
There's something else going on.
479
00:24:29,520 --> 00:24:31,873
Let's try again and find out what.
480
00:24:34,260 --> 00:24:36,440
By the time it's double the size,
481
00:24:36,440 --> 00:24:39,491
the arms weigh eight times what they did
482
00:24:39,491 --> 00:24:41,993
but are only four times as strong.
483
00:24:46,914 --> 00:24:48,990
Why is that?
484
00:24:48,990 --> 00:24:52,294
The statue's weight depends on three dimensions.
485
00:24:52,294 --> 00:24:54,310
So if you double the height,
486
00:24:54,310 --> 00:24:57,000
the weight goes up eight times.
487
00:24:57,000 --> 00:24:59,897
Strength depends on cross sectional area
488
00:24:59,897 --> 00:25:02,520
which is just two dimensional.
489
00:25:02,520 --> 00:25:04,833
So it doesn't increase as fast as weight.
490
00:25:06,300 --> 00:25:07,640
The result?
491
00:25:07,640 --> 00:25:09,544
Arms that fall off.
492
00:25:09,544 --> 00:25:12,960
So if you want to double the size of a statue,
493
00:25:12,960 --> 00:25:15,193
you'll have to reengineer it to be big.
494
00:25:16,880 --> 00:25:18,360
Just ask Venus.
495
00:25:18,360 --> 00:25:19,510
She knows all about it.
496
00:25:22,734 --> 00:25:25,944
So if we're going to make bigger people
497
00:25:25,944 --> 00:25:27,700
we'd better do the same
498
00:25:27,700 --> 00:25:29,633
and reengineer the human body.
499
00:25:30,860 --> 00:25:31,693
But how?
500
00:25:33,502 --> 00:25:34,613
There are plenty of other living things
501
00:25:34,613 --> 00:25:35,860
that have managed to make it
502
00:25:35,860 --> 00:25:37,433
to the bigger end of the scale.
503
00:25:39,890 --> 00:25:42,060
What can we learn from them
504
00:25:42,060 --> 00:25:43,963
about building a giant human?
505
00:25:45,450 --> 00:25:47,390
The tallest living things on the planet
506
00:25:47,390 --> 00:25:48,760
are coast redwoods
507
00:25:48,760 --> 00:25:50,333
to be found in California.
508
00:25:51,990 --> 00:25:55,270
I love these trees because of their massive size,
509
00:25:55,270 --> 00:25:56,480
their old age
510
00:25:56,480 --> 00:26:00,333
and because of the way they build the forest that they do.
511
00:26:01,520 --> 00:26:02,810
Professor Todd Dawson
512
00:26:02,810 --> 00:26:04,550
and his team of scientists
513
00:26:04,550 --> 00:26:06,450
have studied every inch of these trees
514
00:26:11,530 --> 00:26:12,843
right to the very top.
515
00:26:16,250 --> 00:26:19,503
If anyone knows why they're so tall, it's him.
516
00:26:23,760 --> 00:26:27,860
So redwoods are a remarkably long lived tree
517
00:26:27,860 --> 00:26:31,280
and the coast redwood can live more than 2,500 years.
518
00:26:31,280 --> 00:26:33,860
Because they're plants, they're constantly growing.
519
00:26:33,860 --> 00:26:35,430
And because they're very old,
520
00:26:35,430 --> 00:26:38,520
as long as they keep growing and they have that old age,
521
00:26:38,520 --> 00:26:39,353
they're just gonna keep
522
00:26:39,353 --> 00:26:41,163
getting bigger and bigger and bigger.
523
00:26:49,133 --> 00:26:52,990
So a tree like the one we're standing next to here,
524
00:26:52,990 --> 00:26:56,420
it probably weighs thousands and thousands
525
00:26:56,420 --> 00:26:58,853
and thousands of pounds, many tons.
526
00:27:00,126 --> 00:27:02,790
One of the things that we notice about these trees
527
00:27:02,790 --> 00:27:04,120
as they grow
528
00:27:04,120 --> 00:27:07,320
is they begin to add more at the base.
529
00:27:07,320 --> 00:27:09,313
So you go from a very small tree
530
00:27:09,313 --> 00:27:11,430
that just goes right into the ground
531
00:27:11,430 --> 00:27:12,790
like a carrot in the Earth
532
00:27:12,790 --> 00:27:14,163
and as they grow larger,
533
00:27:14,163 --> 00:27:16,550
they get heavier and heavier and heavier,
534
00:27:16,550 --> 00:27:17,620
they begin to buttress,
535
00:27:17,620 --> 00:27:20,020
they begin to add mass at the base
536
00:27:20,020 --> 00:27:22,610
'cause they have to have a way to support themselves.
537
00:27:22,610 --> 00:27:25,438
Eight meters, five centimeters,
538
00:27:25,438 --> 00:27:27,003
nice sized tree.
539
00:27:28,750 --> 00:27:30,920
They sort of built some sort of a structure
540
00:27:30,920 --> 00:27:33,363
like an elephant's foot if you will at the base.
541
00:27:34,620 --> 00:27:37,410
Remarkable set of compensation mechanisms.
542
00:27:39,040 --> 00:27:40,963
So is this the limit
543
00:27:40,963 --> 00:27:43,570
or could we imagine a parallel universe
544
00:27:43,570 --> 00:27:45,797
where the biggest of living things
545
00:27:45,797 --> 00:27:47,387
may be even bigger?
546
00:27:49,340 --> 00:27:50,590
The redwood's strategy
547
00:27:50,590 --> 00:27:52,070
of shape shifting,
548
00:27:52,070 --> 00:27:54,730
getting more triangular as they grow taller,
549
00:27:54,730 --> 00:27:55,940
means that their trunks
550
00:27:55,940 --> 00:27:58,400
can support the weight of taller trees.
551
00:27:58,400 --> 00:27:59,950
But they'd hit another problem.
552
00:28:06,188 --> 00:28:07,380
So one of the factors
553
00:28:07,380 --> 00:28:09,010
that limits how tall trees get
554
00:28:09,010 --> 00:28:10,630
is their ability to get water
555
00:28:10,630 --> 00:28:13,100
to the top of the tree itself.
556
00:28:13,100 --> 00:28:16,490
And while a lot of trees may stop their growth,
557
00:28:16,490 --> 00:28:19,140
redwoods have a special way of dealing
558
00:28:19,140 --> 00:28:22,380
with that water limitation as they get taller.
559
00:28:22,380 --> 00:28:25,503
For example, we've got leaves
560
00:28:25,503 --> 00:28:27,635
that come from the lower part of the ground,
561
00:28:27,635 --> 00:28:28,883
and ah,
562
00:28:31,179 --> 00:28:33,290
these much smaller leaves,
563
00:28:33,290 --> 00:28:35,287
they come from the very top of the tree.
564
00:28:35,287 --> 00:28:37,580
And as the leaf area goes down,
565
00:28:37,580 --> 00:28:41,000
the amount of water used goes down as well.
566
00:28:41,000 --> 00:28:43,200
So they become more thrifty in their water use
567
00:28:43,200 --> 00:28:44,070
at the top of the tree
568
00:28:44,070 --> 00:28:46,170
than they do at the bottom of the tree.
569
00:28:46,170 --> 00:28:49,070
Moving water upwards several hundred feet
570
00:28:49,070 --> 00:28:49,993
needs pressure.
571
00:28:50,910 --> 00:28:52,860
Fluid migrating into the roots
572
00:28:52,860 --> 00:28:54,070
pushes water up
573
00:28:54,070 --> 00:28:55,750
while at the leaves,
574
00:28:55,750 --> 00:28:58,240
sunlight causes water to evaporate
575
00:28:58,240 --> 00:28:59,690
leading to low pressure
576
00:28:59,690 --> 00:29:01,603
which pulls water upwards.
577
00:29:02,500 --> 00:29:04,570
The redwoods smaller leaves at the top
578
00:29:04,570 --> 00:29:06,680
mean only a small amount of water
579
00:29:06,680 --> 00:29:07,780
has to go all the way.
580
00:29:09,620 --> 00:29:11,830
But grow a redwood too tall
581
00:29:11,830 --> 00:29:14,400
and not even those special adaptations
582
00:29:14,400 --> 00:29:16,723
can solve the water supply problem.
583
00:29:17,957 --> 00:29:20,320
The leaves would dry out and die
584
00:29:21,730 --> 00:29:23,623
and the tree would go no further.
585
00:29:30,810 --> 00:29:33,580
Despite their problems getting water to the top,
586
00:29:33,580 --> 00:29:36,530
trees still show us just how big you can get
587
00:29:36,530 --> 00:29:38,423
if you change your shape as you grow.
588
00:29:39,783 --> 00:29:41,360
That means that bigger creatures
589
00:29:41,360 --> 00:29:44,840
can't just be scaled up version of smaller creatures.
590
00:29:44,840 --> 00:29:46,680
They need profound adaptations
591
00:29:46,680 --> 00:29:48,883
to overcome the challenges of size.
592
00:29:53,807 --> 00:29:56,080
Take a dog for example.
593
00:29:56,080 --> 00:29:58,320
This dog's skeleton makes up eight percent
594
00:29:58,320 --> 00:29:59,583
of its total body weight.
595
00:30:01,529 --> 00:30:03,670
But if we want to make it bigger
596
00:30:03,670 --> 00:30:05,220
we'll have to beef it up a bit.
597
00:30:10,690 --> 00:30:12,420
At three times the height,
598
00:30:12,420 --> 00:30:14,080
thicker bones mean a skeleton
599
00:30:14,080 --> 00:30:16,453
that weights 10% of its body weight.
600
00:30:27,220 --> 00:30:29,350
But if we want to make it bigger still,
601
00:30:29,350 --> 00:30:31,683
we've got to overcome yet another problem.
602
00:30:36,460 --> 00:30:39,960
Big animals have less surface area per kilogram of weight
603
00:30:39,960 --> 00:30:41,740
than small ones.
604
00:30:41,740 --> 00:30:45,053
So they have proportionally less skin to lose heat from.
605
00:30:46,020 --> 00:30:47,713
This means they can overheat.
606
00:30:48,870 --> 00:30:50,820
Elephants evolved to be large
607
00:30:50,820 --> 00:30:53,110
so that they could dominate their environment,
608
00:30:53,110 --> 00:30:54,620
be safe from predators
609
00:30:54,620 --> 00:30:56,193
and reach food more easily.
610
00:30:57,120 --> 00:30:58,220
But they also needed a way
611
00:30:58,220 --> 00:31:00,593
to avoid overheating in a hot environment.
612
00:31:03,039 --> 00:31:05,410
Elephants don't just have large ears
613
00:31:05,410 --> 00:31:06,780
because they look good.
614
00:31:06,780 --> 00:31:08,863
They also help them to regulate heat.
615
00:31:13,800 --> 00:31:14,900
Billy, our eight year old,
616
00:31:14,900 --> 00:31:17,150
is being very energetic right now
617
00:31:17,150 --> 00:31:19,880
but we're still seeing because of the colder temperatures
618
00:31:19,880 --> 00:31:24,760
his ears are much colder than the rest of his body.
619
00:31:24,760 --> 00:31:26,730
So it really shows how efficient they are
620
00:31:26,730 --> 00:31:29,040
at controlling their body temperature
621
00:31:29,040 --> 00:31:30,063
by using their ears.
622
00:31:31,511 --> 00:31:33,960
In the summer times, we would see the opposite.
623
00:31:33,960 --> 00:31:35,600
Their ears would be much warmer,
624
00:31:35,600 --> 00:31:37,950
the veins would be full of blood
625
00:31:37,950 --> 00:31:39,910
using it as an air conditioner
626
00:31:39,910 --> 00:31:42,903
helping cool down the rest of the body temperature.
627
00:31:48,640 --> 00:31:50,970
Maybe our giant dog could learn a lesson
628
00:31:50,970 --> 00:31:52,363
from his elephant cousins.
629
00:31:53,200 --> 00:31:54,460
Grow a pair of bigger ears
630
00:31:54,460 --> 00:31:55,930
to increase surface area
631
00:31:55,930 --> 00:31:57,110
and lose the fur,
632
00:31:57,110 --> 00:31:58,493
since hair traps heat.
633
00:31:59,710 --> 00:32:01,800
With stronger bones and a way to keep cool,
634
00:32:01,800 --> 00:32:04,203
we can safely make an even bigger dog now.
635
00:32:06,000 --> 00:32:07,283
But how big can we go?
636
00:32:09,810 --> 00:32:13,133
How about as large as a medium size dinosaur?
637
00:32:14,100 --> 00:32:15,490
Which is just big enough
638
00:32:15,490 --> 00:32:16,890
to run into another problem.
639
00:32:30,660 --> 00:32:32,073
It's just too slow.
640
00:32:42,347 --> 00:32:45,230
Herve Bocherens is a paleontologist
641
00:32:45,230 --> 00:32:48,493
who knows exactly why big animals are so slow.
642
00:32:50,582 --> 00:32:53,309
Large animals have an issue with distance
643
00:32:53,309 --> 00:32:56,307
the signal have to travel along the nerves.
644
00:32:57,920 --> 00:33:02,400
Of course, if you are already about 20 meters long,
645
00:33:02,400 --> 00:33:04,200
the signal has to be both ways
646
00:33:04,200 --> 00:33:07,280
and therefore it's already significant fraction of a second
647
00:33:07,280 --> 00:33:10,690
that takes time for the signal to travel.
648
00:33:10,690 --> 00:33:13,490
And therefore the reaction time of big animals
649
00:33:13,490 --> 00:33:17,230
will be slower than the reaction time of smaller animals
650
00:33:17,230 --> 00:33:20,433
and this will make a difference in their life.
651
00:33:22,440 --> 00:33:24,040
So today for instance,
652
00:33:24,040 --> 00:33:26,550
the largest land animals are elephants
653
00:33:26,550 --> 00:33:27,920
and it has been observed
654
00:33:27,920 --> 00:33:29,971
that elephants have to be quite careful
655
00:33:29,971 --> 00:33:31,780
when they walk
656
00:33:31,780 --> 00:33:35,460
because the signal has to travel quite a long distance.
657
00:33:35,460 --> 00:33:38,166
And when they hit something with their foot, for instance,
658
00:33:38,166 --> 00:33:41,840
it takes a couple of milliseconds
659
00:33:41,840 --> 00:33:42,970
to reach the brain.
660
00:33:42,970 --> 00:33:46,390
And therefore, they hae to wait until the signal comes back
661
00:33:46,390 --> 00:33:48,890
to know if they have hit something with their foot
662
00:33:49,795 --> 00:33:50,628
before they make the next step.
663
00:33:54,170 --> 00:33:56,810
Being slow is not good news for a dog
664
00:33:56,810 --> 00:33:58,720
which needs to catch prey.
665
00:33:58,720 --> 00:34:00,820
A giant dog might starve to death
666
00:34:02,141 --> 00:34:04,233
unless it has someone to feed it.
667
00:34:10,010 --> 00:34:11,440
We've managed a dog,
668
00:34:11,440 --> 00:34:14,090
so it should be straight forward to scale up a human.
669
00:34:16,520 --> 00:34:17,600
First thing to remember
670
00:34:17,600 --> 00:34:20,480
is that a human just five times normal height
671
00:34:20,480 --> 00:34:24,370
would weigh 125 times normal weight.
672
00:34:24,370 --> 00:34:26,343
So he would need much thicker bones.
673
00:34:29,690 --> 00:34:32,070
Then of course he'll need big ears like an elephant
674
00:34:32,070 --> 00:34:33,470
to get rid of all that heat.
675
00:34:36,570 --> 00:34:38,800
But before our giant gets any bigger,
676
00:34:38,800 --> 00:34:41,963
we have to face one challenge that most big animals don't.
677
00:34:43,080 --> 00:34:44,783
Humans walk on two legs.
678
00:34:51,037 --> 00:34:54,470
Herve Bocherens is studying another primate
679
00:34:54,470 --> 00:34:57,420
that tried to get giant in the past.
680
00:34:57,420 --> 00:34:59,913
It's a story that begins in an unusual place.
681
00:35:01,220 --> 00:35:04,434
It started in a Chinese pharmacy in Hong Kong
682
00:35:04,434 --> 00:35:06,320
where a paleontologist
683
00:35:06,320 --> 00:35:09,183
was looking at what is called dragon teeth.
684
00:35:11,620 --> 00:35:13,480
And among these fossil material,
685
00:35:13,480 --> 00:35:15,130
there were some fossil human teeth
686
00:35:15,130 --> 00:35:17,300
but also teeth that were much bigger,
687
00:35:17,300 --> 00:35:18,950
looked like humans.
688
00:35:18,950 --> 00:35:21,150
And these were the first discoveries
689
00:35:21,150 --> 00:35:23,190
of Gigantopithecus.
690
00:35:23,190 --> 00:35:24,970
They weren't dragon's teeth.
691
00:35:24,970 --> 00:35:28,580
They were teeth from the biggest ape to ever live,
692
00:35:28,580 --> 00:35:30,530
Gigantopithecus.
693
00:35:30,530 --> 00:35:33,140
Estimating the size of an animal
694
00:35:33,140 --> 00:35:35,410
based on just teeth and lower jaw
695
00:35:35,410 --> 00:35:37,440
is a difficult thing
696
00:35:37,440 --> 00:35:41,060
but we can say that at least it was twice as heavy
697
00:35:41,060 --> 00:35:42,380
as a gorilla.
698
00:35:42,380 --> 00:35:44,920
So the weight could be up to 500 kilogram
699
00:35:44,920 --> 00:35:47,193
which is a maximum estimate.
700
00:35:48,735 --> 00:35:51,130
That makes it the largest primate
701
00:35:51,130 --> 00:35:53,280
that has ever existed.
702
00:35:53,280 --> 00:35:55,563
But estimating its height is even harder.
703
00:36:00,590 --> 00:36:01,600
Most probably,
704
00:36:01,600 --> 00:36:03,370
it was not standing so much
705
00:36:03,370 --> 00:36:05,230
because with such a heavy weight,
706
00:36:05,230 --> 00:36:07,243
it was probably essentially quadrupedal.
707
00:36:08,416 --> 00:36:12,050
And therefore, it's more a comparison with a gorilla
708
00:36:12,050 --> 00:36:15,140
who is mostly walking on four legs
709
00:36:15,140 --> 00:36:17,023
rather than walking erect.
710
00:36:19,421 --> 00:36:21,900
Gigantopithecus was just too big
711
00:36:21,900 --> 00:36:23,543
to stand tall like a human.
712
00:36:24,943 --> 00:36:27,540
We have many examples of in the past
713
00:36:27,540 --> 00:36:29,610
of animals that started bipedal
714
00:36:29,610 --> 00:36:31,980
and had to go back to their four legs.
715
00:36:31,980 --> 00:36:33,780
And when they grew bigger,
716
00:36:33,780 --> 00:36:35,720
it means that they had to carry their weight
717
00:36:35,720 --> 00:36:36,553
on four legs
718
00:36:36,553 --> 00:36:38,083
and not anymore on two legs.
719
00:36:41,200 --> 00:36:44,900
So as we continue to grow our giant human,
720
00:36:44,900 --> 00:36:48,377
should he walk on all fours like a Gigantopithecus?
721
00:36:57,530 --> 00:36:58,363
Perhaps not.
722
00:37:04,490 --> 00:37:07,030
If it's going to be a giant human,
723
00:37:07,030 --> 00:37:08,940
it has to be bipedal
724
00:37:08,940 --> 00:37:13,560
because bipedalism is the thing, the one major thing,
725
00:37:13,560 --> 00:37:18,500
that sets our genus or our group, the hominids,
726
00:37:18,500 --> 00:37:21,050
off from al of the other primates.
727
00:37:21,050 --> 00:37:22,993
We are habitually bipedal.
728
00:37:24,290 --> 00:37:26,890
Being bipedal has upsides.
729
00:37:26,890 --> 00:37:28,130
Your head is raised
730
00:37:28,130 --> 00:37:30,270
so you can see danger further away.
731
00:37:32,225 --> 00:37:34,383
And you can reach higher to get food.
732
00:37:35,370 --> 00:37:36,350
But for humans,
733
00:37:36,350 --> 00:37:38,980
perhaps the biggest evolutionary advantage
734
00:37:38,980 --> 00:37:41,773
is that it keeps your hands free for other things.
735
00:37:44,992 --> 00:37:45,825
But the bottom line
736
00:37:45,825 --> 00:37:47,610
is if it's not on two legs
737
00:37:47,610 --> 00:37:48,983
it's just not a human.
738
00:37:50,350 --> 00:37:53,430
So if we're going to make a giant bipedal human,
739
00:37:53,430 --> 00:37:55,670
that means we hae to support all that weight
740
00:37:55,670 --> 00:37:56,903
on just two legs.
741
00:37:58,823 --> 00:38:00,290
If you're a giant
742
00:38:00,290 --> 00:38:01,830
and you're really, really tall,
743
00:38:01,830 --> 00:38:05,170
well you've got to get that blood pumped away from the heart
744
00:38:05,170 --> 00:38:07,850
and up to the brain, very important.
745
00:38:07,850 --> 00:38:09,430
So you need a big pump,
746
00:38:09,430 --> 00:38:10,620
a big heart,
747
00:38:10,620 --> 00:38:12,070
and that means a big chest
748
00:38:12,070 --> 00:38:13,490
to put the heart in
749
00:38:13,490 --> 00:38:15,370
and it's gotta go uphill.
750
00:38:15,370 --> 00:38:20,370
And so I might put the heart higher up within the chest.
751
00:38:20,600 --> 00:38:21,780
The heart is just a simple
752
00:38:21,780 --> 00:38:24,630
pump that has to get blood around the body.
753
00:38:24,630 --> 00:38:26,833
And pumping uphill is harder work.
754
00:38:27,935 --> 00:38:31,040
So a giant human needs as short a distance
755
00:38:31,040 --> 00:38:33,163
between heart and brain as possible.
756
00:38:35,140 --> 00:38:37,830
The chances are, however large his heart,
757
00:38:37,830 --> 00:38:40,120
our giant human would be lonely
758
00:38:40,120 --> 00:38:42,600
and not just because to he way he looks.
759
00:38:42,600 --> 00:38:44,530
Another consequence of being large
760
00:38:44,530 --> 00:38:46,330
is that the population will be small
761
00:38:46,330 --> 00:38:48,905
because each one need a lot of food.
762
00:38:48,905 --> 00:38:52,313
And so giants would probably not be very numerous.
763
00:38:53,590 --> 00:38:55,192
Even with a four-legged friend,
764
00:38:55,192 --> 00:38:58,093
life as a giant would be no fairytale.
765
00:38:59,689 --> 00:39:02,770
It would have to be a very strange creature indeed
766
00:39:02,770 --> 00:39:04,380
to overcome all the problems
767
00:39:04,380 --> 00:39:07,033
that being big creates for a human being.
768
00:39:08,210 --> 00:39:12,050
That's because size is intrinsic to everything.
769
00:39:12,050 --> 00:39:14,630
Your size determines what shape you are,
770
00:39:14,630 --> 00:39:16,373
how you live, what you eat.
771
00:39:17,900 --> 00:39:19,350
Change it too much
772
00:39:19,350 --> 00:39:21,793
and you simply get a different species.
773
00:39:22,810 --> 00:39:26,500
So let's put things back to how they were.
774
00:39:32,393 --> 00:39:35,060
(alarm beeping)
775
00:39:37,360 --> 00:39:40,693
We've changed the size of the Earth and everything on it
776
00:39:40,693 --> 00:39:43,120
and it really didn't work
777
00:39:43,120 --> 00:39:46,023
but there's one last thought experiment we can try.
778
00:39:47,344 --> 00:39:50,180
Because if we're going to change the size of things,
779
00:39:50,180 --> 00:39:52,280
we can't miss out something massive
780
00:39:52,280 --> 00:39:54,793
that lies at the very heart of our solar system,
781
00:39:58,490 --> 00:40:01,203
the sun, our nearest star.
782
00:40:03,280 --> 00:40:05,290
But when it comes to stars,
783
00:40:05,290 --> 00:40:06,593
does size matter?
784
00:40:08,598 --> 00:40:13,290
Size is crucial to the work of astrophysicist Volker Bromm
785
00:40:13,290 --> 00:40:14,940
because the size of a star
786
00:40:14,940 --> 00:40:17,180
determines how it behaves.
787
00:40:17,180 --> 00:40:18,200
When you think about stars,
788
00:40:18,200 --> 00:40:21,000
then size is absolutely essential
789
00:40:21,000 --> 00:40:24,020
because you could say that the size of a star,
790
00:40:24,020 --> 00:40:27,347
or more precisely the mass of a star is destiny.
791
00:40:27,347 --> 00:40:30,650
If a star's size is its destiny,
792
00:40:30,650 --> 00:40:32,850
just how big is ours?
793
00:40:32,850 --> 00:40:36,570
Well, it's 109 times wider than planet Earth
794
00:40:36,570 --> 00:40:39,653
and 330,000 times as massive.
795
00:40:40,540 --> 00:40:43,300
It accounts for 99.86 percent
796
00:40:43,300 --> 00:40:45,703
of all mass in the solar system.
797
00:40:47,640 --> 00:40:48,970
As it turns out,
798
00:40:48,970 --> 00:40:51,383
just the right size for life on Earth.
799
00:40:52,740 --> 00:40:55,980
The sun is, for us, the essential star.
800
00:40:55,980 --> 00:40:59,110
The sun really provides us with a perfect cosmic environment
801
00:40:59,110 --> 00:41:01,520
to enable life on Earth.
802
00:41:01,520 --> 00:41:04,200
How do we know the sun is so perfect?
803
00:41:04,200 --> 00:41:05,084
One way to find out
804
00:41:05,084 --> 00:41:07,890
is to visit our parallel universe,
805
00:41:07,890 --> 00:41:09,200
make the sun bigger
806
00:41:09,200 --> 00:41:11,023
and see if the world survives.
807
00:41:13,060 --> 00:41:15,193
Let's start by imagining our sun
808
00:41:15,193 --> 00:41:18,093
but with exactly double the amount of gas.
809
00:41:23,080 --> 00:41:25,267
You might imagine it would be twice as bright
810
00:41:25,267 --> 00:41:26,503
but you'd be wrong.
811
00:41:32,140 --> 00:41:34,100
How a star reacts to increasing the mass
812
00:41:34,100 --> 00:41:36,320
is highly nonintuitive.
813
00:41:36,320 --> 00:41:37,920
So you double the mass
814
00:41:37,920 --> 00:41:41,033
and you increase the energy output tenfold.
815
00:41:43,050 --> 00:41:43,970
On Earth,
816
00:41:43,970 --> 00:41:45,713
the effects would be staggering.
817
00:41:47,290 --> 00:41:49,250
The equilibrium temperature on Earth
818
00:41:49,250 --> 00:41:51,490
would go up by a significant factor.
819
00:41:51,490 --> 00:41:52,500
So we would have a much hotter Earth
820
00:41:52,500 --> 00:41:54,130
which would then suddenly
821
00:41:54,130 --> 00:41:56,453
become completely inhospitable.
822
00:41:57,660 --> 00:42:00,483
First, the ice caps would melt.
823
00:42:06,263 --> 00:42:08,903
Then the oceans and rivers would dry up.
824
00:42:09,870 --> 00:42:12,330
The surface of the Earth would eventually stabilize
825
00:42:12,330 --> 00:42:14,233
at over 200 degrees centigrade.
826
00:42:20,010 --> 00:42:21,520
But all is not lost.
827
00:42:21,520 --> 00:42:24,463
There is one way we could get things back to normal.
828
00:42:25,770 --> 00:42:28,870
A key question in modern astronomy
829
00:42:28,870 --> 00:42:32,470
is that we think about the region around any star
830
00:42:32,470 --> 00:42:36,069
where life, in principle, could be sustained.
831
00:42:36,069 --> 00:42:38,820
For life as we know it to exist,
832
00:42:38,820 --> 00:42:41,090
the temperature of a planet needs to be right
833
00:42:41,090 --> 00:42:43,800
for water to exist as a liquid.
834
00:42:43,800 --> 00:42:46,870
The area around any star where this could happen
835
00:42:46,870 --> 00:42:48,473
is called the goldilocks zone.
836
00:42:49,480 --> 00:42:51,990
You basically have a very, very special region
837
00:42:51,990 --> 00:42:52,920
around any star
838
00:42:52,920 --> 00:42:55,555
and this goldilocks zone of not too hot, not too cold,
839
00:42:55,555 --> 00:42:57,650
what we call the habitable zone
840
00:42:57,650 --> 00:43:00,680
is a very precious, precarious zone
841
00:43:00,680 --> 00:43:02,900
because if you play with the conditions in the central star
842
00:43:02,900 --> 00:43:04,540
everything changes.
843
00:43:04,540 --> 00:43:07,450
As a double mass sun burns so much hotter,
844
00:43:07,450 --> 00:43:10,423
this means the goldilocks zone is now further away,
845
00:43:11,260 --> 00:43:13,003
three times further away.
846
00:43:14,062 --> 00:43:16,580
So we just need to move planet Earth
847
00:43:17,500 --> 00:43:19,360
to its new resting place,
848
00:43:19,360 --> 00:43:20,680
well past Mars,
849
00:43:20,680 --> 00:43:24,823
450 million kilometers from the bigger sun.
850
00:43:26,010 --> 00:43:28,760
Here, life would not be in immediate danger.
851
00:43:28,760 --> 00:43:30,370
But it's far from ideal.
852
00:43:30,370 --> 00:43:34,840
The new longer orbit means a year is much longer.
853
00:43:34,840 --> 00:43:36,400
And so are the seasons.
854
00:43:36,400 --> 00:43:39,200
In fact, winter would last 16 months
855
00:43:39,200 --> 00:43:41,843
which would make growing crops very difficult.
856
00:43:43,000 --> 00:43:45,853
So could Earth survive around an even bigger sun?
857
00:43:46,989 --> 00:43:48,770
Before we can answer that,
858
00:43:48,770 --> 00:43:51,836
we need to know just how big stars get.
859
00:43:51,836 --> 00:43:54,586
(dramatic music)
860
00:43:56,090 --> 00:43:59,410
Since mankind first invented the telescope,
861
00:43:59,410 --> 00:44:02,613
we have wondered just how big the stars really are.
862
00:44:04,680 --> 00:44:05,780
This is what we found.
863
00:44:08,000 --> 00:44:10,807
We think of our sun as pretty big
864
00:44:10,807 --> 00:44:13,370
but in the universe's hall of fame,
865
00:44:13,370 --> 00:44:14,767
it's just a nobody.
866
00:44:28,470 --> 00:44:30,480
The biggest star by radius
867
00:44:30,480 --> 00:44:32,250
that mankind has every observed
868
00:44:32,250 --> 00:44:35,250
is known as UY Scuti.
869
00:44:35,250 --> 00:44:40,029
It's more than 1,700 times the width of our sun.
870
00:44:40,029 --> 00:44:42,050
But there are stars even bigger
871
00:44:42,050 --> 00:44:44,170
if we look far enough away.
872
00:44:44,170 --> 00:44:46,833
Not just in distance but in time.
873
00:44:47,890 --> 00:44:48,760
In astronomy,
874
00:44:48,760 --> 00:44:51,680
we have a great privilege.
875
00:44:51,680 --> 00:44:54,230
We can do something that historians and archeologists
876
00:44:54,230 --> 00:44:55,300
only dream of.
877
00:44:55,300 --> 00:44:59,100
We can directly take images of the distant past.
878
00:44:59,100 --> 00:45:01,210
And we do this by looking at objects
879
00:45:01,210 --> 00:45:03,063
that are far away in the universe.
880
00:45:04,337 --> 00:45:05,630
Objects that are far away,
881
00:45:05,630 --> 00:45:07,040
they have sent out the light
882
00:45:07,040 --> 00:45:10,110
that we receive billions of years later
883
00:45:10,110 --> 00:45:12,087
and light travels with a limit of speed,
884
00:45:12,087 --> 00:45:13,110
the speed of light.
885
00:45:13,110 --> 00:45:15,950
And therefore looking far out into space
886
00:45:15,950 --> 00:45:18,683
means also looking far back into time.
887
00:45:20,967 --> 00:45:22,810
When they looked far enough away
888
00:45:22,810 --> 00:45:24,760
and far enough back in time,
889
00:45:24,760 --> 00:45:28,160
scientists found that the biggest stars to ever exist
890
00:45:28,160 --> 00:45:30,650
were born in the very early universe.
891
00:45:30,650 --> 00:45:32,740
If one thinks about the early universe,
892
00:45:32,740 --> 00:45:35,620
then you also discover possibilities
893
00:45:35,620 --> 00:45:38,703
of really pushing star formation to the extreme.
894
00:45:42,467 --> 00:45:44,310
Professor Volker Bromm
895
00:45:44,310 --> 00:45:46,240
has built theoretical models
896
00:45:46,240 --> 00:45:47,450
that show just how big
897
00:45:47,450 --> 00:45:49,093
these early stars could've been.
898
00:45:50,140 --> 00:45:51,810
His visualization lab
899
00:45:51,810 --> 00:45:53,990
simulates how massive clouds of gas
900
00:45:53,990 --> 00:45:55,930
in the early universe collapsed
901
00:45:55,930 --> 00:45:58,050
to form giant stars.
902
00:45:58,050 --> 00:46:00,320
So there are special regions in the universe
903
00:46:00,320 --> 00:46:01,420
where conditions arrive
904
00:46:01,420 --> 00:46:04,067
that you can have extraordinary large
905
00:46:04,067 --> 00:46:06,006
clouds of primordial gas
906
00:46:06,006 --> 00:46:08,573
collapsing in one go if you like.
907
00:46:10,138 --> 00:46:13,150
So then we have a very, very extreme case
908
00:46:13,150 --> 00:46:14,230
of visualized star formation.
909
00:46:14,230 --> 00:46:17,512
A million solar mass cloud collapsing in one go.
910
00:46:17,512 --> 00:46:19,570
And again, this is a very special condition
911
00:46:19,570 --> 00:46:21,540
and we believe this only could've happened
912
00:46:21,540 --> 00:46:22,640
in the early universe.
913
00:46:24,493 --> 00:46:27,040
Volker's work tells us
914
00:46:27,040 --> 00:46:28,870
that back in the early universe,
915
00:46:28,870 --> 00:46:30,020
there may have been stars
916
00:46:30,020 --> 00:46:32,603
a million times more massive than our own,
917
00:46:33,630 --> 00:46:37,063
far, far bigger than anything around in the modern universe.
918
00:46:39,830 --> 00:46:42,603
Our sun would just be speck compared with this.
919
00:46:50,020 --> 00:46:51,940
The question is could the Earth
920
00:46:51,940 --> 00:46:53,930
survive orbiting a star
921
00:46:53,930 --> 00:46:55,760
that is possibly the biggest object
922
00:46:55,760 --> 00:46:56,933
that has ever existed?
923
00:46:59,529 --> 00:47:00,917
Let's find out.
924
00:47:04,820 --> 00:47:09,000
As the sun grows to the size of a super massive early star,
925
00:47:09,000 --> 00:47:10,963
it would envelope the inner planets.
926
00:47:13,435 --> 00:47:16,543
So the Earth needs to move to a safe distance.
927
00:47:23,680 --> 00:47:26,650
To the outer edge of our solar system,
928
00:47:26,650 --> 00:47:28,173
far beyond Neptune.
929
00:47:30,340 --> 00:47:31,680
Then we would have our planet
930
00:47:31,680 --> 00:47:33,350
sitting our at this huge distance
931
00:47:33,350 --> 00:47:34,183
and you can also ask then
932
00:47:34,183 --> 00:47:36,200
how long would then one orbit take?
933
00:47:36,200 --> 00:47:37,230
And then you would calculate
934
00:47:37,230 --> 00:47:39,713
that one orbit would roughly take 30,000 years.
935
00:47:42,090 --> 00:47:44,290
Not great for getting birthday presents.
936
00:47:44,290 --> 00:47:45,280
And New Years Eve
937
00:47:45,280 --> 00:47:46,620
would be something to be enjoyed
938
00:47:46,620 --> 00:47:49,497
only once every 1,200 generations.
939
00:47:49,497 --> 00:47:51,670
But there's a twist in this tale
940
00:47:51,670 --> 00:47:53,893
that means none of that really matters.
941
00:47:54,992 --> 00:47:56,332
The big problem then
942
00:47:56,332 --> 00:48:00,020
that such a hypothetical planet would encounter
943
00:48:00,020 --> 00:48:01,830
is that the host star,
944
00:48:01,830 --> 00:48:05,920
the supermassive star would have a very short lifetime
945
00:48:05,920 --> 00:48:09,240
because our sun lives for another five billion years.
946
00:48:09,240 --> 00:48:12,460
But the total lifetime of the supermassive stars
947
00:48:12,460 --> 00:48:14,030
is just a few hundred thousand years,
948
00:48:14,030 --> 00:48:15,630
maybe up to a million years.
949
00:48:15,630 --> 00:48:18,010
So this is in astronomical terms,
950
00:48:18,010 --> 00:48:19,283
a blink of an eye.
951
00:48:21,708 --> 00:48:23,330
Put simply,
952
00:48:23,330 --> 00:48:26,203
if our sun had been a massive early star,
953
00:48:26,203 --> 00:48:29,053
life as we know it would never have existed.
954
00:48:34,140 --> 00:48:36,450
Before life had a chance to evolve,
955
00:48:36,450 --> 00:48:38,280
the star would come to an end,
956
00:48:38,280 --> 00:48:40,963
perhaps in a most spectacular way.
957
00:48:44,790 --> 00:48:48,800
If these early super stars were to explode,
958
00:48:48,800 --> 00:48:49,633
the supernova explosion,
959
00:48:49,633 --> 00:48:52,496
then we could say that these would be the biggest explosions
960
00:48:52,496 --> 00:48:55,040
ever to happen in the history of the universe
961
00:48:55,040 --> 00:48:55,873
since the big bang.
962
00:48:55,873 --> 00:48:56,706
The big bang, of course,
963
00:48:56,706 --> 00:48:57,950
would still beat everything else.
964
00:48:57,950 --> 00:48:58,783
But otherwise,
965
00:48:58,783 --> 00:49:01,643
those would be truly colossal explosions.
966
00:49:05,200 --> 00:49:08,020
In their lives and even in their deaths,
967
00:49:08,020 --> 00:49:09,337
these giant early stars
968
00:49:09,337 --> 00:49:10,630
were the limit,
969
00:49:10,630 --> 00:49:13,750
the very end of the scale of big.
970
00:49:13,750 --> 00:49:16,243
But they just don't work for planet Earth.
971
00:49:17,100 --> 00:49:20,050
We've tried changing the size of the planet,
972
00:49:20,050 --> 00:49:21,313
the size of our sun,
973
00:49:21,313 --> 00:49:23,750
and even the size of living things
974
00:49:23,750 --> 00:49:26,080
but nothing works quite as well
975
00:49:26,080 --> 00:49:27,303
as what we started with.
976
00:49:32,270 --> 00:49:34,760
We are our size.
977
00:49:34,760 --> 00:49:38,403
Change it, and we risk changing who and what we are.
978
00:49:39,560 --> 00:49:42,010
So does size matter?
979
00:49:42,010 --> 00:49:42,963
What do you think?
980
00:49:43,830 --> 00:49:45,410
It matters hugely
981
00:49:45,410 --> 00:49:47,540
and it depends on what you're looking at.
982
00:49:47,540 --> 00:49:49,984
If you're looking at the brain, yes.
983
00:49:49,984 --> 00:49:52,793
If you're looking at bodies,
984
00:49:52,793 --> 00:49:57,700
just sustaining life in different thermal habitats,
985
00:49:57,700 --> 00:50:00,413
so size matters tremendously.
986
00:50:03,220 --> 00:50:04,970
Size doesn't matter.
987
00:50:06,020 --> 00:50:07,690
I've met the shortest people in the world
988
00:50:07,690 --> 00:50:09,967
and also some of the tallest.
989
00:50:09,967 --> 00:50:13,884
(speaking in foreign language)
990
00:50:16,270 --> 00:50:18,550
I even once met something taller than me.
991
00:50:18,550 --> 00:50:19,400
It was a giraffe.
992
00:50:22,160 --> 00:50:25,000
Today, Ian and Stuart produced a pumpkin
993
00:50:25,000 --> 00:50:29,595
weight 2,252.3 pounds.
994
00:50:29,595 --> 00:50:31,771
That's a new UK record.
995
00:50:31,771 --> 00:50:32,604
Woo!
996
00:50:33,940 --> 00:50:35,576
Size is the only thing that matters.
997
00:50:35,576 --> 00:50:36,923
Don't have to be pretty,
998
00:50:36,923 --> 00:50:38,170
don't have to look nice.
999
00:50:38,170 --> 00:50:39,770
Only thing that matters is size.
1000
00:50:42,620 --> 00:50:45,240
So size definitely matters for the redwood forest.
1001
00:50:45,240 --> 00:50:49,740
I think it really creates the structure, the scaffolding,
1002
00:50:49,740 --> 00:50:51,110
that makes the redwood forest
1003
00:50:51,110 --> 00:50:53,700
such a beautiful place to spend time.
1004
00:50:53,700 --> 00:50:56,010
So despite what some believe,
1005
00:50:56,010 --> 00:50:58,303
bigger isn't always better.
1006
00:50:59,570 --> 00:51:01,388
Bigger is hotter,
1007
00:51:01,388 --> 00:51:02,483
weaker,
1008
00:51:04,270 --> 00:51:05,363
more dangerous.
1009
00:51:06,840 --> 00:51:08,410
Bigger is grander,
1010
00:51:10,930 --> 00:51:11,763
slower,
1011
00:51:13,976 --> 00:51:15,559
and more fantastic.
1012
00:51:16,457 --> 00:51:19,777
And size really does matter.
1013
00:51:21,225 --> 00:51:24,142
(planet exploding)
1014
00:51:29,687 --> 00:51:32,520
(uplifting music)
75119
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