Original subtitles

Gravity, it's one of those weird things in life.

We all kind of know what it is

but we kind of don't as well.

And there's something I've always

found really hard to believe.

400 years ago, Galileo said, "If you drop

"two things of different weights, they'll both

"hit the ground at the same time."

Which doesn't seem to make any sense

because surely the heavy thing would hit the ground first.

So if I weigh 73 kgs and this orange weighs 100 grams

and I jump out of a plane with the orange,

which one is gonna hit the ground first?

In this episode I thoroughly test Galileo's theory

by using a roller coaster to experience gravity

on another planet.

Jeez.

(engine whirring)

Achieve weightlessness without going into space

and then I jump out of a plane with an orange.

(screams)

I've always been fascinated with how the world works

and I've got lots of questions about why things happen.

To find out the answers, I'm gonna blow stuff up.

I'm pretty sure if Galileo was alive today

that he would've wanted to have jumped out of a plane

to test his idea as well.

We tend to think of gravity like this.

(egg splattering)

Stuff falling.

But the law of gravity is way, way weirder

than you could ever imagine.

So I drop this egg and it falls to the earth, right?

Well, not quite, something else happens.

The law of gravity says that both the egg

and the earth are attracted to each other.

That's how gravity works.

Everything is attracted to everything else.

So a large bridge seemed the best place to experience this.

You know that expression, "putting on a brave face"?

Well that's mine, right there.

(Nigel grunting)

People think that stuff falls, stuff like eggs

and in this situation me, but the law of gravity

combined with Newton's third law says that something

way, way weirder is happening.

I might be falling but the earth

is also falling towards me.

(Nigel laughing)

To be fair though, the earth does have

80 billion trillion times more mass than I do.

So it does most of the attracting

and I do most of the falling.

But in a very tiny, tiny way,

the earth also moves towards me.

So if this orange and this apple

were floating in space, then gravity would slowly

start to draw them together.

And as they got closer together, the strength

of gravity would increase until after

about 84.5 hours they'd meet.

The thing which complicates everything is air.

We all know, that if you drop a feather and a coin,

the coin's gonna hit the ground first.

That's true, but it's not the whole story

which is why I'm dropping the coin

and the feather in a vacuum chamber.

Galileo was a really clever bloke.

He worked out two objects of different masses

will fall at the same rate in a vacuum.

With the air pumped out of our vacuum chamber,

the feather and the coin land at exactly the same time.

Whereas when the chamber was filled with air,

the coin landed first.

In what historians think was only

ever a thought experiment, Galileo suggested

if you drop two objects of different masses

off the Leaning Tower of Pisa, a cannonball

and a wooden ball, they'd both hit the ground

at the same time.

But thought experiments are for babies

so I'm gonna test the theory by jumping

out of a plane with an orange

to see who hits the ground first.

The problem is, I'm not gonna be jumping

out of a plane into a vacuum so I've got to figure out

someway to account for air resistance.

The atmosphere is made up of lots and lots of stuff.

And those gases and other bits and pieces

act like a brake, slowing things down.

We call this breaking effect air resistance.

Because I don't have a 10,000 foot high vacuum chamber

to free fall in with my orange, I'm gonna have

to jump out of a plane into the actual air.

Which means first, I'm gonna have to drop

a whole bunch of stuff from this crane

to see what impact air resistance has on falling.

First up, something light compared with something heavy.

Obviously dropping them both at the same instant

is really important so how we're doing that

is compressed air cylinder.

So when I push a button, that fires off two

air operated pistons, it releases both carabiners

at the same time, and they drop at exactly

the same instant.

Fridges aren't exactly renowned

for their aerodynamic qualities.

A match up with this feather pillow

is likely to be a one sided demonstration.

Professor Stuart Bradley knows a lot about gravity,

so he's going to make sure we get the sciency bits right.

My prediction is, that because of the issue

or air resistance, the fridge will hit the ground first.

Which isn't a ground breaking theory per se,

but it should still be ground breaking

in a more literal sense.

All right, so now it's live.

Three, two, one.

(latch snaps)

Whoa.

(fridge smashing)

Scientifically, hurt your thoughts? (laughs)

I think the fridge is out cold.

(laughs)

The pillow ended up about a block down the street,

while the fridge definitely hit the ground first.

So what does this tell us?

The two main factors affecting the outcome

of this contest were the weight of the fridge

and the aerodynamic qualities of the pillow,

which was more effected by air resistance

relative to its weight so it fell slower.

Now let's drop two objects with similar aerodynamic

qualities just like Galileo's Leaning Tower experiment.

An oversized tennis ball and a bowling ball.

They're both round and about the same size,

so I'm expecting they'll handle air resistance

in a similar manner.

The difference is the bowling ball weighs a lot more,

therefor the smart money has the bowling ball

landing well before the tennis ball.

So three, two, one.

(latch snaps)

I was right (balls crashing) but not by much.

(laughs)

Now we know what happens to a bowling ball, don't we?

Never drop a bowling ball off a crane.

(laughs)

Turns out the bowling ball and tennis ball

were fairly different.

The bowling ball was heavier and the fuzz

on the tennis ball created more air resistance

than the smooth surface of the bowling ball

so it landed a full two seconds later.

But what about me and my orange?

What might happen to us as I jump from a plane?

Time to drop a dummy me and a real orange

from a crane to find out.

Because I've never jumped out of a plane before,

you don't have to jump in tandem so we've added

some diving weights to our dummies to bulk

them up to 162 kgs to match the combined weight of me

and the tandem master.

If it will weigh over 1000 times more than the orange,

we need to get some idea what difference

air resistance makes to see if this is even

going to be possible to film.

Three, two, one.

(latch snaps)

Oh.

See I'm not thinking about this experiment,

I'm thinking about the actual

jumping out of a plane at this point.

(dummies crashing)

Interestingly, the 100 gram orange, having a dimpled

surface with aerodynamic qualities closer

to our bowling ball than our tennis ball,

fell almost as fast as the 162 kg dummies did.

Which makes me hopeful we can actually film this.

Next I use a rollercoaster to see what gravity

feels like on different planets.

I've got a twisty twisty (laughs).

And dodge it at 5000 feet.

Gravity's a constant so unlike us it never rests.

And that also means that it effects us

in all kinds of interesting ways.

So in the morning

I'm this tall.

But when I return home at the end of the day

what I find is that I'm now about a centimeter shorter.

And that's because over the course of the day,

the mass of my body has been attracted

by the gravitational pull of the mass

of the earth and I've shrunk.

And it's not until nighttime when I lie down

and let my spine stretch out that I return

to my normal height.

Try the experiment yourself if you'd like.

The earths mass is six billion trillion tons

which is why it's gravitational pull is so strong.

But gravity is both powerful and weak

because this small magnet is strong enough

to overcome the earths gravity and stick to the lamp.

At small scales like our magnet, gravity is very weak

when compared to other forces like magnetism.

But the bigger an object gets

the more important gravity becomes.

And once an object is very, very big like the earth,

gravity eventually wins out over all other forces.

You can see this when you jump or kick a ball.

It's easy to get a ball flying through the air

but it's much, much harder to get the ball into space

because gravity is constant and relentless.

With the help of an app developed

by the University of Auckland I want to demonstrate

that anything, whether it be a bullet

that you've just fired from a gun or a ball

that you've just kicked, falls towards the earth

at a constant rate of 9.8 meters per second squared.

That sounds strange but it's true.

The app cleverly shows us that what we think

we see happening, isn't.

It looks like the ball is accelerating upwards

but the app shows its vertical speed

is actually decreasing.

When it reaches the top of the arch,

the vertical speed becomes negative as the ball

starts to fall back to the ground.

The graph shows the ball accelerates downwards

at a constant rate the whole time.

Which means me and my orange will as well.

And it must be true because the app said it is.

(electronic music)

I know what gravity feels like here on earth

but what about on a much bigger planet

or a much smaller one?

Here on the earth, we call our everyday gravity one g.

But what does it feel like when gravity's increased

to say, two g on a bigger planet, or less than one g

on a smaller one.

What I need is a machine that manipulates

my experience of gravity.

Something with a lot of acceleration

and deceleration as well a device for measuring

how many gs I'm experiencing.

Well luckily for me, such a machine already exists,

the Rainbow's End rollercoaster.

With kitted my seat out with an accelerometer.

The small steel ball moves on a spring inside the tube

and we'll be able to see it move up and down

as the g forces change.

Basically a rollercoaster is a simple machine

that uses gravity.

So what happens, as you're going up the noisy part

you're storing gravitational energy.

The higher you go the more energy you're storing

and at the top, gravitational energy turns

into kinetic energy which is the fun stuff.

The up shot of all the twisting and turning

is that my experience of gravity changes.

Less than one g, all the way up to four gs,

which is about twice what I'd feel on Jupiter.

That's about two and half back to one.

(electronic music)

I've got a twisty twisty (laughs).

Somewhere on the way back up to the top

of the rollercoaster after about my 20th circuit

and feeling a little like a 10 year old

who's eaten one too many hot dogs,

the novelty and wonder of gravity wore off.

I started to wonder instead if there was a way

escape gravity for a while.

Next I use a converted jumbo jet

to allow be it astronauts to experience weightlessness.

It's pretty simple really.

The jet climbs at a really steep angle,

it levels off and then dives, creating a path

called a parabolic arch.

Now this isn't America, and we don't have a NASA.

So instead, I'm going to achieve weightlessness

in this little puppy.

Head goggles inside.

Get these locked.

This is Wayne Ormrod, he's an aerobatic pilot.

He does this stuff all the time.

(engine whirring)

His plane is called a Racing Robin.

And while it might be little, it's capable

of speeds in excess of 300 kilometers per hour

and is able to fly anywhere from minus three gs

to six gs, which makes the rollercoaster sound timid.

He's confident now, that in between all the swooping

and diving, we can experience weightlessness.

(engine whirring)

A parabolic arch is pretty simple.

Robin climbs fairly high, dives steeply to build up speed

and then loops up in a flight path

called a parabolic arch.

NASA do this in a jumbo jet at 30,000 feet.

We're a lot closer to the ground here

which adds to the anxiety but as promised,

when the wee Robin goes over the top of the arch,

I experience what feels like weightlessness.

I brought a clear globe filled with water

to show the effects of gravity.

We haven't escaped gravity but momentum

of our flight path makes it feel like we have.

It only lasts a few seconds, but it's magic.

Enough of all this mucking about

with orbs of floating water and levitating frogs.

No matter how cool it might be,

it's time to try out our orange.

(uplifting music)

Even if only for a moment or two, the orange,

the plane and I all hang suspended above the earth.

(engine whirring)

So Galileo's famous thought experiment

is looking pretty sound.

But I didn't get where I am today by thinking

so it's time to put all the science to the test,

ignore that nibbling voice saying, "I'll die"

and jump out of a plane.

(Nigel screams)

(electronic music)

Galileo was a clever man.

He theorized if you drop two objects

with different masses, a cannonball and a wooden ball,

off the Leaning Tower of Pisa, they'd fall at the same rate.

My plan is to push his thought experiment

into the 21st Century by throwing myself

out of an airplane with an orange at 12,000 feet.

Along the way, I've tested the law of gravity

to its extremes.

From experiencing all too brief moments

of weightlessness in a stunt plane,

to being squashed down on my seat under four gs

of force on a rollercoaster.

I've had a twisty, twisty (laughs).

What I can't stop thinking about though

is if the orange and I hit the ground

from a great height, then I'll be dead.

So I'm going to need a parachute,

but I've never parachuted or free fallen before

so to prove Galileo right, I'm also going to need

a tandem jump master.

I'm here in Taupo because it's time

to jump out of a plane with my orange at 12,000 feet.

Perfect, start those legs.

It's a bit Biggles isn't it?

I feel like I should be flying Sopwith Camel.

I have to confess at this point

that I said I'd never do a parachute jump

because I've always been convinced the parachute

wouldn't open and I'd die.

Still, here we are.

According to the experts, this is a complete

waste of time.

What's more likely to happen, is the orange

will take off and never be seen again.

But if Galileo and I have one thing in common,

it's stubbornness.

And like Galileo said, "In questions of science

"the authority of 1,000 is not worth

"the humble reasoning of a single individual."

Good enough for me.

The hardest thing about this, is that when

we jump out, I'm holding the orange

and my brain is gonna be telling me

to squeeze whatever's in my hand really hard

because that's the only thing stopping me from falling.

(laughs)

And I know that's dumb, but I know that's

what my brain will say.

And this won't work if I crush the orange.

(engine whirring)

All I can think about at this point is falling and dying.

(suspenseful music)

So we're jumping at twelve?

When we reach 12,000 feet, I'm leaving

this perfectly nice plane and all the way down,

when the parachute fails I'll be telling myself

that I knew this was going to happen.

Still, no backing out now.

(suspenseful music)

The feeling when you first jump is mind blowing.

Here we go,

it's floating.

Just like in the plane, it actually looks

like the orange is floating.

Incredibly, and against all hope,

we all hang together in midair.

And suddenly, I'm not thinking about dying,

I'm thinking about Galileo and gravity

and how science lets us understand things

like the oddly beautiful sight

of an orange falling from 12,000 feet.

My tandem jump master and I

are putting up too much air resistance

to fall quite as fast as the orange,

but our cameraman is able to change

his body position, reduce his air resistance

and save the orange from a splattery death.

(uplifting music)

It's flawless, genius.

That was everything It caught us.

(laughs)

That was really good.

Our experiment has been a complete success.

Turns out Galileo was right, who would've guessed?

My tandem master and I, have a combined weight

of 162 kilograms yet we fell at the same speed

as a piece of fruit, one and half thousand times

lighter than us.

It seems to defy all logic, so what happened?

Well, this illustrates one of the weird things

about gravity.

The weight, or mass, of me and the orange

isn't the deciding factor.

It's the mass of the earth that counts.

All those billions of trillions of tons

exert the same power of attraction over me

as it does to my orange.

So gravity's a complicated but elegantly simple thing

because basically what we've seen is that

if you account for mass, which is pulling you down

and wind resistance which is pushing you up,

then two objects of quite different weight

can fall at pretty much the same speed.

Me and my orange.

But mostly I think we've just proven

that Galileo was a genius.

(uplifting music)