the tallest roller coaster in the world.

At 139 meters, it's nearly the height

of the Great Pyramid of Giza.

But what if we built a roller coaster even taller?

What if there was a coaster that went as high

as the tallest building on Earth, the Burj Khalifa?

Well, it's a good thing we don't,

because strapping into a ride like that

might be the last thing you ever did.

The true limit of a roller coaster's height has

less to do with engineering and more to do

with the limits of the human body.

Because the higher the roller coaster,

the faster you'll drop under gravity.

And on our 800-meter-tall megacoaster, riders would hit

the blistering top speed of 370 kilometers per hour.

Going this fast, the wind alone would cause serious damage.

For comparison, here's what a wind tunnel

does to a human face.

Matt Calabrese: Your skin would pull back at the cheeks,

your eyes would be seeing a lot of damage

if there was debris in the air or anything like that,

and your ears would probably start popping,

which wouldn't be fun.

Narrator: Some of this is already a problem

for Formula Rossa, the fastest roller coaster in the world.

It reaches a top speed of 240 kilometers per hour.

And anyone who rides it has to wear goggles

to protect their eyes.

Because at those speeds, dust and debris

in the air turn into tiny missiles.

Speaking of missiles, dust and debris

wouldn't be the only problem.

Calabrese: The main thing I'd be worried about is

if you had a bird strike.

Narrator: Yes, a bird strike.

It's rare, but it can happen.

Shane Matus: I was like, oh, my God, oh, my God.

Narrator: At lower speeds, it could leave you

with a bad bruise or a painful welt,

like with the Kingda Ka rider.

But at 370 kilometers per hour,

you, and the unfortunate bird, would likely die

from the collision.

Now, you could just wear a motorcycle helmet

and protective clothing before strapping in.

But there's another problem that no amount

of protective gear could fix:

g-force.

It's the force that makes you feel heavier than normal,

like when you're riding through a coaster loop.

Normally, you experience 1 g-force.

But when you rapidly accelerate,

like when you're going through a coaster loop,

the g-force ramps up,

which causes blood to rush away from your head

and often makes riders feel light-headed.

For this reason, most roller coasters don't subject you

to more than 5 gs, tops.

But we're not talking about your typical coaster.

If you enter a loop on the Khalifa coaster

at more than 300 kilometers per hour,

Calabrese: Blood will start to move away from your head

and to the rest of your body,

and that means you'll start to gray out

and then possibly black out,

and that's not good.

Narrator: So what can engineers do to protect riders

as they continue to build taller, faster coasters?

The boring option is to slow down the ride

by adding breaks along the first drop.

But there's a better, more exciting way

around the problem: loops.

Really big loops.

Calabrese: All we have to do is

manipulate the curvature

to maintain the g-forces that we want.

So, instead of a tight loop that you would see

on a low-speed roller coaster,

you need big, swooping loops

and large-radius curvature to make sure

that you're not generating huge amounts of

g-force at that speed.

And as you go through the roller coaster

and you lose speed due to air resistance

and drag on the wheels, your speed drops

and your curvature will get tighter.

Narrator: That's why many roller coasters start

with one big loop followed by a series

of faster, lighter ones.

So, in theory, our Khalifa coaster is rideable,

as long as we add big enough loops

and hand out protective eye gear.

That said, we'll probably never see a roller coaster

get much taller than they are today.

Because, nowadays, there are cheaper and more efficient ways

to thrill and terrify riders.

For example, hydraulic or magnetic launching systems

accelerate riders to extreme speeds without needing

to build an expensive, giant drop.

So, perhaps the only reason to ever build something

like a Khalifa coaster would be for the view.

Calabrese: I love roller coasters with beautiful views,

and it adds so much to the experience,

having a view on the way up.

So, any beautiful location,

I'd love to see a roller coaster in order

to get a different perspective on those views.