I am on a platform 21 meters above the water.
And today, a bunch of amazing athletes
are going to dive off a pier into the ocean below.
And then after that, I am going to dive off
of some much smaller cliffs behind me.
How in the world can we use science
to keep us safe while doing this?
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So Red Bull invited me to Polignano a Mare, Italy,
for the Red Bull Cliff Diving World Series, to find out.
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The men's diving platform is 27 meters in the air,
and the women's is 21 meters up in the air.
By the time they reach the water,
these divers can be traveling at speeds
up to 85 kilometers per hour.
The divers are scored on three main aspects
of their dive, their takeoff, their position in the air,
and their entry into the water.
And it's that last one that I want to talk about today.
Though they start from different positions, including front
flips, and back flips, and handstands, the divers
all end up in the same position when they enter the water,
vertical, with their muscles tense and their feet down.
But why?
Let's start by talking about deceleration.
When the athletes reach the water
they're going to slow down and stop moving,
and deceleration is a measure of the rate
at which they slow down.
We can look at a simplified formula for acceleration
or deceleration, as the change in velocity
over the change in time.
The velocities the divers are going
at when they reach the water is pretty much
unchanged between dives, they're probably
going around 85 kilometers per hour, and then they stop.
A belly flop results in a sudden stop, and a short change
in time, while a sleek vertical entry position into the water
increases the amount of time it takes the diver
to slow down due to drag and buoyancy,
thereby decreasing the rate of deceleration.
And because force equals mass times acceleration,
or in this case, deceleration, the smaller the deceleration,
the smaller the force that the diver will experience will be.
It's actually the same way that an airbag in a car crash works,
the airbag increases the amount of time
it takes for your body to go from moving to stopped,
thereby decreasing the rate of deceleration
and helping to keep you safe.
The vertical entry also changes how the diver's body displaces
water as they enter, a belly flop
presents a much larger surface area than a foot-first entry.
The larger surface area gives the water a greater area
upon which to resist the diver's entrance to the water,
this increases the force on the diver's body.
A smaller surface area allows them to cut through the water
rather than smacking against it.
And this is really important, even diving correctly,
divers can be exposed to multiple g-forces upon impact.
And if they dive incorrectly, that can increase to 20 to 30
g's, which can do serious damage to body tissue.
Now, there are a lot of other cool aspects of physics
that I'm not covering here, including
the angular momentum of the divers
and the surface tension of the water.
But I put links to discussions of those
in the description down below.
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So when you land you land feet first,
and the goal is to kind of just be in a totally straight line.
You want your shoulders, your hips, and your knees,
and your feet all in a line to get through that water.
When you do it right it feels amazing,
you go straight down, super deep,
and you know that you've just done a great dive.
When you land a little short, it feels like an uppercut
from Mike Tyson.
It sometimes hurts.
Actually, most of the time it hurt the feet.
But when you did a dive and only the feet hurt, it's perfect.
Because if you are less vertical,
like this, it's going to hurt a lot of different place.
Or if you are like on the butt a little, it's going to hurt too.
But when you are right vertical, you kind of
dig that hole with your feet.
Then you fall into that hole, it feel really good.
We're hitting the water at anywhere between 70
to 80 kilometers an hour, and we're slowing down
in a couple of seconds.
So it's really hard to describe.
Sometimes it feels like you're in a washing machine,
you go through and your arms and legs, they go everywhere.
But when you do a nice entry, it's such a nice feeling.
You can hear the sound of your feet hitting the water,
and then all of a sudden it's silent.
So you have the wind and then you
hit the water and everything goes silent, and you go wow.
Now watching these divers actually reminded me
a lot of diving birds.
These are gannets, birds that adopt a very similar sleek,
near vertical body shape to cut through the water
and hunt for fish.
These birds can dive from heights
even up to about 30 meters.
And these birds do some pretty interesting things
to keep themselves safe while they're diving too.
Because they're going into the water head first,
they could seriously injure their necks upon impact
if they're not careful.
I found a really cool study from 2016
that looked at all of the different forces
that these birds endure as they're diving into the water,
and how they keep themselves safe.
I found that the birds contract their neck muscles
before impact, causing their tendons to add stabilizing
tension to the bones of their naturally s-shaped neck,
helping to straighten it out and fix it in place,
to prevent buckling and injury upon impact.
And this muscle tension sounded pretty familiar.
But it's not only about being vertical,
it's really about being strong at this precise moment.
If you are vertical but soft, you're going to hurt yourself.
So it's really to get tense right there,
when we enter through the water like this we are protected.
Our body armor, we build the armor to protect everything
in our body.
For me, I'm always making sure that I'm
squeezing tight my glutes, my bottom, and my stomach.
And then for my upper body, I always try and grab my hands
and kind of push them through the water,
and it naturally tightens your upper body as well.
My biggest tip for entering the water for people
who haven't jumped, is a lot of people when they hit the water,
they kind of want to cringe, they're
like waiting for the water, and they get smaller.
Think about elongating, because that's
going to make you squeeze your muscles tighter,
so then the water is not going to feel as hard.
Because if you're braced and you're tight,
then it's going to feel a lot easier than if you're loose
and then you smack.
And be confident and have fun.
This is amazing, you're going to do this, and just appreciate.
My biggest word of advice would be to enjoy it.
It's going to be scary, but just enjoy it and enjoy
where you are.
So now it was time for my own dive,
and I decided to dive from just about four meters.
It's a little shorter than the 21 or 27 meters
that these professional amazing athletes are doing,
but it was still pretty scary.
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Now I wouldn't say that my entry position
was perfect on the first time.
I did try and elongate, but I might have started a little too
early, and I sat down into that dive a little bit.
But with practice I got a little better on the second one,
and I think the next time I'm in Italy diving off of cliffs
I'm going to be just perfect.
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Go forth and do some crazy, awesome, science things.
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