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How Physicists Can Create Better Surfing Waves
How Physicists Can Create Better Surfing Waves
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0:00
A few surf spots on Earth are so legendary
0:02
that surfers dream their whole lives of catching a wave there.
0:06
Like, there’s Peʻahi in Maui, Hawaiʻi,
0:08
which has one of the fastest and largest waves in the Pacific Ocean.
0:12
It’s so extreme that its nickname is Jaws, after the movie.
0:16
Then there’s Praia do Norte in Nazaré, Portugal.
0:19
It has the largest waves ever surfed.
0:22
These monsters can get 30 meters high and
0:25
don’t even look real in some of the photos of them.
0:28
All of these waves are made by physics, of course.
0:30
And scientists are trying to decode the secrets of exactly how they form.
0:34
Because many of the best surf spots are currently
0:36
threatened by environmental changes.
0:38
And understanding that formula could help scientists preserve them …
0:43
or even allow for us to design some sick waves from scratch.
0:47
[♪ INTRO]
0:50
When you think of a surfable wave, you might picture something like this.
0:54
The top, or crest, of the wave curls over to create what’s called the barrel.
0:58
And when the wave crashes in on itself, you get that foamy whitewater spray.
1:02
Surfers generally surf on the shoulder of the wave in front of the barrel or,
1:07
if they’re skilled enough, in it!
1:09
That’s called getting tubed.
1:10
And while it’s easy to define a wave’s anatomy,
1:12
it’s trickier to say what makes a surfing wave good.
1:15
For one, it depends on the surfer’s skill level.
1:18
And every surfer’s gonna have their own preferences.
1:20
So rather than using language to define a perfect wave,
1:23
scientists use a different tool: math.
1:26
To be clear, they’re not trying to define the singular, platonic ideal of a wave.
1:31
Rather, they want to use math to define a range of waves that surfers deem “good”.
1:35
One approach distills waves into four fundamental parameters:
1:39
the height, defined by measuring the wave from its crest to its trough;
1:42
the length, that’s the horizontal distance of a single breaking wave;
1:46
the peel angle, which is the angle between the crest and the whitewater;
1:50
and the breaking intensity, ranked in one paper
1:53
on a scale from medium to extreme.
1:55
Love that the wimpy waves don’t even get to be in the study.
1:59
We don’t care.
1:59
From here, you can determine a wave’s “surf-worthiness”
2:02
by considering what kinds of surf maneuvers
2:04
are possible for waves created with different parameter ranges.
2:07
And within a “surf-worthy” range of wave parameters,
2:10
scientists can get to work reverse-engineering
2:12
the physics factors that lead to those good waves.
2:15
This is complicated by the fact that waves are kinda like snowflakes:
2:20
no two break exactly alike.
2:22
But waves in the same location with similar formation conditions
2:26
tend to look a lot alike, so scientists can still trace backwards
2:30
to discover the factors that made them in the first place.
2:33
To find these baby waves, we must venture far out to the open ocean
2:38
in super deep water, thousands of kilometers away from shore.
2:41
Now, far from shore, in the deep open ocean,
2:44
water picks up the energy that eventually forms waves.
2:48
Most waves start when wind blows across the water,
2:51
creating small pockets of underwater circulation that slowly march forward.
2:56
This is called trochoidal motion, and it’s also what
2:59
makes buoys or ducks bob on the water.
3:02
Stronger winds, say from a storm, can transfer
3:04
more energy to the water and create bigger waves.
3:07
This is why, when there’s a hurricane that’s like just
3:09
far enough off the coast, surfers will decide to go to the beach.
3:14
Once the waves accrue enough energy, they graduate to swells.
3:17
Swells have a wavelength of about 300 meters.
3:20
That’s like three soccer fields, or like… 100 longboards.
3:23
These swells, with their long wavelengths,
3:26
can actually outrun choppy waves with shorter wavelengths,
3:29
helping them survive the long trek to the nearest coast.
3:32
The fun stuff happens when the swells finally get to the coast
3:35
and hit water that’s about half as deep as the swell’s wavelength.
3:39
So like… 1.5 soccer fields or, like, 50 longboards deep.
3:44
This is probably not helpful.
3:46
When the water gets shallow, the bottom of the wave
3:48
drags along the seafloor and slows down.
3:51
But the top of the wave keeps all its momentum and continues forward,
3:55
which causes it to trip over itself, eventually forming crests that break.
4:00
If we’re lucky, the wave will break in just the right way to be surfable.
4:04
But that depends on the shape of the seafloor, called bathymetry.
4:07
To be surfable, a wave needs a non-zero peel angle.
4:11
Otherwise it’s called a “closeout”, where it breaks all at once.
4:13
To avoid closeouts, the beach needs to be uneven,
4:16
so that one side of the wave breaks first, creating a peel angle.
4:20
This is why so many famous surf beaches are also coral reefs.
4:23
Basically if you want an interesting wave, you need an interesting beach!
4:26
Scientists looked at the bathymetry of 34 locations known to have good surfing
4:31
waves, and they identified the seafloor configurations that created them.
4:34
Then, using computer simulations, the scientists studied
4:37
how these configurations affected wave direction, speed, and shape.
4:42
For example, they found that dips in the seafloor
4:44
can make waves faster or more intense.
4:46
And the angle of the seafloor slope relative to the coast
4:49
can affect whether or not waves travel in the optimal direction for surfing.
4:53
So thanks to that data, scientists have basically solved the mystery of how
4:57
bathymetry leads to good waves.
4:59
But it’s still only one part of the equation.
5:02
To get a great wave, everything else needs to be just right, too.
5:06
That includes wind speed and direction,
5:08
swell period and height, and tide conditions.
5:11
So over time, experienced surfers develop intuition for
5:14
the weather and water conditions that forecast the waves they like.
5:18
But those conditions are rapidly changing,
5:20
as more surf breaks are threatened by rising seas, coastal erosion,
5:24
and coastline development, all of which affect
5:26
the bathymetry and coastline shape.
5:28
A 2017 study found that California, for example,
5:31
could lose 34% of its surf breaks by the end of the century.
5:35
Unfortunately, the same strategies that protect coastlines
5:38
can inadvertently ruin great surf breaks.
5:41
Like replenishing an eroding coastline with extra sediment can
5:44
change the bathymetry enough that waves break in totally unsurfable ways.
5:49
That’s why these mathematical models of surf breaks are so important.
5:52
Scientists can help design interventions that
5:55
preserve both coastlines and surf breaks.
5:57
One way is to arrange special sand bags, rock,
6:00
or concrete into underwater structures that direct sand to settle in certain patterns.
6:05
These structures can reduce erosion to protect the coast and
6:08
shape the bathymetry so that waves break in surf-worthy fashion.
6:12
Narrowneck Reef in Australia tried this strategy in 1999 and got it to work.
6:16
Scientists could even someday use these surf break models to turn
6:19
unsurfable beaches into top-tier surfing destinations.
6:23
For example, Middleton Beach in Albany,
6:25
Australia used to only generate closeout waves on its shores.
6:29
Until July 2025, when the beach debuted an artificial reef.
6:33
They leveraged beach measurements and computer simulations
6:36
to modify the seafloor so that it funnels waves in
6:39
just the right way for them to break at just the right speed.
6:43
These discoveries are certainly making waves in the physics community.
6:47
And while surfers will continue to debate the definition of a “perfect” wave,
6:52
at least now they can format their arguments in mathematical terms.
6:56
[♪ OUTRO]
