The physics of surfing - Nick Pizzo
Whether or not you realize it,
as a surfer you’re a master
of complicated physics.
The science of surfing begins
as soon as you and your board
first hit the water.
The board’s size and light construction
help it displace a lot of water.
In turn, a buoyant force
equal to the weight of the
displaced water pushes up,
counteracting you and your board’s weight.
This lets you stay afloat while
you wait to paddle for a wave.
And what exactly are you waiting for?
The perfect wave, of course.
Like other waves in physics, ocean waves
represent a transfer of energy.
Wind blowing across the ocean accelerates
water particles near the surface,
leading to the growth of ripples
that become waves.
These deviations from the flat surface
are acted upon by gravity,
which tries to restore the surface
to its original flat state.
As the waves then move through the water,
particles push and pull on their neighbors
through the wave induced pressure,
and this motion propagates energy through
the water in unison with the wave motion.
The motion of these particles
is much more limited than the
overall motion of the waves.
Near the shore,
the shallower seafloor constrains
the motion of the waves
to occur in a more limited region
than out at sea,
concentrating the wave energy
near the surface.
If the topography of the shoreline
is even and smooth,
this will refract the waves
to become more
parallel to the shore as they approach.
This is the crucial moment.
As the wave gets near,
you quickly pivot your board
in the same direction as the wave
and paddle to match its speed.
Your board forms an angle with the water,
and this creates a dynamic pressure
on the bottom of it,
forcing you and your board
out of the water,
to skim along the surface.
At the same time,
your increased forward momentum
makes you more stable,
allowing you to stand up
and surf along the wave.
Now you’ve caught the wave,
and are riding along its front
face parallel to the shoreline.
Fins on the surfboard allow you to alter
your speed and direction
by repositioning your weight.
Above you is the wave’s crest,
where the water particles are undergoing
their greatest acceleration.
That forces them to move faster
than the underlying wave,
so they shoot ahead before falling under
gravity’s influence.
This forms the waves’ characteristic
curls, or jets,
as they break along the shore.
Sometimes, the curl might completely
enclose part of the wave,
forming a moving tube of water
known as the barrel.
Because of irregularities in the seafloor
and the swell itself,
few barrels last as long as the legendary
27-second ride off the coast of Namibia.
But many who manage to get barreled
have said they feel time
passing differently inside,
making it one of the most magical
experiences a surfer can have.
Of course,
not all beaches are created equal.
Offshore underwater canyons or rock
formations
in certain locations like Nazare, Portugal
or Mavericks, California
refract the incoming wave energy
into a single spot,
creating massive waves
sought by surfers worldwide.
And some of these waves travel
for more than a week,
with swells originating more than 10,000
kilometers away from shore.
Waves surfed in sunny California
may have originated in the stormy
seas near New Zealand.
So while you may not be thinking about
weather patterns in the South Pacific,
tectonic geology, or fluid mechanics,
the art of catching the perfect wave
relies on all these things and more.
And the waves we surf, created by wind,
are just one visible part of the
continuous oscillation of energy
that has shaped our universe
since its very beginning.
