The Physics of Surfing (Part Two: Tubes and Barrels)

But why do some waves break as hollow grinding tubes while others crumble more gently and forgivingly? Let’s examine a little wave dynamics in order to assess the situation. Ocean waves are created by wind blowing over the ocean surface, as the kinetic energy of the air is converted into potential and kinetic energy of the water. The biggest and most powerful waves are created in massive storms. As the swells generated by these storms travel over the open ocean, the originally chaotic “victory at sea”-type wave motion is gradually organized into cleaner lines. As with all waves, it is not the actual material (water in this case) that travels any distance through the medium — it is the energy of the wave. As the wave energy passes through a point in the ocean, the water molecules rise and fall in a circular pattern but remain in the vicinity as the disturbance passes by.

Previously: Dude, It’s Physics

The Physics of Surfing (Part One: Dropping In)

[P]addling by itself doesn’t get you into the wave, because you actually cannot paddle as fast as the wave is moving, and you need to match the speed of the wave if you want to ride with it. In order to catch up to that wave speed, it’s necessary to use the gravitational potential energy of the wave. The trick is to obtain sufficient speed by paddling that, as the wave travels under you, your board begins to fall down the face. As you drop down the front of the wave, the gravitational potential energy you gain is converted into kinetic energy. Soon you are travelling as fast as the wave. In fact, if you continue to drop to the bottom of the wave, you’ll be moving faster than the wave — and if you don’t cut into the face, you might temporarily outrun it.