Surfing is a fun way to pass the time on a hot day, but it’s about more than just balancing on a board. Surfing requires a thorough understanding of science: you must understand how waves travel across the ocean, carrying energy with them, and how you can use some of this energy to propel yourself forward. You’re employing cool science in a really cool way whether you’re surfing or bodyboarding, riding a longboard or zooming on a skimboard. Let’s have a look at it more closely!
The first thing you notice about the water is the waves. Unless it’s a particularly calm day, there are usually waves skimming across the sea’s surface. What are they doing there, exactly? Waves are typically found in areas where energy has manifested. The conservation of energy is a fundamental physics law that states that energy cannot be generated or destroyed; it can only be changed into other forms. Something has to happen to energy when it suddenly arises, concentrated in one spot. Energy doesn’t usually stay put; it tends to spread out in all directions to regions where there isn’t as much.
Consider a few of well-known cases. Assume you’re in the midst of a football stadium and you bang a kettle drum. The drum skin vibrates up and down with kinetic energy as your arm bangs the stick (the energy of movement). Waves of sound energy are created as the drum skin bounces back and forth. These fly through the air, causing air molecules to vibrate in unison, transporting sound energy in all directions until it dissipates and fades away. When you turn on a lamp in the middle of a dark room, something similar happens. Waves of light energy are now emitted from the bulb in all directions. Why can’t you see sound and light travelling like waves on the ocean? Sound travels at speeds of nearly 1000 km/h (600 mph), making it both fast and invisible. Because light travels at a far quicker rate than sound—300,000 kilometres per second (186,000 miles per second)—it transports electromagnetic energy between two locations almost instantly. Even if light may be seen, it cannot be seen travelling.
The waves that wash up on your beach aren’t always generated close by. Walter Munk, an ocean scientist, undertook an astounding set of studies with ocean waves in the 1950s. He was able to demonstrate that certain waves travel almost 15,000 kilometres (9000 miles) across the open ocean before arriving at their final destination. That’s the equivalent of four trips across the United States, from New York City to California! When waves come up on the shore, the more widely separated and cleaner they are, the further they have travelled.
Swell (or groundswell) is the term for these types of waves, and they make the ideal waves for surfing. Groundswell is what causes huge waves to wash up on your beach when there is little or no wind. Wind swell is a term used to describe waves that are formed nearby (by winds blowing in the region). Groundswell is typically choppier, smaller, messier, tougher to surf, and less exciting to surfers. Groundswell and wind swell are often mixed together in a given location, resulting in a random collection of waves that have gone a long distance mixed with waves that have travelled a much shorter distance.