The seventh wave is always a big one: true or false?

It isn’t encouraging that the relevant research starts off calling this the myth of the seventh wave. Certainly you will be disappointed if you go down to the beach and expect every seventh wave to be, like clockwork, bigger than all the rest. But while the magic number seven is all washed up, the idea of regular patterns in waves has better prospects.

Waves are most complicated things. If physicists are correct then everything around us including this magazine, the light you’re reading it by and the sound you use to call others over to bask in its wit and charm are all waves.

Even confining ourselves to ocean waves doesn’t make things much simpler. They are remarkable, travelling vast distances with ease, moving through solid objects unscathed, and even riding on the backs of other waves.

That’s where the idea of the seventh wave comes from. Waves at sea all have different speeds. After travelling like this for a while they will sort themselves into groups of waves which share similar speeds. These groups are like larger waves, and the wave in the middle rides higher than the rest on the crest of the entire group. The highest wave is higher thanks to all the smaller waves around it.

Because of this, if you stand on the shore of a good sea and you measure the height of the waves coming in, you may find startling regularity. The highest wave won’t always be exactly on time — sometimes as waves enter and leave the group the pattern is disrupted and the big one comes sooner or later — but it won’t be random, either.

The effect is more theoretical prediction than certified fact. It won’t happen all the time, and when it does the average number of waves in each group will depend on the conditions.

So the seventh wave is a myth. Nevertheless, if you go down to the right beach on the right day at the right time under the right conditions you may find that — just for a while — it is true.

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