Anyone who goes to the North Sea coast to experience the mudflats should be there just before the water runs out. Then an expanse of silt stretches before your eyes, reaching the horizon, which is largely dry and only dotted with individual puddles. Suddenly the color of the mudflat changes over the entire field of view: the water comes. It doesn’t take long before a wide film of water just a few centimeters high pushes itself toward the bank. Once the last gaps are closed, the level gradually rises and it looks like the grandest scene is over.
But after a while, the situation suddenly changed again when the individual waves run towards the shore above the water which is now 10 to 20 cm high. They are strangely stable and nothing can be stopped.
Even when they hit the bridge, they are not lost like ordinary undulating waves, but are reflected on the bank and return to the sea. They keep their shape. Even if they encountered other incoming fronts on their way back, the two of them simply crossed each other. In the encounter zone, individual spikes accumulate for a short time.
It’s amazing that the waves remain so stable over long distances with no apparent outboard motor. We usually experience behavior quite different from everyday life. If you throw a stone into a lake, for example, it creates a local bulge in the water, called a wave packet. It expands on the surface and in the meantime fuses into a well-ordered system of individual rings.
Those with larger wavelengths, that is, as the mountains diverge, precede those with smaller wavelengths. The speed depends on the wavelength. This is why the wave packet diverges in water; This phenomenon is called dispersion. Because of this, compact hikes must actually be broken down into individual components, and hills should not go unflattering and clearly defined like lonely people on a beach.