Have you ever stood above a river or lake and noticed that the surface has visible "patches"? It looks like the surface has different average wavelengths in some areas, leading to the light being reflected differently (more vs less shiny).
Something has puzzled me for a long time. These patches are quite stable. Their shape changes minimally even over a time of minutes. This is clearly a muh longer timescale than the average wave periods, for both the longer and the shorter waves.
Even further, you would expect that at a spatial scale comparable to the small wavelengths, a small wavelength patches boundary would change quite rapidly. But even that doesn't exactly seem to be the case, as far as I can tell.
I unfortunately don't have a video depicting this.
Here are some possble explanations I have personally ruled out:
Cloud shadows would not create sharp patches
The same holds true for srface structures like poles or trash
At some point I suspected oil patches to be the explanation since boats create these patches in their wake, but it doesn't really make sense that there would be so much oil everywhere.
The best explanation I can think of is that this is just how water waves behaves in regards to the spread of waves and wavelengtg w.r.t. spatial and temporal scales.
Perhaps one could demonstrate this surprising long time persistence of avelength patches in an approximate linear system?
Or could there be some true nonlinear stability effects at play?
EDIT: Note that this question is not one of the following:
- Why are there waves (wind)
- Why does the water look darker and brighter (reflectivity due to waves)
The question is about the surprising persistence and localization of these patches.
The best explanation given so far has been a comment saying it is oil. This being the most likely correct answer shows that this question is different from the above similar ones.
I am still a bit skeptical that the oil would be localized so much.
