Link to comic: https://xkcd.com/2821/
this post was submitted on 29 Aug 2023
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and I thought this had to do with light refraction lol
It does: Light does not follow the path of minimal distance between two points, but the path of minimal time. This is called Fermat's principle.
Because water has a higher refraction index than air, light is slower in it and therefore takes a longer time to travel through it. Thus, it takes less time to take a longer path that spends more time in the air.
Fun fact: The underlying law of this principle is the principle of least action. This is the most basic law of nature we know of and can be used to derive all of physics.
So... Nature is lazy?
I'd add to this that, if I'm not mistaken, it's because light takes all possible paths and the average measured time is longer
The probability of a path it takes is the sum of all possible paths. Richard Feynman uses this exact swimmer in the water example during one of his lectures of physics.