[Kind of crappy visual aid](https://i.imgur.com/zrzlYkW.jpeg)
I’m sitting in my car, procrastinating going inside because of the rain, and I noticed that the rainwater is behaving differently depending on the area where the windshield wipers passed and where they haven’t.
Why is that?
In: 91
Water is cohesive, meaning that it likes sticking together, which is how you can fill a glass slightly above the top and the water will form a curved bubble rising above the glass.
The water on your windshield is just droplets, separate little drops that stick together. That’s why they don’t just immediately run down the windshield as a bunch of little rivers. They’re sticking together as droplets. When you wipe them, the droplets all get pushed along together and combine, and even though a lot of that water gets flicked away, you’ve now added water all along the path of the blade.
Not *a lot* of water, very little, but enough so that any water that falls onto that area doesn’t need to stick together as a droplet. Because that new water gets to stick to all the water molecules already spread across the windshield by your wiper blade, so it just spreads itself out nice and comfy.
To put it in simpler (although not at all ELI5) terms, compare masturbating alone to being at an orgy. When you’re masturbating alone, you’re staying in one spot, but when dropped into an orgy you’ll make your way all around the room and have a great time.
TL;DR the water where your wipers pass are having an orgy before the wiper comes back.
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