It’s kinda hard to explain, but when a drop of blood hits the water, it becomes a ring instead of just a red splatter. Why is this?
In: Biology
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This is not exclusive to blood or to falling into water. The issue is that a falling droplet of fluid has momentum in every portion of the fluid. When the droplet hits a fluid or surface what it is hitting doesn’t want to get out of the way so the fluid deflects, sliding along the surface until friction stops it.
The fluid can’t flow through itself so the net effect is flowing outward from the center. But remember that *all* of the fluid has momentum so fluid in the middle doesn’t want to just stop dead in place after impact. It still needs to shed speed which means it too will move away from the center.
Overall this means that if you drip even water onto the floor it tends to form a ring.
When blood hits water, some of the blood gets propelled out tangentially, so it sort of “spills out” along the surface. This is because the blood in the centre of the droplet has to spend its energy to push the blood surrounding it out of the way in order to flatten out. This creates a little wave in all directions, therefore a ring from the centre.
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