Why & How do I see this heart-shaped cardioid formed in my cup

Ok, first of all if you don’t know what I’m talking about, I’m talking about this shape in a cup of tea/coffee (or even water). I first got curious about this weird shape appearing in my cup a few…

Cardioid - Wikipedia

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Cardioid - Wikipedia

All stories published by The Startup on February 06, 2020 – Medium

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Cardioids in coffee cups - Chalkdust