The special function of black coffee: forecast the weather

On a rainy day, drop a sugar cube into a black coffee and observe the bubbles released by the dissolution of the sugar cube without stirring. If the bubbles are concentrated in the center, the pressure is high and the weather will clear up soon. Bubbles attached to the glass indicate low air pressure, either heavy rain or heavy snow. The surface tension created by the fat of coffee beans is a key factor in determining the location of bubbles.

Climate factors, except air pressure, temperature and humidity, should have the same effect on the cup everywhere. The oil-water emulsion system in the cup should also be uniform. The surface tension varies only at the contact surface with the cup wall. Then the location of the bubble should have less to do with climate and more to do with cups. If the glass is washed clean, there is no residual oil, according to the hydrophobicity of bubbles, it should be away from the wall of the cup.