What Does Coffee Sugar Reveal About Air Pressure?
A sugar cube dropped into hot coffee, left unstirred, can suggest short-term weather. The claim comes from British writer Matthew Cole's book A Cup of Coffee Tells the Weather. If bubbles gather in the center of the cup, pressure is high and clearing is likely; if they gather around the edge, pressure is low and rain or snow may follow.
The effect rests on surface tension from coffee oils and how high and low pressure change it. Not every cup works: instant and pour-over coffee are poor choices. Freshly ground, freshly made hot Americano performs better, and what is coffee sugar matters here, since a cube rather than regular granulated sugar gives the clearest bubble pattern.
From late March to around Qingming, Guangdong often enters a continuous rain mode. The weather forecast says it will rain, but it occasionally clears up when you go out, making it hard to decide whether to bring an umbrella. There is an interesting little experiment circulating: brew a cup of hot coffee, drop in a sugar cube without stirring, and observe where the bubbles gather. This can roughly tell you whether it will clear up or rain soon. This claim comes from British writer Matthew Cole’s book "A Cup of Coffee Tells the Weather." Behind it is actually the surface tension formed by coffee oils and the weather changes under high and low pressure. Of course, not all coffees are suitable. Instant and pour-over are not ideal choices. Freshly ground and freshly made hot Americano is better, and you should use cube sugar rather than regular granulated sugar.
As soon as late March arrives, Qingming follows closely. "A drizzling rain falls on Qingming" is not just a poetic line. Many friends in Guangdong have recently experienced wet, rainy days in succession. Opening the weather forecast, almost the whole week is rain icons, and just looking at it is dispiriting.
But the weather forecast is sometimes subtle: when you actually go out, the sun happens to be nice. Then a侥幸 mentality starts whispering in your ear—"Don't bring an umbrella, you'll be back soon anyway, it won't rain." As a result, before you go far, the sky seems to deliberately oppose you, and suddenly a heavy rain pours down.
When the forecast says rain but you are not sure whether it will rain during the time you go out, you might as well brew a cup of coffee first. Just one cup of coffee plus one sugar cube can help you judge the short-term weather trend.
Using a cup of coffee to guess the weather—this little life tip comes from British writer Matthew Cole’s book "A Cup of Coffee Tells the Weather." The relevant content in the book says: order a cup of coffee, put a sugar cube into the coffee, do not stir, and observe the bubbles released as the sugar cube dissolves. If the bubbles gather in the center, it means the pressure is high and the weather will soon clear up; if the bubbles gather around the edge of the cup, it means the pressure is low, and there will be either heavy rain or heavy snow.
Some friends may feel this phenomenon sounds as mystical as Turkish coffee fortune-telling. In fact, this magical phenomenon has a scientific basis. Coffee beans contain oils, and the oils float on the surface of the coffee to form surface tension. After a sugar cube is put into hot coffee, bubbles are released as it dissolves. The bubbles float on the surface of the coffee liquid and act as a simple barometer.
On the same horizontal plane, if pressure is unevenly distributed, air flows from high-pressure areas to low-pressure areas. Air in higher-pressure areas flows outward horizontally, and the air above high-pressure areas descends. Because atmospheric pressure increases as height decreases, when air from higher up descends, the pressure it receives increases, its volume decreases, and its temperature rises accordingly—that is, PV/T=C from high school physics. The central area of high pressure is not conducive to the formation of clouds and rain, and is often a cloudless sunny day. The reverse is also true.
Do you suddenly feel that drinking a cup of coffee can hide so much scientific knowledge, and even feel a little tempted to try it at home? It should be noted that the reason bubbles can float on the surface of the coffee liquid and act as a barometer is that there are suitable coffee oils. Instant coffee and pour-over coffee are not the best choices. Freshly ground and freshly made hot Americano is the best choice.
In addition, when choosing sugar, the book also mentions using cube sugar rather than ordinary granulated sugar. The reason is that the cube sugar used for coffee has breathable pores between its crystals, which is more conducive to bubble formation when dissolving.
Speaking of this, Coffee Workshop has taken friends through a review of the impact of atmospheric pressure on weather from high school geography. What do you think?
"Right now I just want to open my phone and check the weather forecast! If it says rain, I'll bring an umbrella and stop taking chances!"
Image source: Internet
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The above content is compiled by CoffeeHunters, a coffee news website.
