{"id":68364,"date":"2026-10-12T05:29:33","date_gmt":"2026-10-11T20:29:33","guid":{"rendered":"https:\/\/phys-edu.net\/wp\/?p=68364"},"modified":"2026-10-12T05:29:33","modified_gmt":"2026-10-11T20:29:33","slug":"we-live-at-the-bottom-of-an-ocean-of-air-a-plastic-bottle-experiment-reveals-the-truth-about-air-pressure-a-high-school-physics-refresher-for-adults","status":"publish","type":"post","link":"https:\/\/phys-edu.net\/wp\/?p=68364&lang=en","title":{"rendered":"We Live at the Bottom of an Ocean of Air! A Plastic Bottle Experiment Reveals the Truth About Air Pressure (A High School Physics Refresher for Adults)"},"content":{"rendered":"

Hi, I’m Ken Kuwako, your friendly Science Trainer. Every day is an experiment!<\/strong><\/span><\/p>\n

\u3010This article is also available as a radio episode!<\/a>\u3011<\/p>\n

Quick question: do you have a pencil nearby? If so, let’s try a little experiment. Pinch the pencil between your two index fingers, one on each end, and press them together. How does it feel? Which finger hurts more, the right or the left?<\/p>\n

If you think about balanced forces and Newton’s third law, both fingers should be feeling exactly the same amount of force. And yet the finger on the sharp tip hurts way more. Same force, so why does it feel so different? The answer lies in a wonderfully magical idea that governs everything from our daily lives to the workings of the universe: pressure<\/strong>.<\/p>\n

The Pressure Formula: How Force and Area Work Together<\/h3>\n

The answer is simple: the force is concentrated on a tiny area. To compare the effect of forces fairly, we need to look at them over the same amount of area, and that is exactly why the concept of pressure<\/strong> was born. Pressure is the amount of force acting on every 1m^2<\/strong>.<\/p>\n

P = F\/S<\/p>\n

(Pressure = Force \u00f7 Area over which the force acts)<\/p>\n

Pressure is measured in Pa (pascals)<\/strong>. Let’s try it with our pencil. Say you’re pressing with a force of 0.1N (about the weight of a 10g object) and compare the areas.<\/p>\n

Left finger (flat end: 0.5cm^2):<\/p>\n

P_left = 20,000 Pa<\/p>\n

Right finger (sharp tip: 0.01cm2):<\/p>\n

P_right = 100,000 Pa<\/p>\n

That means your right finger is under 50 times more pressure<\/strong> than your left! No wonder it hurts!<\/p>\n

We’re Deep-Sea Fish at the Bottom of an Ocean of Air!?<\/h3>\n

Now let’s talk about pressure on a much grander scale. Right now, we’re all living at the bottom of an atmosphere that wraps around the Earth and stretches over 150km high. Just like fish living at the bottom of the sea, we’re basically deep-atmosphere creatures<\/strong>. Above our heads, 150km worth of nitrogen, oxygen and other air molecules are piled up. Each one is light, but when you stack up that many, the total weight is staggering. The pressure created by this weight is atmospheric pressure<\/strong>. The average pressure at ground level is about 1,000hPa (hectopascals)<\/strong>.<\/p>\n

“Hecto” means 100 times, so that’s equal to 100,000Pa<\/strong>. In other words, a force of 100,000N (about 10 tons!) is pressing down on every 1m^2<\/strong>. Hard to picture 100,000N, right?<\/p>\n

Think of it in milk cartons (1kg \u2248 10N). It’s like lying down with 10,000 milk cartons<\/strong> stacked on top of you. Just imagining it makes you feel squashed, but we stay in balance by pushing back from the inside with the same force.<\/p>\n

Atmospheric pressure is stronger than you might think. You can even lift a whole desk using just a plastic sheet!<\/p>\n