You Don't Actually Suck a Drink Up a Straw Here's Why

You think you suck a drink up a straw. You don't. You never have, not once.

If your mouth is not pulling the liquid upward, then what is actually doing the lifting here?

When you breathe in, you lower the air pressure inside your mouth and the straw. But the whole atmosphere keeps pressing down on the surface of your drink, about 14.7 pounds on every square inch. With less pressure fighting back from inside the straw, that outside air wins the tug-of-war. It pushes the liquid up into the low-pressure space, climbing toward your lips. Your lungs never pull anything. They just clear the way.

Here is the strange part. Because air does the pushing, there is a hard ceiling. At sea level, even a perfect vacuum could lift water only about 10.3 meters, roughly 34 feet. A straw taller than that? Nothing comes out, ever.

Follow The Explainer Vault — because everything has an explanation.