Water Defies Gravity?! Air Pressure Science Experiment

How does a full cup of water stay upside down without spilling? It sounds impossible, but thanks to air pressure, it's totally possible! Here's how it works:

When you fill the glass to the very top and cover it with a card, the water creates a tight seal against the card.
The air pressure in the room pushes up on the card with more force than gravity pulls the water down.
This delicate balance keeps the water inside—until a tiny bit of air sneaks in. Then? SPLASH!

This simple yet amazing experiment demonstrates just how powerful air pressure can be! Try it at home with just three everyday items:

✔ A cup or glass
✔ Water (fill it ALL the way to the top!)
✔ A sturdy card (a playing card or index card works great)

Science in action! This is the same principle behind how airplanes fly and why we feel pressure changes on an airplane or underwater. Air is constantly exerting force all around us—even when we don’t realize it!

Would you try this experiment?