Take a glass and fill it with water to the very rim. What do you think will happen if you now drop coins into the glass? You think the water will spill over? Let’s give it a try!
Very carefully, without shaking, drop a coin into the glass. Not one spilled drop, right?
Let’s try dropping in another coin. The same result!
Let’s not stop here. Drop in a third coin!
And a fourth!
Into a full glass (200ml) we were able to drop 16 quarters, and not one drop of water spilled over! The water simply expanded at the rim of the glass. In this expansion lies the answer to the riddle–where did the water go that was displaced by the coins. Although the height of the water standing above the rim is much less than the height of a stack of 16 coins, the width of the glass is several times larger than the coins. That means that the surface area of the water is significantly greater than the area of a coin, allowing us to witness this surprising phenomenon. Perhaps you were able to drop in even more coins into your glass!