You know how some stuff floats on water? Pretty cool, right? Okay, well, see you later.
Wait a minute—how and/or why does stuff float, though? If only there were some sort of super-simple experiment that demonstrates how that works.
A Super-Simple Experiment That Demonstrates How That Works
Well, whaddaya know?! All you’ll need are two glass drinking glasses and some water. Non-glass glasses will work, too, but glass glasses are really the best for this demo. Make sure one of the glasses is larger than the other; ideally, the smaller one should fit inside the larger without touching the sides at all. If you find a glass fits inside another glass without touching the sides or the bottom, you may have a poltergeist.
Put just enough water in the larger glass to cover the bottom. Then, set the little glass inside the big one. The idea is that the small glass will float—if it doesn’t at this point, take it out and add more water to the large glass.
Repeat the process. Add more water, as needed, until the smaller glass floats in the water. You’ll probably have to be very careful when setting it in there, as it may tip over while floating. Do it just right and you can balance the little glass so it’s not touching anything but the water.
It’s Science, Not Magic. Jeez!
What just happened there is called “displacement.” When you’ve got the right amount of water in the larger glass, it (the water) weighs more than the smaller glass. Floating objects—be they drinking glasses or a cruise ship—displace an amount of water equal to their own volume.
In this case, “displace” basically just means it pushes the water out of the way until it finds its magical scientific floaty balancing point. Also, it doesn’t have to be water, just whatever liquid the floating object is floating it. Could be chicken broth and it would still work the same. Smaller/lighter objects must displace less liquid to float that larger/heavier ones, obviously.
Serious question: If every boat in the world were taken out of the water, how much would sea levels go down?
- 365 More Simple Science Experiments with Everyday Materials, E. Richard Churchill, Louis V. Loeschnig, and Muriel Mandell, illustrated by Frances Zweifel, 2014. ISBN 978-1579129675.