Knowing a few physics principles may be the most surefire way to impress your friends.
We dug up this simple trick from brusspup’s YouTube channel that you can use to make a bottle disappear — using supplies from your local drug store.
It uses properties of light to trick our eyes into thinking there’s only liquid in a glass that’s actually holding a bottle.
Light travels through air (green arrows) at a faster rate than it travels through the glass walls of the glass and bottle (red dots) or water (blue arrows).
Our eyes are able to see the bottle inside the glass because our eyes can perceive that the light is travelling at a different speed and angle at each of the four intersections of glass and water.
This distorts the image of the pencil behind the glass.
But when you put fill the bottle and glass with glycerin, it looks like the mini bottle isn't even there -- you can see the pencil behind the glass set up isn't distorted at all.
This is because light travels through glass and glycerin at the same speed, so your eyes don't see a boundary where the bottle is, rendering it invisible.
Glycerin is a liquid that is sold at most drugstores as a skin softener and protectant. It used to be made out of animal fats, and was typically recovered as a byproduct of soap. But today it's normally made out of palm kernel oil.
The colorless, sweet liquid can also be used to make nitroglycerin, the explosive ingredient in dynamite.