Water is all around us; it makes up almost two-thirds of the planet's mass, but one interesting about water is what it can do to light.
Water has refractive properties, which means it can change the appearance of light and create the optical illusion that something is actually backwards when it's not.
In this video experiment, you will see the cup of water appear to reverse an arrow on a piece of paper.
Pretty cool, huh? Try this with your kids and see what they think!