This liquid here is somewhat magic. It's supposed to be hard, but when something solid hits it, it becomes solid. What sort of wizardry is involved?

Non-Newtonian fluid, like the combination of cornstarch and water above, can be impossibly thick. Non-Newtonian fluids include everyday items like ketchup, toothpaste, blood, shampoo, and more. The magic lies in the viscosity.

The Discovery Slow Down explains that the particles in non-Newtonian fluids are so large that when force is applied to it, "they have no time to move, creating a solid". Check it out in the video: