Wealth on Instagram: "This clip shows a perfect mix of motion, inertia, and gravity at work. When the glass is hit, the glass moves before the water does. Water has inertia - meaning it tends to stay in place until a force acts on it. Because the water reacts a split-second later, it rises and spills in that dramatic wave shape. Gravity then pulls the water downward, creating the smooth curve you see as it falls. It looks like magic, but it's just physics: the glass moves quickly, the water lags