According to the model, in a flat universe, the total density is equal to 1. Next, the team must determine the amount of matter in our universe. The amount of matter is determined by measuring the overall height and pattern of the temperature fluctuations. These fluctuations are analogous to ripples in a lake. The kind of ripples I get depends on what the lake is made of. A lake of water will give different ripples than a lake made of mercury.