Tensor analysis is needed to do physics because it allows us to describe the properties of a given physical system in a very concise way. Tensors are mathematical objects that can be used to represent the geometric properties of a physical system. For example, they can be used to represent the shape and movement of objects in space-time. By using tensors, we can avoid having to specify the position and direction of every particle in a system, and instead describe their properties by using just a few numbers. This makes tensor analysis an extremely...