The first similarity theorem (Newton's theorem) states: If a physical phenomenon is described by a differential equations system, it is always possibleTto represent it as a similarity equation If the physical phenomena are completely similar, all quantities characterizing these phenomena must be in certain ratios for similar points and similar moments in time Similar phenomena have numerically identical similarity numbers Those phenomena are similar whose uniqueness conditions are similar and the similarity numbers, compiled from the unique-ness conditions, are numerically equal

The first similarity theorem, also known as Newton's theorem, states that if a physical phenomenon is described by a system of differential equations, it can always be represented as a similarity equation. This theorem also states that if physical phenomena are completely similar, all quantities characterizing these phenomena must be in certain ratios for similar points and similar moments in time. Additionally, similar phenomena have numerically identical similarity numbers, and those phenomena are considered similar if their uniqueness conditions are similar and the similarity numbers, derived from these uniqueness conditions, are numerically equal.