How many coordinate axes are usually used to describe three-dimensional space? What does the fourth dimension measure?
Solution 9RQ Part 1 In a three-dimensional space, any particle can move in three independent directions. Hence we need three coordinate to unambiguously describe the position of the particle in the three-dimensional space. So we need three coordinate axes to describe the three-dimensional space. Part 2 In the special theory of relativity, space is constituted with three space dimension and one time dimension. Now the first three dimensions are the space coordinate and hence the fourth dimension is the time coordinate. Hence the fourth dimension measures the time.