This is commonly represented on a graph with physical locations along the horizontal axis and time running vertically, with units of formula_1 for time and "ct" for space. Light cones in this representation appear as lines at 45 degrees centered on the object, as light travels at formula_2 per formula_1. On such a diagram, every possible future location of the object lies within the cone. Additionally, every space location has a future time, implying that an object may stay at any location in space indefinitely.