The equation that relates space and time is given by the spacetime interval, which is a fundamental concept in special and general relativity. The spacetime interval is denoted as Δs and is defined as:
Δs^2 = c^2Δt^2 - Δx^2 - Δy^2 - Δz^2
where c is the speed of light, Δt is the difference in time coordinates, and Δx, Δy, and Δz are the differences in spatial coordinates.
The spacetime interval measures the "distance" between two events in spacetime. It is a quantity that remains invariant for all observers, regardless of their relative motion. The above equation is often referred to as the Minkowski metric or the spacetime interval in the spacetime with signature (-, +, +, +), where the time coordinate has a negative sign and the spatial coordinates have positive signs.
It is worth noting that the equation above relates the units of space and time, but it does not directly provide a conversion factor between them. The conversion factor between space and time is implicit in the speed of light, c, which relates the distance traveled by light in a given time interval.