Space, time, and spacetime

Operationally, space is that which is measured by a measuring wheel (or surveyor’s wheel) moving along a surface or the equivalent. This is essentially a linear or circumferential measurement, which could also be taken with a rod or rule. Operationally, time is that which is measured by a stop watch or equivalent. This is essentially an angular or oscillatory measurement, which could also be taken with a clock or other repetitious movement.

The measurement of both space and time are through movements that start and stop, either actually or virtually. This means that space and time are delimited by the size of the objects and events that are measured. In contrast, spacetime is not operationally delimited. Spacetime continues as a continuum indefinitely, with objects and events located in it.

This is what is commonly meant when someone asks, What time is it? That is a request to locate something within a continuing continuum. The answer may be in terms of space or time, which is why it is called spacetime. It is also what is meant when someone asks, Where is it located?

Because spacetime continues indefinitely, it must have a conversion factor to relate space and time within it. This is the standard or default speed of travel within spacetime that exists throughout the unknown part of spacetime. If the speed or space and time of something are known, they over-ride this standard or default speed.

Spacetime is a theoretical construct. Space and time are the result of measurements.