Motion of objects through space takes time. All objects that exist in space are constantly in motion through space. All of these objects therefore also exist in time, and are constantly in motion through time. People and objects on the earth are constantly passing through time, or aging, or evolving. People and objects on the earth move about the earth.
People can walk or run, rocks can slide down a hill or be thrown, etc.
As we look around us, we notice that objects can and do move through space at unequal and changing rates of speed. In the same way, we can now recognize that people, and objects, around us can and do move through time at unequal and changing rates of speed. Although the rate of motion of objects through space is not constant, and although the rate of motion of objects through time is not constant, modern physics recognizes that all objects in the universe move through space-time at the exact same rate of speed. This universally constant rate of motion of objects through space-time is known as the speed of light. According to modern physics, the speed of light is constant throughout space-time.