Time dilation defined Time dilation is the slowing of time as perceived by one observer compared with another, depending on their relative motion or positions in a gravitational field.

For example, the friction between our feet and the ground allows us to walk and drive each day. Friction Friction is defined as the resistance to relative motion between two bodies of contact. The ...

Even though our local group moves at some ~600 km/s relative to the leftover glow of the Big Bang, we cannot feel it, since there's no relative motion or force between our bodies and Earth's motion.

The concept of ‘ to and fro’ motion in a straight line, is also an extension of the concept of relative motion between two bodies Example: Two racing cars have a relative speed of 12 km per hour.

By combining data from the two, Hand et al. were able to detect the kSZ effect unambiguously for the first time, using it to detect the relative motion of galaxy clusters.