What is time?
is a measurable period during which an action, process, or condition exists
or continues. It is often referred to as the fourth dimension, along with
the three spatial dimensions. Time as a unit is any particular time interval,
used as a standard way of measuring or expressing duration.
is the base unit of time in the SI units that is equal to the duration of
9,192,631,770 periods of the radiation corresponding to the transition
between the two hyperfine levels of the ground state of the caesium-133
is a unit of time conventionally known as
1/24 of a day
Since it varies between seasons, it is made constant by defining it to be
3600 atomic seconds