Space, time, and mass in physics
Classical mechanics is known as Newtonian mechanics. In this mechanics concept
of three fundamental quantities has been considered. These are space, time,
and mass.
Space: According to Newton, space is an absolute quantity that exists
in itself. It is not related to any outer or external thing and is not
influenced by the environment. For example, the length of a body does not
depend on the motion of the body or observer and is unchanged at rest.
Time: According to Newton time is naturally an absolute quantity and
does not depend on any other outside object and proceeds uniformly. So, time
is universal and it moves at a fixed rate that does not depend on the object
or observer. From this we can conclude two things :
1) Whether an observer is at rest or in motion, the time interval between any
two events is the same for all observers and
2) Two events occurring simultaneously to an observer, time will be the same
to the observer no matter what the state of motion is.
Mass: In Newton’s mechanics, the mass of a body is a fundamental
quantity that is not dependent on its motion and according to the conservation
principle of masses, masses of bodies of independent processes, do not change
due to action-reaction between two or more bodies within those process.
The modern concept of Space, Time, and Mass in Physics
Scientist Einstein proved that the fundamental quantities of classical
mechanics change with motion. So the above three quantities are not
fundamental.
Space: The length of a body in motion contracts and becomes less
than the length at rest which is called length contraction. So, the length of
a body contracts with motion.
Time: The time span of an event in a static reference will be
larger in a frame of reference in motion. This phenomenon is called time
dilation. So, with motion time dilation takes place.
Mass: If a body is in motion its mass increases. This event is called
the relativity of mass or increase of mass due to motion.
