# Space, time, and mass in physics

## 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.

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