Each individual has a fixed time of birth and fixed time of death. An analogy can be drawn from a simple study of a stone (projectile) thrown into air at a certain speed and direction at a given point of time has a fixed time at which it falls. The direction and projection and the speed will determine the distance (range) at which the stone shall fall.
Incidentally the study also shows that one can uniquely determine its position at any given of time soon after it is projected. This is proven scientifically. This is the basic on which targets are hit and space travel is made possible.
This principle is applicable to each living being and for each event that occurs in the lives of individuals.
Indian philosophers made use of this principle and explained the methods of determining the estimated facts that occur as events in an individual life. One may call it foretelling or astrology or palmistry or by any other name.
They converted the initial velocity and angle of projection as the forces that act on him at the time of birth like that of the projectile. They went further, to the background and said the height at which the projectile is released has an effect on the range and position of the projectile at any given point of time. The height is the mental status a person is born with and the direction of projection is the attitude and the goal which the person was born.
In practical life, the projectile is subject to various forces as it is not projected in vacuum! Thus the method of calculating its position goes through a course correction, and with that, the expectation is proven to be correct. The range would get affected. The external forces and the internal forces determine the trajectory. That shortens the length or lengthens the range. This is true in man’s life’s expectations.