The explanation spoken of here is popularly termed 'the ele-vator analogy' (Refer p. 49, Illustration A.) : "An elevator car is depicted as falling down the shaft of a very high building after having parted its restraining cables. A group of human passengers perform experiments. They hold out objects and release their grip on them - the objects (cannonballs, bb-shots, pound of butter, wristwatch, etc.) remain suspended in midair; they do not accelerate downward. Because, all of the released objects are falling within and along-with the elevator and its passengers at 32 ft. per-second-per-second (16 ft per second, squared); in accordance with Newton's laws of gravitation (on or of, earth). "The observers in the elevator are unaware of their predicament. They understand and explain the suspension of objects and them-selves in mid-air, by assuming they are outside the gravitational influence of the earth, and logically conclude that they are 'free-floating' in space where there is no significantly measurable force of gravity at all (‘a macrocosmic ‘weak force’ - the opposite of microcosmic ‘strong nuclear binding force’. They are generally misperceived as be-ing unrelated; ‘two different kinds of forces’. The record proves they are qualitatively the same force, quantitatively occurring in two different - large and small/ tenuously thin and densely com-pacted - places/coordinate systems). "It is an apparently sensible conclusion, that they are in a coordinate system which is free-floating in deep space. In leaping from the floor, they float smoothly toward the ceiling with a velocity directly proportional to the vigor of their individual leaps. If/when they push a suspended/floating object in any direction, that object continues to move in a straight line with uniform velocity, until it strikes the wall of the elevator car. Galileo's and Newton's Laws Of Inertia prevail exclusive of gravity and are obeyed. "Newton's Laws of Gravity are pointless to consider in the elevator at this time. Because there are no significantly measurable gravitational effects in it, to influence its passengers and their experiments. The environment of the interior elevator is therefore purely and exclusively an inertial system, desti-tute of gravity and gravitational effects. THERE IS NO WAY FOR THE OB-SERVERS INSIDE THE ELEVATOR TO DETERMINE WHETHER THEY ARE FALLING IN A GRAVITATIONAL FIELD (as they actually are), OR SIMPLY 'FREE-FLOATING' IN THE VOID OF DEEP SPACE, FREE OF ANY GRAVITATIONAL INFLUENCE WHATSOEVER. "Then Einstein alters the situation of the elevator and its passen-gers. (Refer p. 49, Illustration B) "This time the experimenting passengers are still in the elevator, but they actually are in the void of deep space, far away from any appreciable gravitational influence. "A cable is attached to the roof of the elevator car and an arbitrary force winches-in the cable at 32 feet per-second squared. The elevator is therefore accelerating 'upward' through space (any direction in which the elevator car happens to be pulled by the cable is 'upward' relative to the passengers within it). Again, the observers within the elevator have no idea where they are, and again they evaluate their situation by performing experiments. Their feet now rest firmly on the floor; they now have their 'normal' (as experienced on earth) body weight to support. Confirmed by scaled weight measurement. (The observers are actually measuring and obtaining inert mass values; not realizing they are not measuring gravitational mass values: their coordinate system having found the two values identical under the accelerating circum-stances; indistinguishable from each other. Inertial & Gravitational Mass Values; which are not supposed to have anything to do with each other, are ‘likewise indistinguishable’ at this *juncture. Which Einstein called *‘aston-ishing’. The *‘coincidental’ confluence of two different methods of measuring and defining mass value; arriving at exactly the same - ‘unrelated’ coordin-ates. *A pound of butter offers exactly a pound of resistance to acceleration exactly equalling the descent rate of objects in free-fall on earth.: 32’ per" 2. "When they jump, they do not float to the ceiling because the floor is constantly accelerating upward beneath them at the descent-rate for free-falling objects on earth. When the observers and various objects are weighed on a standard scale within the elevator at this time, they all have their 'normal' earth-weight (heavy mass value ). Due to their resistance - generated by body-mass's - negative inertia: the tendency of all bodies at rest to remain at rest and offer resis-tance to outside forces acting upon them, including non-uniform motion That is to say: '‘ inert mass value’ , opposing the acceleration (non-uniform motion) of the elevator floor. If the elevator were accelerating at less than 32 ft. per-second, the objects and observers would weigh correspondingly less than their normal earth weight. If the elevator were accelerating at more than 32 ft. per-second, the objects and observers would weigh correspondingly more than their normal earth weight. When the observers in the test elevator release objects from their grip, the objects appear to descend vertically/'fall'/accelerate-'down-ward' @ 32 ft. per-second (per second). When objects are tossed or pushed in a horizontal direction, those objects do not move in a straight line in accordance with the laws of inertia; instead the paths of the tossed objects - due to the acceleration of the elevator car - describe a parabolic curve; descending vertically at 32 feet per sec-ond squared, relative to the floor; in accordance with the laws of gravitation. "The observers remain unaware that their room is accelerating (ascending ever-faster) through deep space. They understandably conclude from direct experience and experimentation, that they are situated in quite ordinary circumstances in a windowless room on earth, influenced by conventional gravity. THERE IS NO WAY FOR THE OBSERVERS TO DETERMINE FROM WITHIN THE ELEVATOR (coordinate system) WHETHER THEY ARE AT REST IN THE EARTH'S GRAVITATIONAL FIELD; WHERE ALL OBJECTS ARE 'PULLED' DOWNWARD @ 32 ft. per-second BY GRAVITY, or: WHETHER THEY ARE ACCELERATING IN AN INERTIAL SYSTEM (which they are in this case, @ 32 ft. per-second squared): WHERE THERE IS NO GRA-VITY WHATSOEVER. "From his imaginative and now renowned 'elevator analogy', Ein-stein formulated a conclusion of unprecedented theoretical import-ance; that being: The General Principle Of Relativity: THERE IS NO WAY TO DISTINGUISH THE MOTION PRODUCED BY INERTIAL FORCES (acceleration/centrifugal and centripetal force), FROM MOTION PRODUCED BY GRAVITATIONAL FORCE. "This is the General Principle Of Relativity. Fact #2. It borders on being a statement of the obvious, but we are about to see that sometimes it isn’t so obvious at all. That people in general everywhere, actively refuse to recognize it, altogether.