Newton introduced the concept of
gravitational force to explain the motion of the earth round the sun or that of
the moon around the earth, though his gravitational force was not consistent
with the concept of force as used by his contemporaries. If the western
scientists were consistent they would not have accepted the gravitational force
but that is not the way western science works or how theories (explanations)
are constructed in that system of knowledge. As we have already said it was a
“force” exerted by one body on another without any “physical contact” as such
through a rope, pole or stick. It was not only action at a distance but
instantaneous action. The moment a body (or particle) is “created” anywhere in
the universe it exerted a force (gravitational) on any other body at any other
place in the universe instantaneously. Later on in connection with Quantum
action at a distance Einstein referred to such action as “spooky action at a
distance”.
Almost all the so called educated people
in the world or at least in Sri Lanka believe that there is a gravitational
force as such though they cannot feel it with their sense organs. Gravitational
force (or even gravitational field following Maxwell) is not sensory
perceptible but the “educated people” have no inhibition in believing the
existence of this force “without a rope” though they may not believe in God or
the Natha Deviyo. There are at least a few people who claim to have “seen” the
gods but nobody could claim that he/she has “seen” or “felt” the gravitational
field. Of course one could claim that such seeing is illusion but in the case
of the gravitational force nobody could say it is an illusion either as it is
not to be seen by anybody.
Ernst Mach was against using non
perceptible concepts in western Physics in order to “explain” perceptible
phenomena and he objected to atoms, inertial frames etc., that could not be
seen. Gravitational force also came under the category of concepts and the
existence of gravitation was doubted from the beginning. When somebody says
Newton discovered gravitation it implies that gravitation had been there from
the very beginning and it was left to Newton to discover the force and not
invent, construct or create it. The western scientists are supposed to discover
existing phenomena and not construct.
However, in the
case of gravitation, the question arises as to whether the phenomenon existed
for Newton to discover it. Now let us consider what Newton knew when he
“discovered” the gravitational force. Galileo had observed that near the earth
bodies move towards it with the same constant acceleration. This was only a
speculation though it is now called an observation. The so called experiments
at Pizza in Italy were supposed to be conducted in a vacuum though even today it
is not feasible to create a vacuum in open space. The leaning tower of Pizza
was not in a closed room and it was impossible for Galileo to create a vacuum
surrounding the tower in the seventeenth century. He neglected air resistance
and in order to cover up his work he used objects of similar kind to drop from
the tower and not dissimilar objects such as an apple and a feather. Had
Galileo dropped an apple and a feather from the same height at the same time he
would not have observed the two objects falling to the ground at the same time
and he would not have been able to convince his colleagues that bodies fall
with the same acceleration near the earth. Galileo was better in convincing
others and he was a good marketer.
Newton who was
born a few months after Galileo died was aware of the “experiments” by the
latter and was thinking of a reason to explain the observations of Galileo. Of
course Newton was interested in extra terrestrial activities as well and wanted
to explain the motion of the earth round the sun etc. It was then he had hit on
the idea of a gravitational force which existed universally in the sense that any
two objects (particles) in the universe exerted this force on each other
irrespective of the colour, size, mass etc., of the objects.
However,
Einstein had different ideas and he also did not believe in inertial frames of
reference following Mach. The Newtonian
gravitational force was used in an inertial frame of reference and Einstein was
interested in finding out what happened in other frames of reference. Einstein
who was fond of thought experiments considered a western scientist in a rocket
moving with let us say uniform acceleration in a frame of reference F. Let us
call the frame of reference of the moving rocket frame R. Thus we have two
frames of reference R and F, R moving with uniform acceleration in the frame of
reference F.
Now suppose the
scientist releases some object while the rocket is moving with uniform
acceleration with respect to F. As the object is released it acquires the
velocity of the scientist, and hence of the rocket at the time of release, with
respect to F. However, the object does not acquire the acceleration of the
rocket. This is observed when somebody jumps out of a moving bus, as he
(usually a he and not she) jumps out he has acquired the velocity of the bus
not the acceleration.
In the frame F,
the object begins to move with velocity of the rocket and will continue to move
with the same constant velocity assuming that there are no forces acting on the
object and that F is an inertial frame of reference, and Newton’s laws of
motion are valid.. However, what does the western scientist in the rocket observe?
We assume a pre SMS era and that the scientist does not know that he is moving
in a rocket with uniform acceleration with respect to F. The scientist has no
way of communicating with the external world and he is isolated doing
“experiments”.
As far as the
scientist is concerned he (again he as most of the western Physicists happen to
be males) is at rest in R, which is his frame of reference, but the object he
released though initially instantaneously at rest begins to move with uniform
acceleration in the direction of his feet, in R, assuming of course that he is
not standing on his head, since the object does not acquire the acceleration of
the rocket.
Now the
Physicist, if he happens to be a theoretical person will start thinking why did
the object move towards his feet with uniform acceleration. The observation is
not different from that of Galileo but the latter had not given an explanation
as to why it happened so. It was left to Newton to come out with an answer. Our
friend in the rocket probably thinking like Newton would say the object moved
with uniform acceleration towards his feet in R, as there was a big magnet or
something similar outside the rocket that attracted the object. Now that is a
reasonable explanation though he could have said look we are all moving with
the rocket with the acceleration of the rocket but not the object and hence it
moves in the direction opposite to the motion of the rocket. Who created the
magnet that attracted the object?
Nalin De Silva
08-10-2014