Gravity – The mysterious force!
It is a very common observation that when we toss something in air, it falls
back to earth surface. Why? The answer lies in a very simple word “Gravity”!
...Today in the world of Physics, four natural forces are considered as
fundamental forces; namely Electromagnetic Force, Strong Nuclear Force, Weak
Nuclear Force and Gravitational Force. Amongst all these forces, the
Gravitational Force is the weakest force having largest value of effective
range; while the Strong Nuclear Force is the strongest force having smallest
value of its range, which is confined within the Nucleus of an atom only.
The gravitational force is a very mysterious force as it possesses very strange
properties. It is the weakest force of the universe, but its effective range is
infinite! It means that no matter how great the distance between an object and
the Earth, the Earth’s gravitational force does not drop to zero. The
gravitational influence of every object is exerted through all space. It is
always attractive in nature but never shows repulsion in any condition. It is
effective for smaller bodies of atomic or molecular sizes, and also holds
together the massive bodies such as galaxies, stars, planets, satellites etc.
Gravitational Force is a natural force which plays the most significant role in
this universe. Today we all know that the motion of all the heavenly bodies
including stars, planets and satellites is significantly affected by the
gravitational force. But the knowledge of this mysterious natural force has a
history of just about 300 years approximately only.
Initially the Greeks believed that this earth is the centre of whole universe
and all the heavenly bodies like sun, moon, and all stars revolves around the
earth in circular orbits. Greek philosophers thought that the planets and stars
were part of the god’s realm and followed a ‘Natural Motion”. They did not
realize that some natural force like Gravity is involved. The Greeks’ ideas
struck around until the 16th century.
But the concept of centre of universe was challenged by some experimental
scientists like Galileo and Tyco Brahe, when they observe the sky by Telescope.
And then the concept that ‘Sun is the centre of this whole Universe’ was
developed. Beginning in the 1500s, though, astronomers like Galileo and Tyco
Brahe discovered that the earth and the other planets revolved around the sun in
circular orbits, Johannes Kepler showed that they moved in an elliptical orbit.
But Kepler was not able to explain why their orbits were elliptical and not
circular in shape, because up to that time, they were unaware of the concept the
‘Gravitational Force’.
The first correct explanation about all these celestial motions came when Sir
Isaac Newton discovered Gravity. It is believed that Sir Isaac Newton
(1642-1727), an English mathematician and physicist discovered the basic concept
of ‘Gravity’ when he saw a falling apple while thinking about the forces of
nature. Whatever really happened, Newton realized that some force must be acting
on falling objects like apples because otherwise they would not start moving
from rest.
Newton extended his concept of Gravity from a falling apple to the moon which is
revolving around the earth; and then beyond that into the extremities of this
universe. The moon is only a projectile which circulates around the earth under
the gravitational attraction. Newton realized that the moon would fly off away
from the earth in a straight line tangent to its orbit, if some force was not
causing it to fall towards the earth, and that force was ‘Gravitational Force’.
Newton termed this natural force as ‘Gravity’. He also discovered that this
gravitational attraction is present between each and every massive object
present in this universe, irrespective of its shape, size and mass. The work of
Galileo, Brahe, Kepler and Newton proved once and for all that the Earth wasn’t
the centre of the solar system. The earth, along with all other planets orbits
around the sun.
Albert Einstein developed a new idea about Gravity. According to him, Gravity
arises from the warping of space and time. In Einstein's theory of special
relativity, inertial mass is a manifestation of all the forms of energy in a
body, according to his fundamental relationship E = mc2, E being the total
energy content of a body, m the inertial mass of the body, and c the speed of
light.
The concept of Gravity is yet not solved or understood completely. The journey
of human knowledge about this universe and its creator is at present in a very
fast speed track. The fall of an apple ignited the human mind to explore this
universe, now it will goes on and on till we come to know the ultimate reality
of this universe.