The force of which we are constantly aware in our daily lives is that which pulls us towards the earth. This is called gravitational force. Sir Isaac Newton came to the conclusion that gravitational force exists between all bodies. Thus, two stones are not only attracted towards the earth but also attract each other. Normally, we do not notice this force owing to its smallness, although it can be measured with sensitive instruments. Nevertheless, two 50000 t ships lying side by side attract each other v it a force of about 180 Newton ‘s law of universal gravitation states that any two particles of matter attract one another with a force which is proportional to the product of their masses and inversely proportional to the square of their distance apart. Strictly, this law apple only when the distance is large compared with the dimensions of the articles.
newton realized that gravitational attraction applied not only to bodies on the earth but was also responsible for holding the moon in its orbit about the earth and also the earth and its fellow planets in their orbits round the sun.