Question

why G is called universal constant ​

Answer 1

The value of G does not depend on the nature of the intervening medium. Also, G is constant for any object in the universe. Hence, is is known as 'universal gravitational constant'. Gravitational force acts on all objects in proportion to their masses.

Answer 2

Good is called universal constant because it's value is fixed throughout the universe which is 6.67 x 10-¹¹m3/kg s2