billy_joule said:Are you talking about the gravitational constant? 'G'?
http://en.wikipedia.org/wiki/Gravitational_constant
Newton never found it's value, It's measurement is generally attributed to Cavendish:
http://en.wikipedia.org/wiki/Cavendish_experiment
The gravitational force of an object is the force of attraction between two objects that have mass. It is the force that keeps objects with mass, such as planets, moons, and stars, in orbit around each other.
The gravitational force of an object is calculated using Newton's Law of Universal Gravitation, which states that the force between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
The gravitational force of an object is affected by two main factors: the masses of the objects and the distance between them. The greater the mass of the objects, the greater the force of attraction between them. The farther apart the objects are, the weaker the force of attraction between them.
The gravitational force of an object varies on different planets due to differences in their masses and sizes. The larger the planet's mass, the stronger the gravitational force. The closer an object is to the planet's center of mass, the stronger the gravitational force will be.
No, the gravitational force of an object cannot be negative. The force of gravity is always attractive, meaning it pulls objects towards each other. It can only have a positive value.