Newtonian Gravity
Yes, gravity has been defined by multiple people, multiple times. One of them, the most famous one, is Sir Isaac Newton. One of the most far-reaching scientific laws ever formulated, Newton’s law of universal gravitation is the basis of celestial mechanics and astrodynamics.
With deceptive simplicity, the law is stated as follows:
“Every particle of matter in the universe attracts every other particle of matter with a force directly proportional to the product of the masses and inversely proportional to the square of distance between them.”
Mathematically, it can be stated as:
\[\begin{equation} \begin{split} F &\propto \frac{m_1 m_2}{r^2} \\ F &= G \frac{m_1 m_2}{r^2} \end{split} \end{equation}\]where:
- \(m_1\) and \(m_2\) are the masses of the two particles / bodies
- \(r\) is the distance between them
- \(G\) is the universal constant of gravitation
The universal constant of gravitation, \(G\), is a constant of proportionality that is dependent on the units used to measure mass and distance. It is a very small number, and is usually expressed in scientific notation as:
\[\begin{equation} G = 6.674 \times 10^{-11} \frac{m^3}{kg \cdot s^2} \end{equation}\]The force of gravity is a vector quantity, and is directed along the line joining the two bodies. The force is attractive, i.e. it is directed towards the other body.