A French Scientist, Coulomb (In 1875): First experimentally measured the force of attraction (or repulsion) between two charges. On the basis of his measurements, Coulomb enunciated a law, called Coulomb's Law.
"Two charges attract (or repel) each other with the force, which is directly proportional to the product of the magnitude of the charge and inversely proportional to the square of the distance between them."
The force is along the straight line joining them, as shown in figure below. This law is based on the inverse square law.
Let $Q_1$ and $Q_2$ be the two charges, separated by a distance $(r)$ then,
Mathematically,
$F = k.\frac{Q_1 Q_2}{r^2}$ .......... (i)
Where, $k$ is the constant of proportionality. It's value depends upon the medium between the charges. If the charges are situated in vacuum (or air) in SI Unit,
$F = \frac{1}{4 \pi \epsilon_0} \frac{Q_1 Q_2}{r^2}$ .......... (ii)
Where, $\epsilon_0$ = permittivity of free space (or vacuum) = $8.854 * 10^{-12} \frac{C^2}{N\;m^2}$.
If the two charges have the same sign, the electrostatic force between them is repulsive. If they have different signs, the electrostatic force between them is attractive.
The Natural force that tends to cause physical things to move towards each other.
First, [Newton's Law of Universal Gravitation] is a mathematical in its expression.... Second, it is not exact. Einstein had to modify it.... There is always an edge of mystery, always a place where we have some fiddling around to do yet.... But the most impressive fact is that gravity is simple.... It is simple, and therefore it is beautiful.... Finally, comes the universality of the gravitational law and the fact that it extends over such enormous distances....
~ Richard P. Feynman.
Sir Issac Newton:Albert Einstein:
$F = G\frac{m_1 m_2}{r^2}$
$G\mu \nu = 8\pi GT\mu \nu$
» It is a force.
» It is a distortion of space and time.
» It depends on mass and distance.
» It depends on Energy.
» Newton's stated that the force of gravity is always attractive. It affects everything with mass, work instantaneously at a distance and has an infinite range. "Every mass attracts every other mass in the universe (across the empty space)", Newton had imagined. [1]
» But in Einstein's model, gravity is not a force. It is a warping of space-time. Space is really curved, and as a result objects are deflected from a straight path in a way that looks like a force. According to Einstein: "Mass tells space how to bend, and space tells mass how to move".
