Basics of Astronomy: The Four Forces of The Universe

There are four fundamental forces in the universe, all other forces are derivatives of these. These are Gravity, Electromagnetism, Weak Force, and Strong Force.

Gravity is the weakest force, but it has an infinite range. Every object in the universe exerts a gravitational force on every other object in the universe, no matter how far away. But it is weaker than other forces even though it holds galaxies and stars together. And it has almost no effects at atomic and molecular levels.

Weak Force or Weak Nuclear Force causes particle decay, one subatomic particle changes to another. It also powers the nuclear fusion of stars and produces the energy we require. It is the weakest fundamental force other than gravity.

Electromagnetic Force or Lorentz Force has electric and magnetic forces. This is basically electron attracting proton. Like charges repel, unlike charges attract. And this one too is infinite. An electron placed on Mercury does attract a proton placed on Neptune, but the force is very very small.

Strong Force or Strong Nuclear Force is the strongest fundamental force, it is six thousand trillion trillion trillion times stronger than gravity. It holds together the sub-sub atomic particles, the quarks that form protons and neutrons. It holds even the proton and neutrons together in an atom. The protons are all positive, so they should repel each other, but it is the strong force that keeps them together.