The Four Forces

Gravity, Electromagnetism, The Strong Effect, The Weak Effect

The four fundamental forces of nature form.  Those forces underpin everything around us.   (Gravity, Electromagnetism, The Strong nuclear force, The weak nuclear force.)

The weak force is about a billion times less strong than electromagnetism.  It's responsible for radioactivity. 

In consequence, the old psychology was thoroughly unseated and as much revolutionized as classical physics had been by the discovery of radioactivity. 

Electromagnetism is carried by photons.  The strong force is carried by particles called gluons.  The weak force by particles called the W & Z bozons.  But they never found the force carriers for gravity - the elusive gravitons.  And that's where "their" efforts to unify the math of the universe are stuck. 

http://science.discovery.com/videos/master-of-the-universe-stephen-hawking-4-forces.html    (link)

Math:  http://hyperphysics.phy-astr.gsu.edu/hbase/forces/funfor.html

Electromagnetism explained the relation between electricity and magnetism, but then went on to explain the nature of light, radiowaves, x-rays.