What is Weak Force? Can somebody please tell me?

http://en.wikipedia.org/wiki/Weak_interaction

remember wikipedia is always a good place to begin when you want to learn about something new online ... it's only a start though and for science topics, to understand properly, you need to red books by proper experts .... but hey, for now, keep exploring the link, go read other links below the article if you want.

Weak interaction (often called the weak force or sometimes the weak nuclear force), is one of the four fundamental forces of nature, alongside the strong nuclear force, electromagnetism, and gravity. It is responsible for the radioactive decay of subatomic particles and initiates the process known as hydrogen fusion in stars. Weak interactions affect all known fermions; that is, particles whose spin (a property of all particles) is a half-integer.

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Weak nuclear forces are responsible for radioactivity and also for exhibiting some peculiar symmetry features not seen with the other forces. In contrast to electromagnetic and strong forces, the strength of the weak force is different for particles and anti-particles (Charge Violation), for a scattering process and its mirror image (Parity Violation), and for a scattering process and the time reversal of that scattering process (Time Violation).

The weak force drives radioactive decays that:

help generate sunlight,

enable advanced medical diagnosis and treatment,

help determine the age of organic materials from carbon isotope abundances,

help determine the age of the earth from uranium isotope abundances

provide heating for the Earth and an energy source for plate tectonics, through the decays of Uranium, Thorium and Potassium.