What are gravitational waves?
They are ripples that carry energy across the universe (ripples in the curvature of space-time continuum). The existence of the gravitational waves was made by Albert Einstein in his general theory of relativity. Till now there was no direct evidence as these waves are hard to be detected.
By BICEP2 (Background Imaging of Cosmic Extragalactic Polarization) - a telescope at South Pole
In proving big bang theory and cosmic inflation.
What is cosmic inflation?
A theory by Alan Ruth that universe expanded very rapidly during its initial formation time.