Exploring the Universe with Gravitational Waves
With the recent detections of GW150914 and GW151226 we have entered the era where we can begin to use gravitational waves (GWs) to explore the Universe. We will give a short overview of two mechanisms of GW production that can give information unaccessible by electromagnetic observations. Namely, we will discuss GW emission by quasi-normal modes of black holes, as well as stochastic GW backgrounds produced in the early Universe.