The Second Messenger

We have explored the universe with light and other electromagnetic waves from the beginning of civilisation. All the waves that we have detected from the outer space were electromagnetic waves, be it the visible light, radio waves, X-rays, gamma rays, or microwave. Since 2015, we have started detecting another type of wave which was predicted by Albert Einstein way back in 1916,Gravitational waveWavegravitational so the discovery came almost a century later. This is called the gravitational wave. We have just begun a new era in astronomy, looking at the universe with a new type of wave. This chapter will be on the theory and detection of those waves.