Positivity in the Sky

Throughout our history, we have gathered information from the Universe that surrounds us through the light it emits. We have seen the Universe through our own eyes and instruments. The direct detection of gravitational waves in 2015 has marked the beginning of a new era for science where we are now able to "hear" the Universe through a new channel, with an opportunity to probe gravity at its most fundamental level. But how much do we actually know about gravity and how gravitational waves propagate? I will discuss the subtle interplay between the behaviour of gravity as we observe it in our “everyday experiments”, and its embedding within an ultimate high energy completion.