 The 2021 Dirac Medal celebrates theoretical work about gravitational waves. Gravitational waves are a very very hot topic nowadays in physics. These waves are produced by what are called binary systems. It is to say two stars or two black holes which are orbiting each other and radiating these gravitational waves. Gravitational waves are the analogue of electromagnetic waves but for gravity and they are very very feeble, they are very very difficult to detect and they were detected for the first time in 2015 after many decades of work. Now in order to detect this very very tiny signal you really need to know what you are looking for. You need to know what kind of wave comes to your experimental detector and this is the place where the work of the medalist enters so they were able using different techniques to calculate starting from general relativity which is the theory of gravity from Einstein. They were able to calculate the wave which is produced by these binary events depending on for instance the mass of two objects, how they rotate and so on and so forth. So the Dirac Medal celebrates theoretical physics but this time is very close to experiment because this work was really instrumental in order to be able to detect finally these gravitational waves and it's also a work that would be very important in the future. In the future there are new experiments coming along with more and more precision and in order to, since you have a better experimental accuracy you also need to do better and better calculations on the theory side and the techniques pioneered by these four people will be crucial also in the future.