Dark Energy

Abstract: Among the great mysteries that physics has not yet solved are undoubtedly those of dark energy and dark matter. In this chapter we deal with the first of them. We will expound in detail the motivations that led to hypothesise the existence of dark energy, the importance of understanding its nature, its main possible theoretical explanations and a list of the many attempts at modelling it. We conclude with a description of the most recent and future missions on Earth and in space devised to shed light on this mystery.