Gravitation is one of the known fundamental interactions shaping the fabric of the natural world. Although we have been familiar with it since the remote past, our knowledge of it is far less accurate than that of electromagnetism and of the nuclear interactions because of its comparatively feebler intensity. To date, the General Theory of Relativity (GTR) represents the best theoretical description of gravitation at our disposal. As such, GTR is one of the pillars of our knowledge of Nature; intense experimental and observational scrutiny is required not only to gain an ever-increasing confidence about it, but also to explore the borders of the realm of its validity at different regimes ranging from the shortest distances to extragalactic scales.
To this aim, a variety of different theoretical, experimental and observational approaches are required to extend the frontiers of our knowledge of the gravitational phenomena. What are the possibilities opened up by forthcoming space-based missions? What is the status of some long-lasting experimental endeavors aimed to test certain relativistic predictions? Are there some founded hopes to testing newly predicted gravitational effects in the near future in some suitable astronomical and astrophysical laboratories? Might observations collected in the past for various purposes hide some surprises? Do Earth-based laboratory experiments have nothing new to say about gravitation? What is the role of alternative models of the gravitational interaction? These are just some of the questions that the present special issue will try to address.
Prof. Dr. Lorenzo Iorio
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