Book excerpt: Astronomy isthemostancientsciencehumanshavepracticedonEarth. Itisascienceofextremesandoflargenumbers:extremesoftime–fromthe big bang to in?nity –, of distances, of temperatures, of density and masses, ofmagnetic?eld,etc.Itisasciencewhichishighlyvisible,notonlybecause stars and planets are accessible in the sky to the multitude, but also - cause the telescopes themselves are easily distinguishable, usually on top of scenic mountains, and also because their cost usually represent a subst- tialproportionofthenation’sbudgetandofthetaxpayerscontributionsto that budget. As such, astronomy cannot pass unnoticed. It touches on the origins of matter, of the Universe where we live, on life and on our destiny. It touches on philosophy as well as on religion. Astronomy is the direct c- tactofhumankindwithitsoriginsandtheimmensityofuniversalnature.It is indeed a science of observation where experimentation is practically - possible and which is ruled by mathematics, physics, chemistry, statistical analysis and modelling, while o?ering the largest number of veri?cations of the most advanced theories of fundamental physics such as general r- st ativity and gravitation. At the beginning of the 21 century astronomy is clearly a multidisciplinary activity touching on all aspects of science. It is therefore logical that in the past and still now, astronomy has attracted the most famous scientists, be they pure observers, mathematicians, physicists, biologists, experimentalists, and even politicians.