For a long time, what we now know as "space" was inaccessible and off-limits to humans, not because it was at a height which was unattainable without the least astronautical technology or principles, but because of the cosmic and dualistic representation of reality. Reality was seen as a nice, orderly whole, which the Greeks specifically named "cosmos", within which humans were relegated to the centre – to a sort of "cesspit" of imperfection, alteration, incompleteness and finally death. Around them were crystal spheres which held the planets and stars – immutable, eternal and perfect – a domain which was completely off-limits to humans, unless they had discarded their carnal envelope, either through a mystical experience or after death. It took a revolution, what we now call the Copernican Revolution, to shatter the celestial spheres and make them no longer forbidden territory. Galileo was one of the first revolutionaries: through his astronomical observations, he showed that the Earth and the Sky were in fact made of the same fabric, the same material, and therefore belonged to the same world. He argued for the unification and equalization of the universe, its content and its laws. Johannes Kepler, having read Galileo's observations and findings in a work entitled Starry Messenger which Galileo had sent him in April 1610, decided to give the latter his full-fledged support, and penned his Conversation with the Starry Messenger in just eleven days. He wrote: There will certainly be no lack of human pioneers when we have mastered the art of flight. Who would have guessed that navigation across the vast ocean is less dangerous and quieter than in the narrow, threatening gulfs of the Adriatic, or the Baltic, or the British straits? Let us create vessels and sails appropriate for the heavenly ether, and there will be plenty of people unafraid of the empty wastes. In the meantime, we shall prepare, for the brave sky-travellers, maps of the celestial bodies - I shall do it for the Moon and you, Galileo, for Jupiter[i]. Intoxicated with the idea that mankind could one day escape its terrestrial prison, the little dungeon described by Pascal, Kepler was convinced that now nothing was too high or too far for humanity to set its sights on reaching it. Rather than concerning himself with how to construct these vessels of the sky, Kepler left the task of inventing the art of flying to his engineers, and devoted himself to producing the maps which would be used by the first sky travellers. He saw the astronomer's work of map-making as essential, in order to distinguish and discover the worlds and islands, the reefs and sandbars that the conquistadors of space would encounter in their travels. Thus, the work of astrologists and soothsayers came to an end: it was no longer a question of reading the sky for fates and fortunes, or worse, the punishment awaiting intruders into the domain of some celestial power; it was a matter of assisting those who would one day attempt to write the destiny of humanity in the sky – the future explorers of space. Centuries passed, and humans conquered air, and then space. Their feet touched the surface of the Moon and their wheels touched the surface of Mars. They acquired the vision of the gods; they peered into an abyss almost 13 billion light-years deep. The Earth and, with it, the entire universe somehow became flat again with no folds, no curves, at least in appearance, to hide any dark corners. The horizon once again retreated out of reach taking with it perhaps the last dreams of exploration. Not so. 21st century humans experienced the same strange feeling of suffocation described by Pierre Loti in his Roman d'un Spahi written in 1881 describing a young mountain dweller who, sent to Senegal by the French government as a soldier, discovered the desert: yet the endless level always ended by saddening him and weighing on his imagination, accustomed to the hills; he felt a craving to go on and on, farther and farther, as though to widen his horizon, to see what was beyond. Loti is right: the human imagination does not like horizons which are too flat, too clear ; humanity needs to meet resistance, brakes, contraints to better brake them, to cross them and to lead humans to new terrae incognitae, to new unknown territories. Does our actual experience of reality, from the subatomic to the astronomical scales, possess sufficient reliefs to which our imagination can encounter or is it on the contrary too flat to stimulate it? Is it possible that the powerful spring of exploration could miss one day to humanity?