Cuando la gravedad es lo bastante elevada no deja escapar nada, ni siquiera la luz. Un lugar así recibe el nombre de agujero negro. Es una especie de… - Carl Sagan

For the price of a modest meal you can ponder the decline and fall of the Roman Empire, the origin of species, the interpretation of dreams, the nature of things. Books are like seeds. They can lie dormant for centuries and then flower in the most unpromising soil.

... [W]hat is the likelihood that only on ordinary star, the Sun, is accompanied by an inhabited planet? Why should we, tucked away in some forgotten corner of the Cosmos, be so fortunate? To me, it seems far more likely that the universe is brimming over with life. But we humans do not yet know. We are just beginning our explorations. From eight billion light-years away we are hard pressed to find even the cluster in which our Milky Way Galaxy is embedded, much less the Sun or the Earth. The only planet we are sure is inhabited is a tiny speck of rock and metal, shining feebly by reflected sunlight, and at this distance utterly lost.

In the spring of 1974 about two years before the Viking spacecraft landed on Mars, I was at a meeting in England sponsored by the Royal Society of London to explore the question of how to search for extraterrestrial life. During a coffee break, I noticed that a much larger meeting was being held in an adjacent hall, which out of curiosity I entered. I soon realized that I was witnessing one of the most ancient scholarly organizations on the planet. In the front row a young man in a wheelchair was, very slowly, signing his name in a book that bore on its earliest pages the signature of Isaac Newton. When at last he finished, there was a stirring ovation. Steven Hawking was a legend even then