John pritchett (359 resultados)

Condición: Good. : Una señal proveniente del espacio profundo desata un ajuste de cuentas global cuando la Dra. Nova Jamil detecta una transmisión misteriosa. Mientras los gobiernos luchan por el control y el miedo amenaza con iniciar un conflicto, una pequeña tripulación es enviada a interceptar la fuente en un viaje que pondrá a prueba los límites de la confianza, el valor y el descubrimiento.El comandante Isaac Blake y la teniente Juno Trent se aventuran más allá de la cara oculta de la Luna, descubriendo un artefacto alienígena que ofrece más que respuestas: ofrece una elección que podría unir a la humanidad o destruirla. Esta es una apasionante novela de ciencia ficción dura sobre el momento en que la humanidad da un paso más allá del miedo hacia lo desconocido. EAN: 9798231427246 Tipo: Libros Categoría: Ciencia Ficción|Literatura y Ficción Título: The Signal: Journey Beyond the Stars Autor: John Pritchett Editorial: John Pritchett Idioma: en Páginas: 106 Formato: tapa blanda.…

Paperback. Condición: new. Paperback. More than a billion years ago, Earth had land, oceans, atmosphere, energy, and life-but the planet still did not fully work as a living system.Rodinia: The Mother of Supercontinents explores a vanished world in which the essential ingredients for habitability were present but poorly coordinated. The land was barren and exposed. Oxygen existed, but it was low and unstable. Ozone formed, but protection from ultraviolet radiation did not hold consistently. Water supported life in the oceans, yet the continents lacked mature soils, rooted vegetation, and dependable systems for retaining moisture and nutrients.John S. Pritchett presents Rodinia not simply as an ancient arrangement of joined landmasses, but as a crucial stage in the development of Earth itself.Rodinia was a planet that almost worked.Its immense interior lay far from the moderating influence of the oceans. Rain fell on bare rock and quickly ran away. Nutrients were released but not held in place. Temperature extremes intensified inland, while climate feedbacks could push the planet toward severe cooling and later warming.Life persisted, but mostly within water.The oceans reduced radiation, moderated temperature, circulated nutrients, and provided the continuity the land could not. Microbial communities survived in shallow marine environments where sunlight, chemistry, and protection came together. Along tidal margins, repeated cycles of submersion and exposure created changing conditions in which new biological possibilities could emerge.The problem was not the absence of life. It was that life could not yet scale.The book examines: Unstable oxygen and uneven ozone protectionA surface exposed to ultraviolet radiationVast dry interiors far from ocean moistureThe absence of mature soil systemsPoor retention of water and nutrients on landClimate feedbacks capable of driving extreme cooling and warmingA hotter, more tectonically active EarthOceans that protected life while also confining itRodinia's importance becomes clearest when the supercontinent begins to break apart. Rifting opens new ocean basins. Coastlines multiply. Shallow marine environments expand. Ocean circulation changes. Moisture reaches more regions, and exchanges among land, water, atmosphere, minerals, and life become more active.The breakup does not suddenly create the modern Earth. It does something more fundamental: it begins loosening several constraints at once.Rodinia's assembly concentrated the problem. Its breakup changed the conditions under which the problem could eventually be solved.As biological activity became more sustained in expanding marine environments, oxygen production could become more reliable. More consistent oxygen supported stronger ozone formation. Better protection reduced surface radiation. New coastlines created additional zones where sunlight, nutrients, water, and life could interact.Accessible, richly illustrated, and grounded in geology, climate science, oceanography, atmospheric chemistry, and the history of life, Rodinia: The Mother of Supercontinents reveals why habitability depends on more than the presence of the right ingredients.It depends on whether planetary systems reinforce one another-and whether favorable conditions persist long enough for complexity to build.Rodinia was not the first world or the final world. It was the world in which the difference between having the pieces and having a functioning system began to emerge. Before the modern world stabiliz Shipping may be from multiple locations in the US or from the UK, depending on stock availability.…

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