Agujeros negros (Black Holes)

For many years, people believed there were nine planets that orbited the sun. Now we say there are eight. What happened to the ninth planet, Pluto? What are the different planets like? What exactly makes a planet a planet? These are the many intriguing questions answered with this high-interest book, crafted to be accessible for readers of all levels. Young astronomers will be especially fascinated by the stunning photographs and the "Make the Grade" fact boxes.

La industria aeroespacial es la segunda actividad más normada luego de las activi- dades nucleares; está regida por infinidad de normas, reglamentaciones, directivas, documentación específica y todo tipo de manuales de referencia obligatoria. La gran mayoría llega a manos de usuarios, operadores, talleristas, etc. en idioma in- glés, el idioma de uso aeronáutico por naturaleza. A ello se suma el hecho de que la industria aeronáutica no está aislada de las actividades humanas, sino que inte- ractúa, se nutre y hace su aporte a ellas creando la necesidad de un sólido...

Thomas Edison is considered by many to be one of the greatest inventors of all time. His creations changed the world, but there was more to his life than just his inventions. Readers of this engaging volume will learn all about the man behind the innovations. This fascinating biography introduces important subjects and encourages a further interest in history. Concise and accessible text paired with vibrant photographs is sure to captivate audiences of many ages and levels.

Las vidas del Dr. Bethune complementa otras muchas investigaciones previas llevadas a cabo tanto por los Stewart como, en el caso español, por Jesús Majada, comisario de la exposición La carretera Málaga-Almería, visitada por casi cinco mil personas en la Universidad de Salamanca en octubre de 2006. En palabras del profesor Rodríguez Celada, director de la colección editorial “Armas y Letras” y autor del prólogo, nadie podía permanecer indiferente ante “el genio extemporáneo, el líder indiscutible, el adalid temerario, el jefe autoritario, el paladín romántico, un ser...

It is the third Monday in January and school is closed. But do you know why? It's Martin Luther King Jr. Day. Turn the pages of this book to find out what dream Dr. King shared with the world, who Mohandas Gandhi was, how one brave woman helped Martin Luther King Jr. change history. Each book in the Holiday Histories series describes one of America's holidays or special days. Explore the history of each day and learn the real reason why it is important. Discover what special meaning each day might have for you.