Energía por dondequiera

Who were the earliest Americans? When, how, and from where did they enter and spread across the continent? And what is their relationship to modern Native Americans? Anthropologists develop theories to answer these questions based on the evidence they discover. Their theories—and the discoveries that prove and disprove them—are highlighted in this fascinating volume, full of awe-inspiring facts and incredible breakthroughs. Readers will feel like anthropologists and archaeologists themselves as they read about bones and artifacts, and what they reveal about the ancient cultures that roamed...

Mingling reality and fantasy, the author uses Tato the Duck to help youngsters face their fears and emotions in positive ways and figure out their place in the world

La cultura medieval islámica ha dado figuras espléndidas. Omar Jayyam, poeta y filósofo, algebrista y astrónomo, es sin duda la más fascinante de todas. Su pensamiento fue heterodoxo, su saber inmenso, su obra variadísima. De lo que nos ha llegado de su poesía no siempre es fácil distinguir lo auténtico de lo apócrifo, y de lo que sabemos de su vida, la historia de la leyenda. Su más importante aportación algebraica, la resolución sistemática de las ecuaciones cúbicas cortando cónicas, se procurará poner al alcance de un lector moderno sin alterar las ideas de fondo.

The need for speed is the motivating factor in this engaging, Spanish book. Readers learn the history of travel from the very slow to the supersonic and beyond, including everything in between. They learn and discover the factors that influence motion for all types of vehicles: land, air, and water alike. They also learn different ways to measure speed and read about energy uses for different vehicles. With greater speed comes greater risk. Readers learn how engineers are always seeking new and better ways to keep people safe as they travel faster and go farther. This 6-Pack includes six...