Walker, Sally M

Explains the concepts of work, gravity, and friction, describes machines and inclined planes, and includes simple experiments.

Describes the formation and movement of different types of glaciers and their effects on the land. Includes resources and a glossary.

Text and pictures describe the Earth's caves, including their different types, animal life, and how people explore them.

Describes work and simple machines in everyday surroundings, and presents experiments that explain how machines make work easier.

Describes work, machines, inclined planes, gravity and friction, and wedges in everyday surroundings, and presents experiments that explain how they work.

Describes work, machines, gravity, friction, and pulleys in everyday surroundings, and presents experiments that explain how they work.

Offers a look at the history of climate change, how it will unfold over the next century, and what we can do to prevent a cataclysmic future.

Opossum and her babies encounter danger as they search for food at night.

Tells the story of the discovery of a strange fish in South Africa in 1938 which was identified as a coelacanth fish believed to have become extinct along with the dinosaurs, and discusses subsequent efforts to learn about the coelacanth and the mysteries that remain unsolved.

Eight-year-old Letty attempts to save her pet goose from marauding British soldiers in New Jersey during the Revolutionary War.