Special thanks to:

Robert M. Frostig, science teacher, Horace Mann Junior High School, Charleston, West Virginia.

Michael J. Chovanec, physics teacher; Tobin George, biology teacher; William Fry, science teacher; Hempfield Area High School, Greensburg, Pennsylvania.

Additional thanks to:

Thomas, my husband, for his incredible love and support.

Archie, our Welsh Corgi, for his companionship and friendship.

Shadow, our Russian Blue, for his constant vigil.

Mary, my friend, for love, understanding, and support.

Mom, Dad, Kathy, and Emmett, my family, for so many reasons.

Kate Bradford, my editor, for her expert opinion and advice.

Sam Stier would like to thank his most capable agent, Grace Freedson, for helping create the opportunity to work on this book, and Jean Potter, for putting the wonderful first edition of this book together. The challenge of explaining a wide range of fascinating, complicated physical phenomena to young children has been a wonderful opportunity to try and explain a wide range of fascinating, complicated physical phenomena to myself.