The universe stretches across billions of light years, and we know so little about it. Could this mean that there are other intelligent beings out there? Some people believe there are--and that those intelligent beings can sometimes be seen from Earth traveling by UFOs! This volume avoids the sensationalism often attached to debates about UFOs and aliens. Instead, scientific facts are coupled with historical information and firsthand accounts to teach students about responsible research, evaluation of sources, and critical thinking, even when confronted with the unknown.