Science is at the heart of real science fiction, which is more than just westerns with ray guns or fantasy with spaceships. The people who do science and love science best are scientists. Scientists like Isaac Asimov, Arthur C. Clarke, and Fred Hoyle wrote some of the legendary tales of golden age science fiction. Today there is a new generation of scientists writing science fiction informed with the expertise of their fields, from astrophysics to computer science, biochemistry to rocket science, quantum physics to genetics, speculating about what is possible in our universe. Here lies the sense of wonder only science can deliver. All the stories in this volume are supplemented by afterwords commenting on the science underlying each story.