About this book. Since the publication of Worlds in Collision, Dr. Immanuel Velikovsky's unconventional theories of the origin of the solar system have generated immense interest and bitter controversy. Chief among his critics has been the well-known astronomer, author and television personality, Dr. Carl Sagan, of Cornell University. While brilliantly defending Velikovsky's work, Carl Sagan and Immanuel Velikovsky mercilessly dissects Sagan, his blatantly snide, dishonest and unprofessional '