The Manhattan Project was a research and development during World War II that produced the first nuclear weapons. From 1942 to 1946, the project was under the direction of Major General Leslie Groves. Nuclear physicist Robert Oppenheimer was the director of the Los Alamos Laboratory that designed the actual bombs. The Army component of the project was designated the Manhattan District as its first headquarters were in Manhattan. The Manhattan Project employed more than 130, 000 people and cost nearly $2 billion ($24 billion in 2021. Research and production took place at more than thirty sites across the United States, the United Kingdom, and Canada. The atomic bomb test in New Mexico on Monday July 16, 1945 produced heat hotter than the sun. This book "Day Of the Double Sun - The Manhattan Project" traces the development and test of the world's first atomic bomb.