The Bomb that Changed the World By Armando, Monica, Sanne, Taylor, Ben www.dailymail.co.uk

History On August 6, 1945 the first atomic bomb was dropped by the USA on the city of Hiroshima. On August 9, 1945 a second atomic bomb was dropped by the USA on the city of Nagasaki. The USA wanted to end WWII with Japan and they thought that the best way to convince Japan to surrender was to drop atomic bombs on the two cities. The dropping of the bombs ended the war. But it also killed thousands of people. (1) www.bestanimations.com/Military/Explosions/Explosions.html

Creating the Bomb Robert Oppenheimer came up with the technology to construct the atomic bomb. The idea for the nuclear chain reaction came for Albert Einstein. Einstein urged President Roosevelt to research the nuclear bomb. They named the Atomic bomb project The Manhattan Project (1). 1heckofaguy.com

The Manhattan Project The Manhattan Project was mainly based in New Mexico and Los Alamos. Many scientists worked on the project like Philip Abelson's, Hans Bethe and Robert Oppenheimer. The first nuclear bomb test was on July 16, 1945 at a bombing range known as Trinity which is located in New Mexico. (2) www.bestanimations.com/Military/Explosions/Explosions.html historymike.blogspot.com

Fission The 1st bomb dropped on Hiroshima was nicknamed “Little Boy”. The 2nd bomb dropped on Nagasaki was named “Fat Man”. “Little Boy” was made of the isotope Uranium 235 and “Fat Man” was made of plutonium 239. The bomb used Fission. Fission is when a neutron hits a nucleus and splits it into two nuclei (1)

Nuclear Fission Nuclear fission - You can split the nucleus of an atom into two smaller fragments with a neutron. The isotopes you start with are uranium or plutonium. When a heavy atom undergoes nuclear fission it breaks into two or more fission fragments. Also, several free neutrons, gamma rays, and neutrinos are emitted, and a large amount of energy is released.(4)

Nuclear Chain reaction A nuclear chain reaction occurs when one nuclear reaction causes an average of one or more nuclear reactions, thus leading to a self-propagating number of these reactions. (4)

What is the difference between the nuclear reaction that happens in a nuclear power station and the nuclear reaction that happened in The Little Boy? www.atomicarchive.com http://science.howstuffworks.com/nuclear-power3.htm Basically, the way that the Little Boy was designed consisted of a gun that fired 1 mass of uranium-235 and another mass of uranium-235, thus creating a supercritical mass. It was necessary and required that the two pieces be brought together in a time that was shorter than the time between spontaneous fissions. Once the 2 pieces of uranium were brought together, the initiator introduces a burst of neutrons and a chain reaction starts, continuing until the amount of released energy becomes so great that the bomb simply blows itself apart! (5)

What is the difference between the nuclear reaction that happens in a nuclear power station and the nuclear reaction that happened in The Little Boy? When you hear about the Little Boy (and the Fat Man), you have immediately caught the thread of similarity now between these guys and the nuclear power plant – it’s the nuclear reaction which works underneath both of them. The only difference lies in the utilization of the energy generated during that reaction in a useful or a destructive manner. The bomb consisted of several kgs (little over 60 kgs) of Uranium-235 i.e. un-enriched uranium which was kept separated from a solid target spike. When the bomb was due to be detonated, conventional explosive materials forced them together and hence the mass would reach the supercritical range thus starting the chain reaction. These types of nuclear bombs were highly unsafe in that they could self detonate under various circumstances such as shock, crash, fire and so forth and hence this design is no longer in use. Moreover these weapons were very inefficient in that out of nearly 60 kgs of uranium, hardly less than a kg underwent fission and out of that hardly a few grams was converted into energy. But this should give you an idea of the power inherent in such a small mass energy convergence. (5)

Critical Mass Critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. (1) The critical mass of uranium 235 is 52 kg (6)

Size and Weight of “Little Boy” The weight of Little Boy is 4 tons. The size of Little Boy in length is 3 meters. (1) www.globalsecurity.org

How Fat Man and Little Boy were triggered Fat man was implosion-triggered Little Boy was gun-triggered. They weren’t triggered on the ground because the designs generated a destructive force. (3) www.atomicarchive.com

Devastation caused by Little Boy The bomb dropped on Hiroshima code named Little Boy went off with a force of 15,000 tons of TNT and had a blast radius of 1.5 miles. Little Boy killed 140,000 people in the initial blast (1) 1000needles.blogspot.com

Effects of Radiation Even after the explosion of the bomb thousands more died because of radiation poisoning Radiation destroys humans cells and causes cancer. (1)

Glossary Fission: the spontaneous or induced splitting of an atomic nucleus into smaller parts, usually accompanied by a significant release of energy. (1) Fusion: Two nuclei are combined to form a larger nuclei. (1) Manhattan Project: The project to developed nuclear weapons (1) Atomic bomb: An explosive weapon of great destructive power derived from the rapid release of energy in the fission of heavy atomic nuclei, as of uranium 235. (7) Nuclear Radiation: A term used to denote alpha particles, neutrons, electrons, photons, and other particles which emanate from the atomic nucleus as a result of radioactive decay and nuclear reactions. (7) Critical Mass: is the smallest amount of fissile material needed for a sustained nuclear chain reaction (1) Radioactive fallout: Fallout is the residual radiation hazard from a nuclear explosion, so named because it "falls out" of the atmosphere into which it is spread during the explosion. It commonly refers to the radioactive dust created when a nuclear weapon explodes. (7)

Bibliography Source #1 http://en.wikipedia.org/wiki/Atomic_of_Hiroshima_and_Nagasaki Source #2 http://www.cfo.doe.go/me70/manhattan/index.htm Source #3 http://science.howstuffworks.com/nuclear-bomb1.htm Source #4 http://wikipedia.org/wiki/Nuclear_chain_reaction Source #5: http://www.brighthub.com/engineering/mechanical/articles/3421.aspx Source #6: www.wisegeek.com/what-is-critical-mass.htm Source #7 :http://www.answers.com/topic/atom-bomb