Question: what are nuclear bombs made from and how can it blow up so much of an certain area .e.g Hiroshima

Aisling Kerr answered on 16 Nov 2015:

Nuclear bombs are made from either plutonium or uranium. When the nucleus of one of these materials is hit with a fast moving neutron, it splits into two lighter nuclei and two neutrons. It also releases energy in the form of heat and light. This process is called fission. In a reactor when one nucleus fissions, the emitted neutrons will go on to collide with two other plutonium or uranium nuclei, making them fission and release more 4 neutrons. These four neutrons will collide with four other nuclei and so on. So each fission reaction doubles the amount of neutrons being emitted and doubles the amount of energy being released. This is called a chain reaction. After only a few microseconds, there is the same amount of energy being released as thousands of tons of TNT. It was one of these atomic bombs that was dropped on Hiroshima. When the bomb goes off the blast radius depends on few things – where the bomb was detonated and how much material was in it. Two things cause this damage radius, blast energy and thermal energy. Blast energy is caused by the high temperature and radiation forcing gas in the atmosphere to expand rapidly creating a shock wave. This is what crushes objects and destroy buildings. The thermal energy is electromagnetic energy (light), and causes an intense burst of heat radiation. This is hot enough to burn and can cause things to catch fire. These two combined cause a lot of damage to the surrounding area.