If a nuclear explosion renders the area uninhabitable for a half life of 2,500 years?
Then why are Hiroshima and Nagasaki thriving metropolitan areas?
Half-life is not a measure of how long it takes for an area to become clean after exposure to radiation. It is the amount of time that it takes for a given sample of a radioactive element to decay to half its original mass.
Here’s how it works: what makes radioactive elements radioactive is that their nuclei (the centre of the atom) are so large that they have difficulty staying together. Eventually, the nucleus (singlular of nuclei) of a radioactive element breaks up, or decays. When this happens, several protons and neutrons (the particles that make up the nucleus) go flying off at arond the speed of light – these are what make up the radiation. What’s left over is an atom with fewer protons. Since the number of protons in the nucleus is what determines the type of atom, once a radioactive atom decays (gives off protons) it becomes an atom of a different (lighter) element, like lead. Half-life is the length of time it takes for half of any sample to decay in this manner.
So if it takes so long to decay, how are people living in Hiroshima today? Because you don’t have to wait for it all to decay for the radiation to go away. The residual radiation is caused mostly by tiny particles of leftover radioactive material from the bomb. This radioactive dust lingers behind, continually emitting radiation. However, given time and clean-up efforts, the radioactive materials can be largely removed and life can resume.
Don’t let that make you think that nuclear war wouldn’t be the end of the world. WWII saw 2 little atomic bombs over the course of several days. A modern nuclear war would involve hundreds or thousands of nuclear weapons detonating around the globe over the course of a few hours, each more powerful than the 2 dropped on Japan.