What are ghosts? And what are the names like, poltergeist, residual, etc.

Ghosts can be any sort of ghastly being and supposedly can be from any living animal. Poltergeists are a type of ghost that possess a whole house, they could be anything from a mass collection of spiritual energy to a very angry spirit.  

Explanation:

- "the past is made of multitudinous items ranging from anything that can be collected, recollected or assessed to originate in the past. as such, the past is a gallimaufry of particulars that may not have been related in any way. however, the human mind seeks organization to understand concepts and other things. the human mind therefore seeks relationships in explaining and studying the past. history being a humanity, dictates that historians have to serve this human trait by bringing structure to details of the past. historians do this by creating interpretive frameworks that capture as many details as possible."

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radioactive dating, also known as  radioisotope dating  is a process that in  estimating the approximate  age  of  rocks. these data can be analyzed from  the studies dealing with the  decay of the radioactive elements that are present in these rocks. in nature, there are a few types of materials or atoms which are quite unstable and they spontaneously decay or breakdown to form other kinds of atoms.