Age of the Earth research. Most geological samples from Earth are unable to give a direct date of the formation of Earth from the solar nebula because Earth has undergone differentiation into the core, mantle, and crust, and this has then undergone a long history of mixing and unmixing of these sample reservoirs by plate tectonics, weathering and hydrothermal circulation. All of these processes may adversely affect isotopic dating mechanisms because the sample cannot always be assumed to have remained as a closed system, by which it is meant that either the parent or daughter nuclide (a species of atom characterised by the number
The Dog and Its Reflection The Dog and Its Reflection The Dog and its Reflection (or 'Shadow' in several translations) is one of Aesop's Fables and is numbered 133 in the Perry Index. An indication of how old and well-known this story was is given by an allusion to it in the work of the philosopher Democritus from the 5th century BCE. Discussing the foolish desire for more, rather than being content with what one has, he describes it as being 'like the dog in Aesop's fable.' In the story, a dog that is carrying a stolen bone, or piece of meat or cheese, looks