Radioactive substances give off protons (positive particles) and neutrons (neutral particles) at a steady rate.
Eventually, these substances change into different elements. For example, an isotope of uranium, U-238, will eventually decay into an isotope of lead.
Have they ever bothered to actually try to help survivors?
Very often historical evidence is found in layers and older layers are further down that the top layers.
And for the first time, the larger world begins to come into focus: her life with Martin is neither safe nor sustainable.
Motivated by her first experience with real friendship and a teenage crush, Turtle starts to imagine escape, using the very survival skills her father devoted himself to teaching her.
Radiometric dating, based on known rates of decay of radioactive isotopes in objects, allows a specific age of an object to be determined to some degree of accuracy.
Relative dating is a scientific process of evaluation used to determine the relative order of past events, but does not determine the absolute age of an object.