Radiometric dating parent daughter isotopes
It's simple: You must have started with a total of 80 chips, because you now have 70 10 = 80 total additives to your ice cream.
Because your roommate eats half of the chips on any given day, and not a fixed number, the carton must have held 20 chips the day before, 40 the day before that, and 80 the day before that.
Say a second friend who is aware of this arrangement visits and notices that your carton of ice cream contains 70 raisins and 10 chocolate chips.
She declares, "I guess you went shopping about three days ago." How does she know this?
Many substances, however, both biological and chemical, conform to a different mechanism: In a given time period, half of the substance will disappear in a fixed time no matter how much is present to start with.
Such substances are said to have a The utility of this lies in being able to calculate with ease how much of a given element was present at the time it was formed based on how much is present at the time of measurement.
Calculations involving radioactive isotopes are more formal but follow the same basic principle: If you know the half-life of the radioactive element and can measure how much of each isotope is present, you can figure out the age of the fossil, rock or other entity it comes from.
Scientists interested in figuring out the age of a fossil or rock analyze a sample to determine the ratio of a given radioactive element's daughter isotope (or isotopes) to its parent isotope in that sample.
As an analogy, say you find yourself wondering, "How warm (or cold) is it outside?This is because when radioactive elements first come into being, they are presumed to consist entirely of a single isotope.Imagine that you enjoy a certain kind of ice cream flavored with chocolate chips.Mathematically, from the above equations, this is N/N The trick is knowing which of the various common radioactive isotopes to look for.
This in turn depends in the approximate expected age of the object because radioactive elements decay at enormously different rates.
You also need to know when you can or cannot apply a particular type of device to the task at hand; for example, if you want to know how hot it is on the inside of an active wood stove, you probably understand that putting a household thermometer intended to measure body temperature inside the stove is not going to prove helpful.