A "half-life" is the amount of time it takes for half of a substance or entity to undergo some specified process. In nuclear chemistry, (radioactive) half life is defined, for a simple radioactive decay process, as the time required for the activity to decrease to half its value by that process. However, the phrase "half life" can be applied to other things aswell, such as the biological half life of a substance refers to the "time at which the amount of a biomolecule in a living organism has been reduced by one half". The phrase "half life" has also been used in finance and marketing :
"In marketing, half-life is a formula for estimating the total responses to be expected from a direct marketing campaign. The half-life of a catalog is the day when half of the consumer responses to the mailing have been received. Sears Canada studied the history of their sales data and found that their catalogs reached their half-life 20 days after being mailed, although the life of the catalog was actually several months. Knowing when a direct marketing campaign reaches the half-life point allows marketers to adapt more quickly to consumer demand. "
"In finance, the half-life of a mortgage is the date when half of the principal amount has been paid. Because of the way that interest is pro-rated (as a proportion of the total, paid more towards the first part of the life of the mortgage), the mortgage half-life date is generally more distant than the chronological half-way point in the total life of the mortgage. "
So you see, the term "half-life" does not only apply to nuclear chemistry but has been adopted by other fields of science as well. And if you do a search on google or wherever, you WILL see that proteins (casein, egg, whey etc) do have half lifes(a certain number of hours i think). I guess you can forego making fun of me.
Peace.
