The term comes from the scientific fields where it means the amount of time it takes for half of something to undergo a process or the amount of time it takes for half of the atoms of a radioactive substance to disintegrate.
Also called life expectancy or shelf life, the time it takes for a data-storing medium to lose half of its strength. Floppy disks and magnetic hard drives have a half life of between five and seven years. Optical media, such as CD-Rs, have a half life of about 30 years.
