Half-life n. (Physics) The time it takes for one-half of a substance decaying in a first-order reaction to be destroyed. For radioactive substances, it is the time required for one-half of the initial amount of the radioactive isotope to decay. The half-lifeis a measure of the rate of the reaction being observed. For processes that are true first-order processes, such as radioactive decay, the half-life is independent of the quantity of material present, and it is thus a constant. The time it takes for one-half the remaining quantity of a radioactive isotope to decay will be the same regardless of how far the decay process has advanced. Some chemical reactions are also first order, and may be characterized as having a half-life. However, for chemical reactions the half-life will depend upon temperature and in some cases other environmental conditions, whereas for radioactive isotopes the rate of decay is largely independent of the environment.
... were not vital; and a great while it would take for the earth within their pyramid to receive back the life-elements. And we told them certain ways by which they might bring a more speedy life to the soil; and this they were eager to do, being freshly alive after so long a time of half-life. ... — The Night Land • William Hope Hodgson Read full book for free!
... "What's the half-life of that stuff in the freighter?" I asked Orrin. I knew, but I wanted Goil to know too. ... — Jack of No Trades • Charles Cottrell Read full book for free!
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