Your own body fizzes with thousands of radioactive decays every second
A typical person carries about 0.017 grams of potassium-40, enough to produce roughly 4,400 atomic decays each second. In SI terms that is 4,400 becquerels. The unit is so tiny that scientists usually reach for kilo, mega or even exa prefixes to talk about anything real.
One becquerel means one radioactive disintegration per second, averaged over time, since decays happen at random rather than on a schedule. The name honours Henri Becquerel, who shared the 1903 Nobel Prize in Physics with Pierre and Marie Curie for discovering radioactivity. The unit, together with the gray for absorbed dose, entered the SI in 1975.
Mathematically a becquerel is just an inverse second, so why not call it hertz? The answer is safety. Hertz is reserved for regular, periodic events such as waves. More importantly, writing prefixes onto a bare reciprocal second invites dangerous confusion: a micro-inverse-second works out to a million events per second, while a microbecquerel is one event every million seconds. Giving radioactivity its own name removes that trap. A name honouring Joseph Fourier was also floated before becquerel won.
Real-world figures show the range. The americium in a household smoke detector gives off about 37 kilobecquerels. Cosmic-ray neutrons striking nitrogen in the atmosphere make new carbon-14 at around one petabecquerel a year, and the planet's total stock of that isotope is put at 8.5 exabecquerels. The older unit, the curie, was pegged to one gram of radium-226 and equals 37 gigabecquerels; for a few decades a middle unit, the rutherford, equal to one megabecquerel, was also common.
A becquerel count on its own says nothing about harm. It measures how often a source decays, not how much radiation a person absorbs. Judging biological effect needs the dose actually received, which depends on the type and energy of the radiation, the geometry between source and body, and a weighting factor that rates alpha particles 20 times more damaging than beta.
Source: Becquerel
