Radioactive Decay Simulator
How to use the radioactive decay simulator
- A block of 1,000 atoms starts fully undecayed (blue). Each one has the same chance of decaying in any moment; decayed atoms turn dark.
- Watch the count fall by half every half-life and compare the jagged measured curve with the smooth N₀ × (½)^(t/T½) curve underneath.
- Pick an isotope to see the half-lives converted into real time, from minutes to billions of years.
Frequently asked questions
What is a half-life?
The time it takes for half of a sample of a radioactive isotope to decay. After one half-life half remains, after two a quarter, after ten about a thousandth. It is a fixed property of the isotope, unaffected by temperature, pressure or chemistry.
Why is the measured curve jagged?
Decay is random. Each atom decays independently with a fixed probability, so the number left at any moment fluctuates around the smooth exponential curve. With 1,000 atoms the fluctuations are visible; with a gram of material (10²¹ atoms) they vanish.
How is the half-life used in dating?
Carbon-14 has a 5,730-year half-life, so the fraction left in a sample gives its age: a quarter of the original carbon-14 means two half-lives, about 11,500 years. The Half-Life Calculator does the arithmetic, and the guide on how to calculate half-life explains it.
It says WebGL is turned off.
The 3D view needs WebGL, which every current browser has. It can be switched off by hardware acceleration being disabled in the browser settings, or by a very old graphics driver. Turn hardware acceleration on, or try another browser.
Is anything uploaded?
No. The simulation is drawn by your own browser with WebGL; nothing is sent anywhere, and it keeps working offline once the page has loaded.