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PHYSICS

Radioactive Decay Sandbox

Pick a radioactive isotope — Carbon-14, Cesium-137, Polonium-210, Uranium-235 — and watch atoms decay probabilistically on a canvas. Real physics, accelerated for your viewing.

80
10200
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Select an isotope and start the simulation

Iodine-131

Medical imaging & thyroid therapy

Half-life: 8.0 days

Atoms remaining0 / 80—
Half-lives elapsed—since simulation start
Simulated time—real-world equivalent
Activity—decays per second
Safe in (10 half-lives)80.2 dayseffectively inert at ~1/1024
StatusReady80 atoms loaded
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The Radioactive Decay Sandbox is a visual physics simulation. Select any isotope from a curated list, set your initial atom count, and watch the simulation run — atoms decay according to true quantum probability, not a deterministic countdown. Each decay event flashes. The curve updates. The real-world context tells you what this isotope is used for and how long it takes to become safe.

How to Run the Decay Simulation

  1. Select a radioactive isotope from the list. Each entry shows its half-life and real-world application.
  2. Set the number of atoms (10–200) and choose a simulation speed. Click Start.
  3. Watch atoms decay on the particle canvas — each flash is one nucleus disintegrating. The stats panel updates in real time.

Frequently Asked Questions

Is the decay simulation physically accurate?

Yes — each atom decays independently with probability P = 1 − e^(−λΔt) per time step, where λ = ln(2) / half-life. This is the quantum mechanical basis of radioactive decay: each nucleus has no memory of how long it has existed, making every decay statistically independent.

What is a half-life?

A half-life is the time after which exactly half of a radioactive sample has decayed — on average. Carbon-14 has a half-life of 5,730 years, which is why it can date organic material back 50,000 years. Iodine-131 has a half-life of 8 days, which is why it clears the body quickly enough to be used in medical imaging.

How is the simulation time-accelerated?

For short-lived isotopes like Iodine-131, each simulation frame represents a fraction of a real day. For long-lived isotopes like Uranium-235, each frame represents millions of years. The speed slider adjusts the time-per-frame multiplier, allowing you to witness the full decay arc of any isotope in seconds.

Why does decay look random?

Because it is. Radioactive decay is one of the purest examples of quantum randomness in nature. No force, temperature, chemical state, or history affects when a specific nucleus will decay. Each atom 'decides' independently, moment to moment, with no memory of the past.