After the Chernobyl accident of 1986 and the Fukushima Daiichi accident of 2011, radioactive materials, called radionuclides, spread into the air, soil and water. Many decayed fast and vanished, such as iodine-131, which halves every eight days. Others, such as cesium, strontium and plutonium, stayed for years. How they harm depends on chemistry: cesium behaves like sodium and potassium and builds up in tissue, while strontium behaves like calcium and goes to bone. Weather and landscape decide where they travel, and measurements of soil, water and food let people find and control the risks, including in contaminated foods.

Hampi is a UNESCO World Heritage Site in Karnataka, India, with more than 1,600 surviving remains spread over 4,100 hectares. It was the capital of the Vijayanagara Empire from 1336 to 1565. Travellers from Persia and Portugal described it as a prosperous, wealthy and grand city with temples, markets and farms along the Tungabhadra River. By 1500 it was estimated to be the world's second-largest city after Beijing, and probably India's richest at the time. In 1565 a coalition of Muslim sultanates defeated the Vijayanagara Empire, its capital was conquered and destroyed, and the city was left in ruins. Hampi remains a religious centre, with the active Virupaksha Temple at its heart.