Thermal radiation comes not only from radioactive material; all objects with a temperature give off heat, known as thermal radiation. Everything gives and takes in thermal radiation, according to University of New Mexico's Physics Department. When an object gives off more heat than it receives, it goes through a "cooling" process. Eventually, two objects with different temperatures will heat and cool until they reach equal temperatures called equilibrium.
Most of the time, heat exists in an invisible part of the spectrum to the naked eye called "infrared," reports the University of New Mexico. As something heats up, like a metal coil on a stove, it shifts to the visible part of the light spectrum. Objects turn from a darker red, all the way up to blinding white light, like in a nuclear explosion. The type of material also determines how much heat radiates from an object.
The effects of thermal radiation usually have a bad mental image, especially because of the existence of nuclear weapons. A nuclear explosion contains extreme amounts of heat, up to 100 million degrees Celsius in most cases, according to AtomicArchive. The explosion of a nuclear weapon produces thermal radiation that can burn skin and damage eyes from several miles outside of the blast radius, according to AtomicArchive.
One of the most harmful effects of thermal radiation is the ability to ignite materials, especially dry matter like newspaper and flammable substances. It takes a lot of thermal radiation to ignite a material. AtomicArchive states that the amount of damage thermal radiation causes in a heat radius depends on the presence of obstacles that can absorb some of the thermal pulse, like cloud cover or a wall barrier.
Thermal radiation is not bad and is actually essential to every living creature. The sun emits thermal radiation all the time to warm the earth, according to Encyclopedia Britannica. Without thermal radiation from the sun, the earth would be far too cold for most life. You can even create thermal radiation in your own home to warm yourself, such as using a fire in a chimney.