glowing

Glowing describes the emission of visible light by a substance or object. The light may be produced by heat (incandescence) or by luminescent processes that generate light without significant temperature rise. The term is used across scientific and everyday contexts to refer to steady light emission of various origins.

Incandescence occurs when objects are heated to high temperatures, causing them to emit light as a result of blackbody radiation. Color changes with temperature—from red to orange to white—reflecting the spectrum of emitted light. This glow fades as the object cools and is generally inefficient due to energy lost as heat.

Luminescence covers light produced without substantial heat. Major categories include:

- Fluorescence: light is emitted during excitation and ceases almost immediately after the excitation stops.

- Phosphorescence: delayed emission that can continue for milliseconds to hours after excitation.

- Chemiluminescence: light from a chemical reaction without much heat, as seen in glow sticks.

- Bioluminescence: light produced by living organisms via biochemical reactions, common in marine creatures and some insects.

- Electroluminescence: light generated by electrical current, as in LEDs and OLEDs.

- Photoluminescent materials (glow-in-the-dark): pigments that store light energy and re-emit it later.

Applications span safety signage and emergency lighting, consumer products and art, medical imaging and biological research, and various industrial indicators. Glowing phenomena thus encompass a range of mechanisms that produce light with differing temporal and energetic characteristics.