Thermal imaging is one of the most recognisable techniques in modern paranormal investigation. The colourful images, shifting temperature patterns, and ability to "see" in darkness make thermal cameras feel like a natural partner to ghost hunting. Before relying on them for evidence, however, it's important to understand exactly what they're measuring and, just as importantly, what they can and can't detect.

This lesson explains the basic science behind thermal imaging, how the cameras convert invisible infrared radiation into a visible picture, and why this matters when you're trying to make sense of apparent temperature fluctuations on an investigation.44Every object above absolute zero gives off infrared radiation. The warmer it is, the more infrared it emits. A thermal camera doesn't record visible light like an ordinary camera. Instead, it detects this radiated infrared energy and converts it into a temperature-based image.

The lens of a thermal camera focuses those infrared waves onto a...