[delfinom]

IR isn't just super red light, it's heat. Lol

[rcxdude]

So is regular light, in that sense. The IR that's used for this kind of application is 'near infrared', which is much closer to light than the IR emitted by most warm objects.

[erik_seaberg]

It's light, and some animals can see it, just not us. https://en.wikipedia.org/wiki/Infrared has some pictures from the right kind of cameras and telescopes.

[svachalek]

It is the primary frequency of black body radiation at Earthly temperatures. But it is not the heat itself.