# Is there still light in practical darkness? Do photons penetrate everywhere?

I always thought that, even in darkness, there would still be some light, making complete darkness, i.e. complete absence of photons as far as I know, just a theoretical thing. When I tried looking up whether or not this view was actually correct, I didn't find any clear information, however. Am I wrong?

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No, you are right. Anywhere you can go, you're surrounded by some kind of matter at some nonzero temperature. Though most matter is not quite a blackbody, it still does radiate when at finite temperature. However, at low temperatures the intensity of this radiation in the visible range vanishes proportional to $e^{-\frac1T}$, which means you normally have only few visible photons around, typically much less than those reflected in some indirect way from the sun or artificial light sources. You definitely can't see these photons with your eyes, because they are at a higher temperature as the surrounding and therefore have more thermal noise intensity.