Hi All This is my first post here and I have a question that should be relatively simple to answer. I am engaged in a debate with someone at the moment on a scifi forum. My stance is this: "Dark" is not a "thing" - it is merely the absence of light. You can measure light intensity, light has a speed etc. Dark cannot be measured in that way. It is not tangible. Similarly, "cold" is not a "thing" - it is merely the absence (or lower amount) of heat. These words are used in every day language because it's easier than saying "the temperature of the outside medium is less than that inside this building" - instead we say "it's cold". Just as with darkness, we say "it's dark outside" rather than "there is not as much light outside as there is inside". I know it's a bit pedantic but I was hoping that someone could confirm this view? I've done some brief research but unfortunately for me, "wikipedia" is not an acceptable source of information and whilst I usually try to follow the sources wiki gives as leads, for the statements of dark and cold being merely descriptive or abstract terms, there are no citations :( I apologise if this is the incorrect forum but I couldn't find on that was centered around the EM spectrum. Thanks.