El comienzo y el final de un Ja, ja, ja"! Ja, ja, ja

Euro Murzi initiated the threads with: Do light and darkness exist? “Light and darkness” are created by the mind. They don’t exist in real world! In Physics does not exist “light”, but electromagnetic radiations. We call “light” the human visible spectrum, but the rest of the non visible spectrum how do we call it? The brain invented “light” or “darkness” to see or not to see the visible expectrum, but in “darkness” still are present radio, microwave, infrared, ultraviolet, X-ray, gamma ray, but not visible wavelengths! Then, “light” and “darkness” are different concepts depending of being bees, snakes or humans! Doc Al replay: The words 'light' and 'darkness' are 'mental' creations. But that doesn't mean that visible electromagnetic radiation doesn't 'really' exist. The various parts of the spectrum have different names. So? Sure, but we can still detect them. Just not with our naked eyes. Visible light is, of course, with respect to what humans can see. And even that varies. But sure, different creatures can 'see' different frequencies. Euro Murzi replay: Of course electromagnetic radiation exist, but not as “light” or “darkness”. These are not physical terms. “Visible” is not synonymous of existence! Then, do you accept that “light” is not a physical appropriate name? Then, why don’t we call undetect one as "light" as well? Then not call them “Visible light”, but visible electromagnetic radiation! That's the point! ryan_m_b replay: I think you are confusing the issue. "Light" can refer to a multitude of things, it can mean a photon or stream of photons. It is also a relative measure of how well lit something is which is in turn a relative measure of how well we can see something. How well we can see something is determined by how much light there is. Light colloquially means visible light or to put it another way the part of the electromagnetic spectrum that is detectable by our eyes. In a more technical sense light can mean any frequency. You have stumbled upon the common mistake of trying to explore the meaning of a word whilst applying only one of multiple meanings. Euro Murzi replay: Nooo, my points is: see “clear and light” or “no light and darkness” is not physical but mental creation; physically “light and darkness” does not exist! As you say, colloquially they means visible or non-visible, respectively, but, insist, no physically! For example, “black is the sensation produced by the absence of light, but it is probably a positive sensation, because the blind eye does not “see black”; it “sees nothing.” (Med. Physiol. W. Ganong) ZapperZ replay: This is not a physics discussion. This is semantics, rather than a science issue. Unless there is a physics content here, this will be moved to the General Discussion forum. ryan_m_b replay to Euro Murzi: Light physically exists as photons. We sense light through the rod and cone cells in our eyes, these are physical processes that are real, not imaginary. Whether or not something is light or dark is a subjective measure but it is also real. We can quantify how bright an object is and we can say that this object is relatively brighter than some objects and relatively darker than others. Euro Murzi replay: I’m not saying photons are not real or imaginary, what I want to say is presence or absence of photons no necessary is light or dark, respectively. “Light or darkness” is not physically presence or absence of photons, they are perceptions! Photons can be radio, microwave, infrared, ultraviolet, X-ray, gamma ray, and visible ones, but the only you can see as light are the latest. So, “darkness” is not physically photon absence, is mind black creation for the absence of the visible ones, no for all of them! So, “light, darkness or sound” concepts do not exist in the real word, because in the real word only exists photons or molecular air vibrations! “When a tree falls, it produces a physical change detectable by the human ear, but "sound" is not a physical entity. Rather, it is the psychological interpretation of a physical entity, a phenomenon created by our brains. Since no one is present in the forest to hear the tree falling, there is no brain to "create" the sound. Technically speaking, then, a tree falling in the forest with no human there to observe it, makes no sound but vibrations.” ryan_m_b replay: As people have pointed out you are just playing a semantic game, light and dark are relative measures of difference in the luminosity of objects/places. The fact that these are extrinsic concepts rather than intrinsic characteristics is obvious and well known. Just because a definition exists separate to the object or objects in question does not make it non-existent. It exists as a qualia in the minds of those who define it. Since the mind is an emergent property of the physical it stands to reason that concepts exist in as much as the mind does. ZapperZ replay: Can you show me why this is important? I mean, is there some sort of a confusion going around that I'm not aware of in the field of physics where this needs to be straighten out? Other than an exercise in semantics, I am not aware of this being an issue at all in physics. Is there a reason you're bringing it up? my_wan replay: This OP had me doing a facepalm or two. But I believe I got the point in post #9. Basically all Euro Murzi appears to be saying is that like sound, which exist only as a verb in another presumably ontologically real medium, light is only real in the sense that it is a verb in something else. Euro Murzi, these ontological issues are discussed and debated in many different interpretive context. Your claim is nothing new and embedded in many different interpretations. To proclaim an ontological status of some singular aspect of nature authoritatively as if the ontology itself was absolute is not useful nor meaningful. If you had simply asked there are any number of models we could point out that make use of similar ontologies, but instead this was proclaimed. Ontologies are more varied that what "exist" and "not exist" can convey even. Your naked proclamations are of no value to anybody. Euro Murzi replay to ZapperZ: The reason is this: In the Neuroscience book edited by Purves et al. (page 232), it can be reading: “The reason for this unusual arrangement (rods and cones are active in the “dark” and inactive in “light”) compared to other sensory receptor cells is not known”! This unusual arragment, is because human beings could “see” places where come from few photons as a cave entrance or not “visible” photons from black painted surfaces, and brain use the following trick: 1.- When none or few visible photons are reaching the retina (“dark state”), rods and cones are active and releasing their transmitter to produce the sensation of “Darkness”; dark or black is a positive sensation because the blind eye does not “see black”; it “sees nothing” (W. Ganong in Medical Physiology, 22 edition, page 163). 2.- When some but still few photons reach the retina ("weak light"), rods will inactive and produce the sensation of nocturnal vision (without color sensation). However, cones keep still active. 3.- When a lot of photons reach retina ("strong light"), cones also will inactive and produce the sensation of diurnal vision with color sensations, while rods will saturate. In other worlds, “dark” is working as a “background”, “filling” or “stuffing” in the visual field, otherwise, poor illuminated areas or objects will see, not “dark”, but invisible! Dark is a brain trick to filling the areas where no "visible photons" come from! In poetic words: “Photons write on the retina, as a chalk on a blackboard”! “Dark” or “light” are not physical terms, they are mental sensations! As a Physics, we must say, instead "being in the dark or light", being in absence or presence of weak or strong amounts of photons! my_wan replay: Euro Murzi, these brain studies from neuroscience and psychology are interesting. Most of what you perceive as sensory data is actually constructed in your head, and know how to take advantage of this can fool people into all kinds of weird experiences. Yet there is a reason we can know that our brains lie to us about sensory data. It is called science, and sensory function does not give us an a priori foundation to make ontological claims about light. ryan_m_b replay: It seems like you are trying to say that in the presence of photons the light receptor cells are not active. This is not the case, the light receptor protein rhodopsin breaks down when photons hit it to cause a sensory stimulus. When there is not enough light (i.e. the intensity of photons is to low) there will not be sufficient stimulus in the eye, hence our brain will perceive darkness. As you mentioned this could occur if we were looking into a cave entrance, the area around the cave may be lit up but the inside can appear dark. However this does not mean that darkness does not exist. What we sense is a difference in the intensity of light in a certain range of the electromagnetic spectrum, as a relative measure when something is "darker" it is less bright than something that is "lighter". Colloquially we use the term "dark" to mean "when light levels are so low we have poor or non-existent vision". In physics (or any other walk of life) we have no need to change our colloquial definitions simply because they represent concepts rather than realities. It would be impossible for human language to do this, the very concept of names and numbers rely on our ability to use abstract concepts rather than descriptives of intrinsic characteristics. DragonPetter replay: Originally Posted by Euro Murzi View Post "As a Physics, we must say, instead "being in the dark or light", being in absence or presence of weak or strong amounts of photons!" That's just one way to say it. We don't talk like this, and saying in light or dark is valid even in a technical physics discussion since it implies absence or presence of photons. We don't have to talk in technicalities to express physics concepts. Doc Al replay: So you are talking neurobiology, not physics. Right? DragonPetter replay: He is all over the place :) I think its pointless to discuss it any further.. Euro Murzi replay: Nooo, I am talking physics; my point is: “dark, cool, salted, colorful, etc., etc” are not physicals concepts, but mentalist! If they are mentalist, they don’t exist in the real world, and therefore physics must not use to express any physical idea but colloquial! Then, "Do light and darkness exist?" Ja, ja, ja Doc Al replay: Nonsense. You're talking semantics, not physics. When I shine my laser on the wall I couldn't care less what anyone's mental state is. There's no ambiguity in my saying that I've turned the light on. (Even if I have my eyes closed!) Euro Murzi replay: When you cannot work as a physic with “dark or light, cool, salted, colorful, etc., etc” as physical entities but rather with intensity of photons, molecules concentration, wave lengths, respectively, is because semantic? Euro Murzi replay again: Well, let’s take away the term light because “your laser”, but it is not the same with “darkness”! Darkness is not a real entity, darkness is a mental creation to supply the diminution or absence o “human visible” electromagnetic wave length! In the context of “darkness” as absence of something, “light” by contrast is the same, but I never had said that photons do not exist! Possibly Terminator can see “visible” photons without “light or darkness” ingredients! Ja, ja, ja What it doesn’t exist is “light”, or “cools, salted, colorful, etc.”, entities! If you could see infrared waves in a very “dark night” to normal people, how could explain them, it’s but not is a “dark night”? ja, ja, ja ryan_m_b replay: Nobody is saying that darkness is a physical entity! It is a conceptual description of the luminosity of an object. Char.Limit replay: Well, this thread is interesting. micromass replay: "Well, this thread is interesting." Interesting in the sense that I get a headache from it... To say something on topic: of course light and darkness are subjective. But in physics, these terms are well-defined! I am become the supreme onion, the saddener of worlds All the truth in the world adds up to one big lie. micromass replay: Taking it philosophically, why should we be certain that reality exists. You're watching your computer now, but why does it exist? You're typing on your computer, but all you're feeling is your own neurons, nothing tells you that your computer exists. Maybe nothing exists except your own mind?? Bulletin Message You have been banned for the following reason: trolling is not allowed ja,ja,ja End of the threads!