Why can't light be in black color?

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Discussion Overview

The discussion revolves around the question of whether light can be considered to be black in color. Participants explore the nature of color, the perception of light, and the definitions of black in different contexts, including physics and human perception. The conversation touches on theoretical and conceptual aspects of light and color, as well as practical examples.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that black is interpreted by the human brain as the absence of detectable light, while others argue that it can be considered a color in the context of pigments.
  • There is a discussion about how color is perceived based on the light that falls on the eyes, with some noting that color blindness can affect this perception.
  • One participant mentions that in space, everything appears black except for stars, which leads to a clarification about the twinkling of stars being an effect of Earth's atmosphere.
  • Several participants debate whether black is a color, with distinctions made between additive (light) and subtractive (pigment) color models.
  • Some mention the existence of 'black lights' and clarify that these are actually UVA lights that cause fluorescence in other materials.
  • There are references to methods of achieving a very deep black using specific setups, such as a box lined with black velvet, which absorbs light effectively.
  • One participant proposes defining black as 0°K, suggesting a scientific perspective on the absence of light.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the definition of black and whether it can be classified as a color. The discussion remains unresolved, with no consensus on the nature of black in relation to light.

Contextual Notes

The discussion highlights the dependence on definitions of color and light, as well as the subjective nature of perception. There are unresolved distinctions between different models of color and the implications of those models on the understanding of black.

  • #61
You can define anything you want (that makes sense); such definitions are not "wrong".

In mathematics, a hole in a space is a very precise concept, that most certainly exists.

There is nothing wrong with defining darkness as the absence of light.

But do no confuse it with light, which carries energy and wavelength, can be a wave or particle, etc. Dark could be defined as the zero element in the (portion of) the infinite-dimensional Hilbert space that comprises all possible light rays. But it is different from the nonzero elements, in that it doesn't "carry" any information, since it doesn't "go" anywhere.

IF we wanted to make sense of "the speed of dark", that might actually make sense: Suppose we are continuously shining a light at a screen at a distance D away. Suddenly we turn of the light source; assume for simplicity that the light emission stops instantly. Then if as usual, c is the speed of light, the screen should stop reflecting light at a time equal to D/c later. So in this sense the speed of dark is the speed of light.
 
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  • #62
zinq said:
IF we wanted to make sense of "the speed of dark", that might actually make sense: Suppose we are continuously shining a light at a screen at a distance D away. Suddenly we turn of the light source; assume for simplicity that the light emission stops instantly. Then if as usual, c is the speed of light, the screen should stop reflecting light at a time equal to D/c later. So in this sense the speed of dark is the speed of light.

Now take that light source and sweep it across the screen. What is the maximum speed of the shadow/light spot across the screen?
 
  • #63
Sure, no maximum, but that's not dark "moving". Because, in no sense is the shadow at one location the "same" as the shadow at another location. Nothing moved, so no speed is relevant.
 
  • #64
Drakkith said:
What is the maximum speed of the shadow/light spot across the screen?

Musn't it be c, since we could never measure with any experiment that it were faster?
 
  • #65
If dictionary.com is an acceptable reference, then below citation should resolve the question of whether black is a color. ;-)

noun
20. the color at one extreme end of the scale of grays, opposite to white, absorbing all light incident upon it.
 
  • #66
Grinkle said:
Musn't it be c, since we could never measure with any experiment that it were faster?

Sure we can. Place two light sensors on the screen some distance apart from each other and then sweep the light across them. You'll find that the difference in the time that one sensor goes on/off and the other sensor goes on/off can be anything from 0, corresponding to just pointing the light source directly at the sensors and turning it on or off, all the way up to any value, corresponding to how fast you sweep the light source across the screen.

zinq said:
Sure, no maximum, but that's not dark "moving". Because, in no sense is the shadow at one location the "same" as the shadow at another location. Nothing moved, so no speed is relevant.

The only stuff that moved was the light on its trip from the light source to the screen. But that's not any different from your example. It still makes little sense to talk about the speed of darkness.
 
  • #67
Jon Richfield said:
Get real Dave! Read a book called The Shadow Club by Roberto Casato. It should make you more careful with such assertions.
A hint: before claiming that an entity exists or not, you should analyse its nature.
Would you say that a hole in the ground does not exist? Or a hole in a semiconductor?
back off Jon .. stop being obnoxious !
 
  • #68
I think this thread has gone on and off topic long enough. Since the original question has been beaten to death as well, I'm locking this thread. Anyone interested in the 'speed of dark' or something else in this thread can start a new one.
 
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