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> So why do astronomy graduate students not know what color the Sun is? Without any proof, I will offer a guess: Because it is the wrong question! If you ask
by Hokusai 6y ago
> So why do astronomy graduate students not know what color the Sun is?
Without any proof, I will offer a guess: Because it is the wrong question!
If you ask "What is the wavelengths of the light than the sun emits?", you are setting an expectation of an accurate answer. "What color is the sun?" seems a casual question that expects a casual answer.
> White is unambiguously the correct answer.
Obviously false without knowing at what relative speed and in which direction the Sun moves relative to the observer. There are always different degrees of accuracy and expectations need to be set to get the correct answer.
- hedora 6y agoWhite is often defined to be the color of sunlight that reaches the earth’s surface (go look at lightbulb specs to see what I mean). That accounts for any relativistic and atmospheric issues.
- enkid 6y agoBut diffusion through the atmosphere can change that color. For example, at sunset or sunrise.
- jlokier 6y agoLightbulb specs often describe their white color in terms of color temperature, in Kelvin. This refers to perceptually matching the color of an ideal black body glowing at the specified temperature. The documented color temperatures of different lights vary considerably. Rarely do they match sunlight. Daytime, overhead sunlight at the Earth's surface has a bluer spectrum than most lightbulbs, but sunlight doesn't look bluish-white because color perception adjusts rapidly for ambient light, and sunlight is so bright it dominates even when it's seen indoors through a window.
- lern_too_spel 6y agoColor is an ambiguous term, but most people interpret it as it is used in human visual perception. Under that definition, the author is wrong. Outside the atmosphere, it will be perceived as white, but here on Earth, it will vary from yellow to red. The environment that the person receiving the question can assume is the environment they are asked the question in. Therefore, the most popular answer of yellow is correct.
- danellis 6y ago> here on Earth, it will vary from yellow to red If that were true, how would we ever see blue things?
- lern_too_spel 6y agoBy looking at things our visual cortex perceives as blue, typically by activating the blue photoreceptors more than others relative to objects that are not blue but also via negative after images and a number of other methods. Look at these blue hearts, for example: https://cdn.cpnscdn.com/static/blog/2015/02/greenblueheartsstriped.jpg https://cdn.cpnscdn.com/static/blog/2015/02/greenblueheartss... You seem to be making the mistake I specifically warned against of defining color by the distribution of wavelengths coming from the object. Once again, the definition of color is ambiguous, and most people will use the human perception definition. Purple things don't have to be composed of pure violet light.
- danellis 6y agoWhat activates blue photoreceptors?
- lern_too_spel 6y agoElectromagnetic radiation with wavelengths between 380 NM and 550 nm. What point are you getting at? It is as yet unclear whether you understood my point.
- danellis 6y agoI'm not making a point; I'm asking a question. If the light from the Sun were "from yellow to red", what would trigger our blue photoreceptors? And no, I don't understand your point. I don't see what it has to do with yellow-red light.
- happytoexplain 6y agoAgreed - this is the all-too-common willing ignorance of colloquial semantics to pedantically demonstrate a non-point.
- de6u99er 6y agoTrying to correct your answer to the question without reading the article. If the Sun would only emit one wavelength, you'd need an artificial light source to get white (R+G+B) light. The answer white is correct in regards of the visible light spectrum. But you need to add infrared and UV to it. Red and blue shift is relevant for objects that move relatively to us observers. E.g. other stars within our galaxy, or galaxy relative to other galaxies. Since we orbit the sun relatively slowly you won't notice significant red or blue shift here.