Explore 20 common misconceptions about space with our myth-busting PXR64U6G75zxz5DuE6NooDe.
20 space myths busted! : Read more
20 space myths busted! : Read more
20 space myths busted!
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Nice list!
The Heliochromologist would note that there are two parts to the story as to why the Sun isn't yellow.
The statement, "The sun produces all wavelengths of visible light and therefore its true color is white, ..." But all stars, even red ones, produce all the wavelengths of light. This is a well-known fact that, surprisingly, gets ignored.
When making a cookie, it's not only the ingredients used, but the proportion of those ingredients that determines what it will taste like. Similarly, and the 2nd part of the color story, is found in the distribution of those colors. The eye receives about the same no. of photons (flux density) for any given wavelength across the visible spectrum. The eye interprets this as white.
The Heliochromologist would note that there are two parts to the story as to why the Sun isn't yellow.
The statement, "The sun produces all wavelengths of visible light and therefore its true color is white, ..." But all stars, even red ones, produce all the wavelengths of light. This is a well-known fact that, surprisingly, gets ignored.
When making a cookie, it's not only the ingredients used, but the proportion of those ingredients that determines what it will taste like. Similarly, and the 2nd part of the color story, is found in the distribution of those colors. The eye receives about the same no. of photons (flux density) for any given wavelength across the visible spectrum. The eye interprets this as white.
Actually, the brain interprets the signals from the different sensors in the eyes ("rods" and "cones" with different peak wavelength sensitivities) so that what is perceived as "white" can change by a large amount.
Incandescent bulbs are typically more yellowish, florescent bulbs are a bit greenish, and LEDs can be all sorts of strange combinations of wavelengths, some of which really make humans skin look weird.
This all used to be pretty obvious to people with film cameras, looking at slides taken under different lighting conditions with the same film. With automatic color "corrections" in digital cameras today, we are not noticing it as much.
So, I am thinking the real problem with this is settling on the definition of "white". Some creaturs that evolved on a planet orbiting a red dwarf would probably have an entirely different definition for the word. And so would terrestrial organisms that can see into the ultraviolet parts of the solar spectrum.
Incandescent bulbs are typically more yellowish, florescent bulbs are a bit greenish, and LEDs can be all sorts of strange combinations of wavelengths, some of which really make humans skin look weird.
This all used to be pretty obvious to people with film cameras, looking at slides taken under different lighting conditions with the same film. With automatic color "corrections" in digital cameras today, we are not noticing it as much.
So, I am thinking the real problem with this is settling on the definition of "white". Some creaturs that evolved on a planet orbiting a red dwarf would probably have an entirely different definition for the word. And so would terrestrial organisms that can see into the ultraviolet parts of the solar spectrum.
Yes, color perception is complex. The retinex (eye-brain processing) uses bright whitish sources to help color correct. “Color constancy” addresses this. Camera processors do this as well, which is why having a known white object in the image helps.
But, this effect pushes bright objects with a tint of color toward a more white, or completely white, result.
The yellow Sun hypothesis is easily falsified, and a white Sun is easier to argue partly for the above reason.
But, this effect pushes bright objects with a tint of color toward a more white, or completely white, result.
The yellow Sun hypothesis is easily falsified, and a white Sun is easier to argue partly for the above reason.
I am still seeing this as a matter of differing perceptions.
The physicists are looking at a spectral analysis, finding the peak intensity wavelength of the Sun's emissions, and calling that color "green" because when that color is shown to people independently of other light sources, people call it "green". But, the Sun also emits other wavelengths of light, too, and the "blues" and "yellows" are not in tiny amounts compared to the "greens".
In contrast, if you take those same people outside, and they see something illuminated by direct sunlight plus blue light scattered from a clear sky, what they are seeing is that the directly illuminated areas are yellower than the areas in shadow that are illuminated more by the scattered blue light from the sky.
Most people are used to combining pigments, not analyzing spectra. So, to most people, "green" is a combination of "blue" and "yellow" pigments. "Shades" of "green" can range from "yellowish" to "blueish". So, it is logical to infer that the Sun emits light that is "yellow" if it makes their perception of other objects move from "blueish" to "yellowish".
The subject article does point out that direct sunlight gets filtered in the atmosphere such that it looks more yellow on Earth's surface than in space. But, that is really a "red herring" (pardon the pun), because people did not evolve in space, we evolved on Earth's surface, where we learned what is "white" and what has "color" based on the light that actually reaches the surface.
The physicists are looking at a spectral analysis, finding the peak intensity wavelength of the Sun's emissions, and calling that color "green" because when that color is shown to people independently of other light sources, people call it "green". But, the Sun also emits other wavelengths of light, too, and the "blues" and "yellows" are not in tiny amounts compared to the "greens".
In contrast, if you take those same people outside, and they see something illuminated by direct sunlight plus blue light scattered from a clear sky, what they are seeing is that the directly illuminated areas are yellower than the areas in shadow that are illuminated more by the scattered blue light from the sky.
Most people are used to combining pigments, not analyzing spectra. So, to most people, "green" is a combination of "blue" and "yellow" pigments. "Shades" of "green" can range from "yellowish" to "blueish". So, it is logical to infer that the Sun emits light that is "yellow" if it makes their perception of other objects move from "blueish" to "yellowish".
The subject article does point out that direct sunlight gets filtered in the atmosphere such that it looks more yellow on Earth's surface than in space. But, that is really a "red herring" (pardon the pun), because people did not evolve in space, we evolved on Earth's surface, where we learned what is "white" and what has "color" based on the light that actually reaches the surface.
I've never heard claims of a green Sun. Stars (ignoring color contrasting doubles) won't look green since the other colors combine with it to prevent a green result.
Here is a site that addresses star colors, but it is based on computer modeling, which I find to be inaccurate, due in part to what we mentioned above - color constancy. My avatar is a photo taken from the projection table at Kitt Peak. The color pieces are to demonstrate color accuracy. It is amazing to me that white is rarely represented for any star color, much less the Sun.
Why the Sun has no tint of yellow can be demonstrated in two sentences.... This avatar image is a post-atmospheric image with extinctions, which are predominantly in the blue end of the spectrum. Adding those color extinctions into the white image will never produce a yellow image, even along the limb (if observed with proper attenuation from space).
If we take the known spectral irradiance of the Sun (AMO - zero atmosphere), and convert this to a photon flux (density) distribution, then the following is the result...
View: https://imgur.com/a0p9V3R
[This is actually my presentation taken from the ref. data stated.]
The blue-end photons have a lot more energy than the red-end, thus, using E=hv, the net effect produces a surprisingly flat spectral flux.
Right. I find that the white sheet of paper appears to have a strong tint of blue. I think it would still appear to have this tint if I was in a dark enclosed room with only this projection. This demonstrates that color constancy has its limits on causing us to see a white result.
I like to compare a non-halogen car headlamp as seen in bright daylight with how it looks at night. The shift from yellow to a yellowish-white is distinctive. Daylight is the reference source, making lower temperature lighting more yellow. But at night, the reference light is pushed to be the "white" reference light, allowing for better color correction of other objects.
The only time I see a hint of yellow for a noon-day Sun is in a very quick glance that, for some reason, can give the limb a yellowish appearance. But the intensity of direct sunlight is roughly 10,000x brighter than the limits of the photopic range for normal color determination.
Also, a pin-hole solar projection of a noon-day Sun will produce a white disk, assuming particle counts aren't too bad. [I've seen a white star appear yellowish-white even from a high altitude (McDonald Obs.) due to a very high particle count of pollens, etc.]
That certainly seems reasonable, but evolution is passive, so the eye's of other animals see things differently when it benefits them. I won't forget a night time visit to my telescope and finding a 5' rattlesnake next to it during its nocturnal activities.
The story that needs telling is why science ever accepted a yellow Sun idea. Science is clear that this is an atmospheric effect, so why extend it to space, especially given all the white results from solar observatories. The answer, IMO, lies with those in the late 19th century who recognized the importance of spectral classifications. The Sun's spectrum was close to other yellow-appearing stars (e.g. Capella) and it got lumped in that group and stayed there.
Perhaps the yellow Sun error is another example why science by consensus should not be seen as hard science at all.
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Helio, the first thing I need to note is that the peak of the graph that you show in your last post is in the yellow range! There seems to be some difference in looking at the solar wavelength output as energy in a frequency band or number of photons in a frequency band. Because the photons have more energy at higher frequencies, the color of the peak in the two different presentations is shifted.
Sensors that are sensitive to a limited range of frequencies will not tell us how many photons are in other frequencies. And, if there is an array of sensors with 3 different sensitivity ranges (as in our eyes), they need not all be calibrated to the exact same sensitivity with respect to number of photons nor the total energy of the detected photons. That is true for eyes as well as lab sensors.
Some people can close one eye and look at a scene, then open that eye and close the other one, look at the same scene, and notice 2 different color intensity distributions. I found that out while working to adjust my binoculars to have both eye pieces in focus at the same distance in a sunlit scene. One of my eyes sees things a tad more blueish and the other a tad more yellowish. Yes, at first I thought there was something wrong with my binoculars, but I repeated the experiment without them, and I can noticeably change the color tint by winking my eyes back and forth. Some others have the same condition. It is not surprising, since some people are even "color blind" in that they cannot distinguish between red and green or between blue and yellow, but still see some colors, and some do not see any colors.
As for the sun being "green", here is a link that says the peak solar wavelength comes out between 483 to 520 nm, which puts in the the region between blue and green in the image you included in your post. https://hypertextbook.com/facts/2002/TahirAhmed.shtml That does not mean that it should look green. But, it is an argument that people could choose to have (or, better, choose to not have).
I am not sure what you intended with your remark about the rattlesnake near your telescope at night. A rattlesnake is a "pit viper", named for the pits on its face that can sense infrared light in the range emitted by warm-blooded animals. That is just another set of photon sensors that is completely independent of the snake's eyes, that let's it "see in the dark" as humans perceive that ability. So, if you ever find a talking rattlesnake, please ask it what it thinks is "white" and what it thinks is "yellow".
Anyway, I am of the opinion that the original article has only "busted" 19 "myths", not 20. This one is definitely "in the eye of the beholder" or maybe the mind.
Sensors that are sensitive to a limited range of frequencies will not tell us how many photons are in other frequencies. And, if there is an array of sensors with 3 different sensitivity ranges (as in our eyes), they need not all be calibrated to the exact same sensitivity with respect to number of photons nor the total energy of the detected photons. That is true for eyes as well as lab sensors.
Some people can close one eye and look at a scene, then open that eye and close the other one, look at the same scene, and notice 2 different color intensity distributions. I found that out while working to adjust my binoculars to have both eye pieces in focus at the same distance in a sunlit scene. One of my eyes sees things a tad more blueish and the other a tad more yellowish. Yes, at first I thought there was something wrong with my binoculars, but I repeated the experiment without them, and I can noticeably change the color tint by winking my eyes back and forth. Some others have the same condition. It is not surprising, since some people are even "color blind" in that they cannot distinguish between red and green or between blue and yellow, but still see some colors, and some do not see any colors.
As for the sun being "green", here is a link that says the peak solar wavelength comes out between 483 to 520 nm, which puts in the the region between blue and green in the image you included in your post. https://hypertextbook.com/facts/2002/TahirAhmed.shtml That does not mean that it should look green. But, it is an argument that people could choose to have (or, better, choose to not have).
I am not sure what you intended with your remark about the rattlesnake near your telescope at night. A rattlesnake is a "pit viper", named for the pits on its face that can sense infrared light in the range emitted by warm-blooded animals. That is just another set of photon sensors that is completely independent of the snake's eyes, that let's it "see in the dark" as humans perceive that ability. So, if you ever find a talking rattlesnake, please ask it what it thinks is "white" and what it thinks is "yellow".
Anyway, I am of the opinion that the original article has only "busted" 19 "myths", not 20. This one is definitely "in the eye of the beholder" or maybe the mind.
Yes, but it's not a peak, but a pimple!
[Irony is alive and well. ]Yes, and the sp. irr. (AM0) is very strong in the blue end of the spectrum, also contrary to many reports, surprisingly. The difference in wavelength is almost double for violet vs. far red, so the blue end drops dramatically for a photon flux distribution.
I have to leave, but I hope to get back to the rest of your post tomorrow.
UNC..."Yes, at first I thought there was something wrong with my binoculars, but I repeated the experiment without them, and I can noticeably change the color tint by winking my eyes back and forth. Some others have the same condition. It is not surprising, since some people are even "color blind" in that they cannot distinguish between red and green or between blue and yellow, but still see some colors, and some do not see any colors."
Right, but I am going on the assumption that what is seen as, for example, a saturated red for an apple, will be very similar to the vast majority of other's color perception. There is some science that seems to verify this view, but I haven't looked into it much as it gets deeper than I want to go.
Your evolutionary viewpoint, however, does suggest that we could define "white" as the color emitted by the Sun, as seen a 1 Atm. I also think that we could simplify it and just use a flat photon flux spectral distribution as a definition, though no such definition seems all that necessary since we have all gotten things done without this technical definition.
Of course, I would be tickled just to see people quit calling the Sun yellow!
Right, but I am going on the assumption that what is seen as, for example, a saturated red for an apple, will be very similar to the vast majority of other's color perception. There is some science that seems to verify this view, but I haven't looked into it much as it gets deeper than I want to go.
Your evolutionary viewpoint, however, does suggest that we could define "white" as the color emitted by the Sun, as seen a 1 Atm. I also think that we could simplify it and just use a flat photon flux spectral distribution as a definition, though no such definition seems all that necessary since we have all gotten things done without this technical definition.
Of course, I would be tickled just to see people quit calling the Sun yellow!
Lots of problems with this article.
"Do black holes suck matter into their cores? Nope." Oh yes, they do. From Wiki: "Observers falling into a Schwarzschild black hole (i.e., non-rotating and not charged) cannot avoid being carried into the singularity once they cross the event horizon."
"700 million tons of hydrogen smash together to form 650,000 tons of helium"
That probably should be 650 million tons of helium.
"Sir, the possibility of successfully navigating an asteroid field is approximately 3,720 to one" That is an extrremely high probability of success. So it applies equally well to our asteroid belt.
"3.8x1026" should be 3.8x10^26.
"Do black holes suck matter into their cores? Nope." Oh yes, they do. From Wiki: "Observers falling into a Schwarzschild black hole (i.e., non-rotating and not charged) cannot avoid being carried into the singularity once they cross the event horizon."
"700 million tons of hydrogen smash together to form 650,000 tons of helium"
That probably should be 650 million tons of helium.
"Sir, the possibility of successfully navigating an asteroid field is approximately 3,720 to one" That is an extrremely high probability of success. So it applies equally well to our asteroid belt.
"3.8x1026" should be 3.8x10^26.
Does it "suck"?
Do we walk on the Earth's surface because of a sucking action? We do like hyperboles to help us, so I could see some use now and then for that inaccurate but somewhat effective use.Yes. Good catch! I think the numbers are more like 670 million tons of hydrogen converts to 665 million tons of helium. The 0.7% difference is the energy released.
There are some other tweaks needed on those numbers related to the asteroid belt.
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