Come on, now, I thought everyone knew Krypton had a red sun. Superman apparently gets his powers from the lack of a red sun, since he seems to have them even in interplanetary space. At least I’m pretty sure he’s travelled to other star systems under his own power.
What happens if he goes to a binary system with both a red and non-red star? Does he lose his powers or not? Somehow I doubt this situation has ever come up…
Everyone in Japan knows that the sun is actually red. Get a 4-year-old Japanese child to draw the sun, and they’ll draw a red orb high in the sky.
I have to assume it’s yellow. I don’t recall any astronaut ever saying “by golly, when you get above the atmosphere and look at the sun, its green.” If it was anything but yellow surely it would have been mentioned.
I’d be astonished if Superman never had been to a double-star system, but I don’t know either way. As to the other, IIRC Superman derives his power from a yellow sun, but he can go quite a while without needing to recharge. In Champions terms, all his powers are fuelled through a big-ass END battery.
I have to commenmt on this – the OP isn’t really right. The atmosphere doesn’t “bend light making the sky blue and the sun yellow”. There is a bit of refraction going obn, but not much (except right at sunrise/sunset) – the sun is pretty much where it appears to be. I think that you’re thinking about the effect of atmospheric scattering, which preferentially scatters shorter wavelengths of light (the scattering is due to anything in the sky – Leonardo da Vinci correctly observed that light scattered by smoke is blue. But the bulk of the scattering is due to scattering by the molecules of atmospheric gases themselves) There’s also some absorption by gases in the atmosphere. This doesn’t much change the spectrum, though. The RCA Electro-Optics Handbook (p. 62) gives a nifty plot showing solar radiation above the atmosphere, a 5900 K blackbody, and solar radiation observed at ground level. They’re not all that different, especially within the visible regime.
Finally, sunlight is pretty close to white, but not exactly there. According to Warren Smith’s Modern Optical Engineering, the standard illuminant B, representing noon sunlight, has CIR Chromaticity coordinates of (0.348, 0.352), placing it slightly to the yellow side of white. Illuminant C, average daylight, has coordinates (0.310, 0.316), making it slightly to the blue side of white. For comparison, Illuminant A (2848 K tungsten lamp) has coordinates (0.448, 0.408), making it a pretty obvious yellow (If you run it hotter, it becomes more like a blackbody and a hotter blackbody, and it’ll get whiter). So noontime sun is slightly yellow, but the abverage light from the sky is bluish.
To see a CIE diagram and look at the coordinates, go here:
http://www.yorku.ca/eye/ciediag1.htm
or here:
http://www.yorku.ca/eye/ciediag1.htm
or any of a number of Google-able sites.
This morning, I had planned to open a new thread, with the following question:
If the light from the sun contains all sorts of random wavelengths, then why does it appear yellow? And if the light has mostly yellow wavelengths, then why do white objects appear white instead of yellow?
But instead of just starting a new thread, I did a search and found this one. So I see from the previous posts that it is not at all clear what sort of light wavelengths reach us (here on the ground). So instead, I’ll phrase my question differently:
There are times – usually when the sun is close to the horizon – when its light is dim enough that we can look directly at it. At these times, it appears (to me) to be of a distinctly red color. Can I conclude from this that (at those times) the light which reaches us is of primarily red wavelengths? If so, then why (under those conditions) does a white object appear white? Why doesn’t it appear red? Where are the other wavelengths coming from?
Under those conditions white objects don’t appear white, they appear pink. The easiest way to demonstarte this is to either take a photograph of a white object for later viewing, or to simply look at a green object, which appears dark green or grey.
The reason you think white objects still appear white in a red sunset is because the human brain has an astounding ability to compensate for precisely those changes. The eyes may detect that the white object is red, but the brain processes that image and feed it into your conscious centres as white. It’s essentially a software filter. But take a photo of a sheet of paper under conditions of a red sunset, then go inside and look at it under electric light. You will be surpirsed to discover that it is in fact rose pink. That’s because the camera doesn’t have a software filter an simply produces an image of what is really there.
But do we all see colours the same?
I mean, the colour red to me might look like blue to you, even though you would have grown up calling it red. Or it might look like a colour you’ve never seen.
How would we ever know?
Why would this be? Seeing the sun as slightly yellow (or any other color) wouldn’t negatively impact a person’s ability to live long enough to reproduce. Seeing the sun as pure white wouldn’t give the person an evolutionary advantage.
Mutations are random. Only the counter-reproductive ones die out. Evolution is not purposeful.
The sun is really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really bright redyellowwhite.
Really?
[junior mod]You should have started a new thread and linked to this one for context, not resurrected a 2-year-old zombie.[/jm]
Thanks, sorry, I’ll keep it in mind for the future.
I did think of this, but I’m still skeptical. I was outside this morning at 6 AM, a very humid day, and it was very easy to look directly at the sun, which had a very distinctly salmon color to it. There may have been a slight salmon tinge to the white objects that I looked at, but if it was there at all, it was very very slight. Shouldn’t I expect the white objects to be just as colored as the sun itself? They sure seemed a lot paler than that.
But I must admit that I did not have my camera with me, and by the time I got home the sun was the usual very bright yellow-white. Maybe tomorrow…
Meanwhile, here’s a thought experiment we can try. Suppose we go to a planet that has a red sun and look around. What colors would we see? I would expect to see nothing blue or green or yellow. Everything would be a shade between bright red and dark red and black. Without artificial lighting, where would other wavelengths come from?
Some people claim that HID headlights are the color of natural sunlight, if true it’s blue-ish I suspect they were just sold a story however.
CalMeacham already answered your question.
IOW, the"other wavelengths" come from the light that gets scattered by the atmosphere. Most of that light still reaches the ground, but if you look up, it seems to be coming from the blue sky, not the yellow sun. In space, the sun would appear almost pure white.
Heh. Kinda surprised to be answering my own thread.
As for why an object can look a color other than red under a red light, look at these (eChalk: Optical illusions) optical illusions. Since everything around them is red, your brain concludes there is a red light, and changes the perception to try and figure out what the color actually is, and would look like under a white light.
The sun is yellowish-white. That’s the color they told us at the Harvard-Smithsonian Observatory semester course I took in astrophysics, that’s the color I’m sticking with.
Here’s why.
Cool stars have most of their light shining in the red end of the visible spectrum, so they look red. Slightly warmer stars shine orange, because most of their brightest light shines in that part of the spectrum. Interestingly though, they shine red light brighter than the red stars do. It’s just that the orange is even brighter. There’s also a decent amount of yellow light in the orange stars, as well.
Getting hotter, there are some yellow stars. These shine orange and red even brighter than the orange and red stars do, it’s just that the yellow is even brighter than that. There’s also green and blue light coming from them that the yellow overpowers as well.
The very brightest wavelengths of visible light from the sun are in the portion of the spectrum we see as green. However, the green part of the spectrum is very narrow, whereas the yellow part is very wide. So there’s a lot of yellow at a bunch of different wavelengths shining just about as bright as the green. But at this point, all the visible colors of the spectrum are shining pretty friggin bright, which means the light looks mostly white, but most of the very brightest light from the sun is yellow, so it’s white with a yellow tinge.
Stars a bit hotter than the sun shine a more pure white, even though one might expect that they’d look green or greenish blue. That is in fact the brightest light coming from them, but there’s so much bright light at all wavelengths at that point, they look white.
Hotter still, we get to bluish-white (stars hot enough to shine blue shine a LOT of blue light, and the amount of light in the rest of the spectrum coming from them overpowers their levels in cooler stars to a degree that it’s just not funny.)
There are stars even hotter than that, that are a more pure blue. These stars are shining crazy amounts of all frequencies of light, but the blue is just that much brighter.
So the sun doesn’t look a lot different in our sky than it looks from space, yellow-white. But isn’t the blue sky caused by scattered sunlight? Yes, but not so much from the sunlight shining directly down on us, but from the light shining toward spots on the earth where the sun appears to be on the horizon. The blue from the light shining in those directions gets scattered our way to make our blue sky in daylight, and those parts of the world that are experiencing sunset or sunrise get the light leftover, which heavily skews toward red and orange.
Now that is a cool piece of trivia!
Very good post. I do not understand this last paragraph though. Could you explain it slower? Especially this bit I don’t get: “the light shining toward spots on the earth where the sun appears to be on the horizon”
I think I can explain it.
If it is noon in San Francisco, it’s 8 pm in London. In London, the sun appears to be setting on the horizon. Because the light reaching London passes through the atmosphere at an oblique angle, the shorter rays scatter, making the sky in London appear red and orange. The blue rays spread out in the atmosphere, making the sky appear blue in Chicago. The light hitting Chicago directly doesn’t scatter; it only travels a short distance through the atmosphere, so we see the sun in nearly it’s true color. So the color of the sky at noon in Chicago doesn’t come from the light hitting the atmosphere above Chicago. It comes from the light hitting the atmosphere over London and being scattered.