Comment on The colour of the Sun is white
Spuddaccino@reddthat.com 8 months ago
It’s really a pale blue. If it were white, the visible spectrum would be pretty even, but you can see the graph is higher on the blue edge and lower on the red edge. There’s enough green and red to brighten it a lot, but it’s definitely blue.
In fact, the sun’s surface temperature is around 5800K, and you can look up what color that actually is wherever you go light bulb shopping.
This shows the colors based on temperature, and the sun is firmly in the “Day White.” It’s called white, but you can see it’s pretty clearly blue, especially next to the “Direct Sun” color.
NoRodent@lemmy.world 8 months ago
It’s more complicated than that. “White” is a completely made up term, it has no physical basis. Colors are a perception, they’re not physically real. We just gave labels to some frequencies of the electromagnetic spectrum and their different combinations. And just like a camera, the human brain uses white balance correction to compensate for the fact that in different times of the day, the sunlight reaching us here on Earth has different color temperature (because it travels through different thickness of atmosphere), and by extent to compensate for different color of artificial lighting. So what our brain perceives as “white” is much dependent on context. It’s how the infamous white+gold/blue+black dress illusion works like. It’s why when you put on ski goggles with orange lenses, the snow looks yellow at first but becomes “white” after a while. Then you take them off and the snow becomes momentarily blueish before it balances to white again. You can also force yourself to have the white balance temporarily out of sync in each eye.
If you printed out your chart and looked at it at different times of day or under different lighting conditions, what you think as neutral white would change too. So you can’t really say which white is the “true white”, it’s all relative.
Spuddaccino@reddthat.com 8 months ago
Colors are a perception, true, which is why we don’t really talk about colors, we talk about wavelengths and temperature. 5800K is not white (relatively equal amounts of all visible light wavelengths), it’s light blue (decent amounts of most visible light wavelengths, but a significant peak in the 450-500nm wavelength band, which looks blue to us). Lightbulbs use color temperature because filament and halogen lights generate light the same way the sun does: by getting hot, and how hot it is determines the light wavelengths emitted. That’s why I included the chart, it’s a good analogue.
If you look at the graph provided in the OP, you can see for yourself that there’s significantly more blue than anything else being emitted.
NoRodent@lemmy.world 8 months ago
Says who?
That’s the keypoint, relatively. You’re comparing black-body radiation temperatures but at no temperature is the spectrum constant across the frequencies which we call visible light. So which temperature you choose to call “white” is up to how you decide to define it. And because our eyes have different sensitivity for different frequencies, I doubt that even if you produced a perfectly constant spectrum of visible light, that you would perceive it the same as what you call white on the diagram. Not to mention such a light source could be harder to find than you might think.
If you don’t believe me, you can start on Wikipedia and from there go down the rabbit hole which colors and color perception are.
Interestingly, you can define what a perfectly white object is, with the caveat that what frequencies in what ratio actually hit your retina is again dependent on the light source.
Spuddaccino@reddthat.com 8 months ago
Says the diagram in the OP, the EM spectrum of a 5800K star, which clearly shows a peak within the visible spectrum in the blue band, and a significant (25% or so) drop off by the time it gets to the red band. Those aren’t relatively equal.
As near as I can tell, your entire argument is based on what a human being perceives to be “white”, and I’m not talking about perception at all, because it lies. Examples:
The sky looks blue. It’s not blue, and you can tell by looking anywhere that isn’t the sky in the daytime, because the air is the same everywhere.
Related: the sun looks yellow. The sun looks yellow for the same reason the sky looks blue.
When I close my eyes, I can’t see anything. That doesn’t mean everything is black or the same color as my eyelids.
Your own dress example, where different people would see different colors in the same dress.
You and I are arguing about two completely different things. You are talking about what color something looks to be, in terms of colloquial terms used to describe things people can see. I am talking about what color it is, in terms of temperature and wavelength, which are things people can measure.