SUN LIGHTS UP THE EARTH BUT THE SPACE IS DARK

This will be a little off-topic answer but you might find it interesting. Surely there are many responses saying that it’s not the light you see, those are some particles in the air that reflect the light to hit your eyes.

So here’s another question. Why does the sky look blue, clouds look white, sometimes the sky turns orange or even green and in direct sunlight things seem to be yellowish? Why does the sun look yellow in the first place? And after all, why do we call yellow/red to be warm and blue to be cold?

There’s very easy explanation for this. Different particles reflect different wavelengths. Usually in the air the “cold” blueish wavelengths are more reflected and the warmer ones go through without too much reflection. That’s because of the size and type of particles in the air. And this is exactly why the sky looks blue - it reflects more of “blue”. This also explains why the sun and direct sunlight looks yellow. If the blue was reflected, then remaining light is a bit yellow/reddish. The more air the light has to pass, the more yellow/red it becomes as it looses more and more blue shade. And that’s why in the evening or early morning the sky may appear red. The sun is so low, the light has to travel through a lot of air to reach you and it’s even more intense. On the other hand, water vapor is much better at reflecting light and that’s why clouds usually look white. Usually because if the sun is far away, the light reaching clouds will be reddish too and that’s why the whole sky will be lit red by the clouds.

So why do we call red to be warm and blue to be cold? Mostly because infrared is perceived as heat and it’s the closest thing to red wavelength, it follows the same pattern. If you are in direct sunlight, you will feel warm and the light will have warm color. If the sky is cloudy and you can’t see the sun, it will be colder and most of the light around will be the blueish light reflected from the atmosphere. That’s also what makes the sunlight so distinct and quite hard to replicate with a simple light bulb. Nice experiment to do is using thin water tank (1″ thick is enough) and filling it with soapy water. Ever noticed that soapy water looks blue? That’s the same effect! If you use white flashlight, the water will look blue but if you look at the light through the water, it will look a bit yellow. That’s how you can replicate the effect. This kind of tank with soapy water will reflect the blue color around the room but it will let the warmer colors to pass directly making the same effect as sunlight does. It’s a good hint for those, who like photography and would like to have something more natural. The whole effect is dispersing blue light around the room while keeping warm colors to be only direct from the light source.

And yes, using this trick you could see it in dark space as long as you have some light source. Looking at the image above (it’s higher to gain more attention) you can see, that the glass on the left side has yellowish tint to it but the whole liquid is blueish. The light source is just a regular, white LED.