Why the sky is blue

Human: Why is the sky blue?

AI: Ah, good question. To explain that I would need to explain the concept of the electromagnetic spectrum and quantum mechanics.

Human: Please do.

AI: Ok. The electromagnetic spectrum is a range of radiation that extends from very, very low frequency (far left on the curve) to very, very high frequency (far right on the curve). You can see it here, beginning on the far right with thermal radiation, and gradually tapering down as energy decreases as we move slowly along the x axis (increasing frequencies as we go from right to left). If we continue past UV and X-ray frequencies we come to gamma rays at the far left

Human: How does this relate to why the sky is blue?

AI: Excellent question. The sky is blue because of the way that we perceive visible light: part 1: color sensitivity: Humans and many animals can see shorter wavelengths of light than we can see longer wavelengths. We see violet and indigo, and we see long waves of red and orange much better than we see Yellow and green. Part 2: Brightness sensitivity : In bright conditions, it works better to have a higher retinal cone density in the central retina because it is exposed to much greater light intensity. In dim or dark conditions, it works better to have less cone density in the central retina and a greater density in the periphery which has a greater chance to detect a bit of light in a low-light environment.

Human: Tell me more

AI: One of the main human visual pigments is rhodopsin, a protein that is found in the retina. Rhodopsin is what is called a photopigment. A photopigment is a molecule that absorbs light. | The way that it works is that light travels into a cell in the back of your eye and is absorbed by a molecule in the rhodopsin, making it change shape. That changes a signal in a cell membrane in a chemical chain reaction, cutting off the chain if enough light is absorbed. Ultimately this results in altering the conductivity of the cell membrane, which operates neurotransmitters in your brain, causing your visual cortex to receive a signal. In other words, when light particles enter your pupil they hit the rhodopsin in the back of your eye, and this changes the shape of the molecule. This starts a chemical chain reaction that eventually sends a signal to your brain, telling it that you're seeing something.

Human: That's too complicated. Explain it like I'm five.

AI: Ok. The sky is blue because the Earth's atmosphere scatters sunlight in all directions and blue light is scattered more than other colors because it travels as shorter, smaller waves.

Human: Brilliant!

AI: Thanks!