As sunlight enters Earth’s atmosphere, its light is scattered by oxygen and nitrogen molecules present. Shorter blue wavelengths tend to be scattered more than longer red ones resulting in the sky taking on its signature hue.
At dawn and dusk, sunlight must travel further before reaching our eyes; more blue wavelengths scatter into the atmosphere leaving orange and red hues behind.
Rayleigh scattering
Day after day, sunlight scatters through our atmosphere as it passes through molecules and other small particles, and this phenomenon is commonly known as Rayleigh scattering after its discoverer: an English physicist by that name. Polarized light travels through the atmosphere in one direction and hits air particles with different orientations in various ways, creating scattered light of various intensities depending on particle size and wavelength; intensity is usually proportional to fourth power of wavelength for sufficiently small particles; thus violet and blue wavelengths scatter more intensely than longer red ones.
Why does the sky appear blue during the day? Because short wavelengths of Sun’s light are dispersed more strongly by atmospheric nitrogen molecules while longer wavelengths are absorbed by ocean and lake waters – this results in most of its energy reaching Earth as white light with only occasional streaks of blue or violet light appearing on its surface.
As the Sun passes lower in the sky, its light has to pass through more atmosphere, scattering itself more widely. As this occurs, blue light becomes less dominant as more reds and yellows reach our eyes directly – creating the look of Carolina blue skies at sunrise and sunset.
The hue of the sky depends on how our eyes’ cones respond to scattered light. Red and green cones tend to respond less strongly to blue than orange or yellow wavelengths, giving the sky its characteristic deep green color with only subtle shades of blue visible at times. Meanwhile, blue and violet cones respond much more strongly when exposed to scattered blue compared with orange or yellow lights, creating the appearance of mostly blue skies at night since more blue light from the Sun’s spectrum is scattered out into space than during daylight hours.
Dust and pollutants
As sunlight passes through Earth’s atmosphere, it interacts with gases and dust particles present. This interaction scatters light in all directions – with blue wavelengths being more widely scattered than other colors – thus giving our sky its distinctive blue hue.
As we gaze upward, our eyes take in all the colors in the spectrum; however, blue wavelengths stand out more because their shorter wavelengths make up more of the light that hits our eyes, and therefore more blue hues than other hues appear in the sky. Other wavelengths such as red are scattered less intensively and thus appear less in the sky than expected; nevertheless they do sometimes reach us and cause it to appear green or yellow!
Many believe that the color of the sky comes from dust and pollution in the air; this assumption, however, is false – in actuality Rayleigh scattering is responsible for creating its unique hue.
Light from the sun enters our atmosphere where it interacts with nitrogen and oxygen molecules in the air, which are smaller than the wavelength of light and thus adept at scattering its path – with blue light being particularly susceptible to being scattered by these tiny particles, making up most of what we perceive in terms of color.
At day, the sky appears blue; at night when skies are clear however, its colour transforms from blue to red or orange due to light traveling further through the atmosphere and coming into contact with more nitrogen molecules.
This explains why oceans and seas appear blue, as water molecules absorb longer wavelengths of red and orange light. You can conduct an easy experiment to demonstrate this; all it requires is a white torch and an imitation tank of water (or something comparable). When shining your light through it, watch as its hue shifts from blue to red as the light passes through it.
Sunrise and sunset
At nighttime, light travels further through the atmosphere than during the daytime, making it more likely that it reaches you directly. This explains why the sky appears blue: because blue wavelengths scatter less easily than violet ones and therefore comprise a greater portion of what we perceive; on the contrary, violet ones take up less of our visual field altogether.
At sunrise and sunset, light must travel farther through the atmosphere and therefore is more likely to be scattered by molecules in the air, like nitrogen and oxygen, that are smaller than wavelengths of blue light and can more easily scatter it. As a result, our eyes cannot receive direct light, and begins taking on a reddish hue as its direct path becomes obscured by air molecules like these which diffuse it instead.
At sunrise and sunset you may have witnessed something known as a green flash; this occurs when sunlight reaches the layer of atmosphere closest to Earth where bulk attenuation filters out all other colors except green through bulk attenuation; temperatures and composition within this layer allow this event to occur.
At home, you can perform an experiment that illustrates this effect for yourself. All it requires is a white light source, paper and something to simulate airborne dust or particles such as Dettol! Light the paper and shine it at the light source to show how different colors scatter – blue and violet light reflecting more strongly while red and orange reflect less. Compare your results to how the sky appears at sunrise and sunset; most vibrant overhead while becoming increasingly pale at the horizon due to scattering effects.
The sun
The Sun is an immense collection of gases, providing our solar system with light and heat. At its center lies a hot and pressurised state known as plasma that contains enough energy to sustain nuclear fusion and release tremendous amounts of energy that create the electromagnetic spectrum we witness on Earth.
As sunlight enters the atmosphere, it collides with air molecules composed of mostly oxygen and nitrogen atoms that are smaller than visible light wavelengths, scattering blue wavelengths more strongly than any other colors – creating what we perceive to be blue skies during daylight hours.
As you shine a beam of white light through a tank of clear water, it will appear reddened due to tiny particles such as dust or pollen in the liquid (Rayleigh scattering works similarly on a larger scale). Sunrise and sunset when more Sun travels through atmosphere to reach our eyes cause even greater Rayleigh scattering so shorter blue wavelengths get diverted, leaving yellows and reds free access into our eyes.
The Sun itself is white, yet it radiates many colours ranging from reds and oranges due to being classified as a yellow-dwarf star – meaning its heat level doesn’t quite meet requirements to burn hydrogen and produce heavier elements such as gold or silver.
The outer layers of our Sun are known as the chromosphere and corona, and can sometimes be observed during total solar eclipses. Their appearance differs dramatically from that of its photosphere: with the former emitting a warm white glow while corona acts like a crown-shaped structure. As for why one side is warmer than the other is still unknown; some researchers speculate that magnetic forces might heat it like when boiling over a burner on a stove – though further research needs to be conducted into how exactly this happens and from where this heating emanates.