Why Is The Sky Blue? Our atmosphere scatters light in all directions; air molecules and gases contribute to this scattering process, with blue becoming more often visible due to how light is scattered in this way than any other color. C. V. Raman provides us with this explanation in his excellent book entitled Why Does the Sky Remain Blue.
The Sun’s Light
As sunlight reaches our atmosphere, it passes through gases and particles which scatter its light, altering its colors to create different shades. This explains why our skies appear blue: usually blue wavelengths scatter more than red ones; but other factors may affect its hue such as water vapor levels or pollution – on clear days with lower pollution levels the sky may show deeper shades of blue.
Sunlight contains seven colors that combine into what’s known as the VIBGYOR spectrum, an imaginary rainbow-like spectrum. When sunlight enters Earth’s atmosphere, however, it appears white due to air molecules scattering blue and violet wavelengths more than red wavelengths – this phenomenon is called Rayleigh scattering.
Due to shorter wavelengths than red light waves, blue and violet light scatter more easily; thus causing the sky to appear blue during daytime while at night it shows as an area dotted with stars.
Interesting enough, other planets also exhibit blue skies due to different atmospheric compositions than Earth. Mars for instance has much thinner atmospheric layers which scatter light less easily while its surface contains dust particles which absorb or reflect light back onto itself.
The color of the sky on the Moon differs slightly, too. Due to being made up of water molecules, its surface reflects more blue and violet wavelengths than any other colors; as a result, its appearance on its surface appears lighter blue than on Earth.
The blue color of the sky is determined by interactions among its elements – atmosphere, Sun’s radiation and visual system. There is no one-size-fits-all answer for why our skies appear blue – typically this result of sunlight scattering off particles in our atmosphere and scattered by gases such as nitrogen oxide.
The Earth’s Atmosphere
The Earth is enveloped by a relatively thin atmosphere. More commonly referred to as “air”, its components include mostly nitrogen (78 percent) and oxygen (21%), along with smaller concentrations of gases such as argon (0.9 percent), carbon dioxide (0.0395 percent; steadily increasing), water vapor, dust particles pollen grains, plant grains and other solid particles that reflect light from the sun, giving our skies their characteristic blue hue.
The troposphere is the lowest layer of our atmosphere. It stretches from the surface up to 9-17 km altitude depending on latitude. This layer accounts for 75% of its mass and hosts most weather systems and most clouds; additionally it is where most aeroplanes fly.
As air rises in the troposphere, it becomes colder and drier until reaching the stratosphere at approximately 50 km altitude. At this altitude, sunlight passes through layers of water vapor in the atmosphere to be colored blue by its filtering effects and eventually reaching Earth.
C. V. Raman was renowned scientist and Nobel Prize recipient who loved teaching children about science. This book created by two creative minds captures his enthusiasm for our world through anecdotes, milestone timelines and an explanation of The Raman Effect – encouraging readers to look up to the sky and contemplate its wonders!
The Sun’s Radiation
The sun emits electromagnetic radiation across its entire electromagnetic spectrum, including UV (ultraviolet), visible and infrared (IR). When sunlight reaches Earth’s atmosphere it is broken down into its component wavelengths and absorbed, producing colors primarily in blue, violet and red regions of the spectrum; any remaining radiation reflected from Earth surfaces gives our sky its signature hues.
The color of the sky depends on how much solar energy the Earth receives and how quickly its radiation travels through its atmosphere, along with inclination of Earth’s hemisphere towards the sun and other meteorological factors. Spring and summer, when tilted more toward sun, show bluer skies due to higher UV production by our Sun during these seasons.
Once sunlight enters Earth’s atmosphere, it begins to scatter and diffuse due to gas molecules in the atmosphere as well as minute dust particles – this process is known as Rayleigh scattering and it causes skies to appear blue during daylight hours and redder during sunrise and sunset.
Solar radiation sensors allow us to assess the sun’s radiance with precision. Essentially, these sensors measure sunlight intensity over a specific area and convert this data into “solar irradiance,” or the amount of power per unit area received from its radiation at various wavelengths.
This book is dedicated to Dr C V Raman, who lived his life to serve humanity with excellence. His passion was in sharing its wonders and speaking to children; we have endeavored to capture his spirit here by using photographs taken by the author as well as anecdotes and milestones to encapsulate the essence of this remarkable man’s spirit.
The Moon’s Radiation
Moon radiation reaches Earth as blue light. The color comes from similar processes to those that cause solar flares; however, here it’s the Earth’s atmosphere which scatters it and gives it its signature hue. As light travels further into its atmosphere and collides with gas molecules it loses more energy as energy is dissipated in colliding collisions, making its radiation less blue over time.
Blue light is created through the combination of wavelengths. This spectrum makes up what we perceive as the sky color; furthermore, as Moon’s light travels through Earth’s atmosphere it interacts with gases and particulates which alter its hue over time, giving a hint of other colors in its path.
Rayleigh scattering and ozone absorption combine to give the sky its blue hue. Rayleigh scattering occurs when light particles in an atmosphere bounce around, absorb radiation from collisions with air molecules, then emit it back again through Rayleigh scattering re-emit. This process works best at shorter wavelengths which represent blue colors of visible spectrum light.
Other atmospheric processes also contribute to the appearance of the sky. Haze can make it appear yellow, orange or red; dust can give it a dark grey tint; clouds may take different forms depending on their formation;
The color of the sky depends on how much light and heat is coming from the Sun, with brighter skies on days with more direct sunrays becoming bluer while darker and greyer hues develop when temperatures cool off significantly. This phenomenon occurs because more of the Sun’s radiation is directed directly at warmer temperatures while less direct rays come through at cooler temperatures.