Children tend to be naturally inquisitive, and one of their more frequent inquiries about why the sky is blue can often be answered with this simple fact: light scatters more strongly into blue wavelengths than other colors (red, orange, yellow, green, indigo and violet).
But why does that occur, and why does the sky look different on other planets?
The Sun’s Light
As sunlight passes through Earth’s atmosphere it is scattered into all directions by gas molecules comprising our planet’s air – this phenomenon is called Rayleigh scattering and it causes blue light to be scattered more than other colors; hence why the sky appears blue.
Blue has the greatest dispersal and shorter wavelength than other colors such as red. When white sunlight passes through our atmosphere it scatters more blue rays than red rays – hence why the sky appears bluer during daylight hours.
At night, when the Sun has set below the horizon and its light has to travel further through our atmosphere, its wavelengths become scattered more easily and therefore don’t make their way directly into our eyes as easily. This causes darkness in the skies.
An experiment to demonstrate this effect can be carried out simply. Add one drop of soap or milk to a full glass of water. When viewed from a distance, this mixture appears blue but changes color when looked upon directly due to shorter blue wavelengths scattering more readily than long red ones.
This science experiment is just one of many home or school science experiments available for kids (and adults!) to increase their knowledge of their environment. From curious preschoolers at home, to inquisitive students in class, kids often ask a variety of questions about nature – especially why certain things exist as they do. Understanding some basic principles about light, atmosphere and eye sensitivity can help kids (and their grownups!) answer various queries about nature posed by young minds – including these frequently asked queries about sky and nature from children! Here are our favorites:
The Earth’s Atmosphere
The sky is blue because Earth’s atmosphere reflects light differently depending on its wavelengths. While sunlight emits all colors of the rainbow spectrum, when reaching our atmosphere it dissipates into different wavelengths; those associated with blue spectrum colors become separated out and our eyes perceive this hue to be predominant – leading us to perceive the sky as blue.
Sunlight travels relatively straight through the atmosphere, but when it hits molecules of air molecules it gets scattered – this process is known as Rayleigh scattering after English physicist Lord Rayleigh who developed a mathematical formula in 1871 to describe it. Lord Rayleigh’s model showed that scattered light intensity varies directly with wavelength (i.e. shorter wavelengths scatter more). As blue and violet wavelengths have shorter wavelengths they scatter more.
When sunlight hits the atmosphere, it rebounds off air molecules to form reflections which scatter back in all directions – this effect being most dramatic near the horizon due to more interactions with sunbeams at close range, leading to multiple scatters occurring at one time or another – this causes sky colors to lighten gradually as one moves further from it. This phenomenon explains why its color gradually fades as you get further from it.
Open water’s signature blue hue is created through interaction of light with water molecules; longer wavelengths such as reds and oranges are absorbed into the ocean floor, leaving only blue light rays to reflect off its surface.
The Earth’s atmosphere also plays a significant role in shaping sunsets and sunrises by absorbing and scattering sunlight in different ways, giving some sunsets a distinctive orange hue while others become redder in hue. A beautiful orange sunset may have its source in forest fires or volcanic eruptions while reddish sunrises could be due to pollution or excess water vapor in the atmosphere – both causes can be tackled using cleaner energy sources and decreasing environmental footprints.
The Sun’s Radiation
When looking at the sky, what you see is actually a combination of various colors resulting from sunlight passing through atmospheric molecules. Blue light dominates, with other hues appearing less frequently – hence why the sky appears blue.
As sunlight passes through our atmosphere, it gets scattered by gases and dust particles in the air. This scattering effect is especially visible for blue wavelengths due to their shorter wavelengths than other colors of light; when light is scattered this way it travels further before arriving at our eyes; creating an overall blue hue which represents all of these scattered wavelengths.
Scientists did not gain a firm grasp of why our skies are blue until late in the 19th century, when Tyndall proposed that small particles of smoke contributed to creating its color. Although his explanation proved false, its effect is still present today.
Our skies appear blue due to molecules in the atmosphere that scatter blue wavelengths more strongly than red ones when exposed to sunlight, making our skies appear that way. When white sunlight hits our atmosphere, more blue components than red components get scattered, giving our sky its characteristic hue.
Have you noticed how the sky appears brighter blue higher overhead and fades out near the horizon? This is due to more atmosphere getting in its way when light travels overhead than nearer the horizon, leading it to get scattered more and be dissipated more.
Attributing our perception of blue skies to multiple factors can be challenging. First, our eyes are most sensitive to blue light from the Sun’s radiation; secondly, various chemicals in our atmosphere such as sulfur dioxide and nitrogen also contribute to their color; these emitted from factories or power plants increase how much blue light we see.
The Human Eye
As light travels through the atmosphere, it becomes scattered and bent in many different ways. Blue wavelengths tend to be scattered more readily than red ones, leading to blue light becoming the dominant form of illumination reaching our eyes – hence why the sky seems bluer.
However, it’s important to keep in mind that sunlight still contains all of the colors of the rainbow (red, orange, yellow, green, indigo and violet) mixed together – it just appears white due to reflection from surrounding objects like leaves – our brains interpret this light as white!
Our eyes contain special cells called cones which respond to various wavelengths of light, with red cones responding to low levels of scattered red light; green cones to low levels of scattered green light; and blue cones reacting strongly to blue wavelength scattering – giving rise to sky’s characteristic hue.
Without atmosphere, light would reach our eyes directly and appear white. In reality, however, sky is not actually blue – the hue depends on how much atmospheric pressure there is present: when there’s plenty of atmosphere present, its light appears more blue while less of it causes its hue to become more red.
atmospheric haze scatters blue wavelengths more than red and orange ones, leading to more diffuse blues being scattered than red and orange wavelengths. This phenomenon causes dawn or dusk skies to appear slightly redder because sunlight has had more time to travel through the atmosphere at these times of day than at other points during its journey through space.
Are you curious about the nature of blue skies? Check out this blog article from Tappity’s Curious Kids series, where children submit questions that are answered by experts at Tappity. Or submit your own query here!