Rainbows can sometimes form a complete circle from an airplane because the height at which the observer is situated influences the perception of the rainbow. From an airplane, with a bird's-eye view of the water droplets, the rainbow may appear to form a complete circle.
From the ground, one usually sees only a rainbow arc because our view is blocked by the horizon, the ground, or buildings. On the other hand, from an airplane, you are at a height, and your line of sight is not obstructed. As a result, you can observe more than just a simple arc, sometimes even seeing a perfectly round complete circle. This aerial position provides an extended viewing angle and instantly reveals the true hidden circular shape of this optical phenomenon.
From an airplane, the position of the sun matters a lot. To see a full-circle rainbow, the sun must be rather low on the horizon and located directly behind you. If the sun is too high, its angle no longer allows for the appearance of the entire circle, reducing the visible arc. In short, the closer the sun is to the horizon behind you, the better your chances of clearly observing the complete circular rainbow.
When the sunlight enters a droplet of water, it changes direction: this is refraction. The light ray bounces off the back surface of the droplet, a phenomenon called reflection, and then exits from the front, undergoing refraction again. During this journey, the white light from the sun separates into several different colors, each having its own specific angle of exit. It is this precise interplay of reflection and refraction within countless droplets that gives rise to the rainbow, revealing its colorful and perfectly circular side when viewed from an airplane.
To clearly observe a complete rainbow from an airplane, it often requires fairly precise weather conditions: a combination of sunshine, rain, and clouds. Typically, this occurs after or during a light shower, with fine droplets floating in the air just below the plane. There needs to be partial or scattered cloud cover, allowing sunlight to pass freely through certain gaps. Too thick clouds or intense precipitation limit visibility and disrupt the effect. The key factor is the presence of a homogeneous layer of suspended water droplets below the observer. If the conditions come together, then it is just what is needed for a bright and colorful spectacle.
A rainbow is actually always circular, even if from the ground we only see half of it. At altitude, your high position allows you to better observe this phenomenon: you can clearly see the water droplets arranged all around you, not just those located above the horizon. Each droplet reflects sunlight at a specific angle of about 42 degrees, forming a series of concentric circles. From the ground, the horizon hides the lower half of this circle, while in an airplane, with no obstacles in front of your eyes, the complete circular shape becomes perfectly visible. Simply put, it's just a matter of perspective and visual obstacles that show you it was all about a circle from the very beginning.
It is impossible to physically approach a rainbow: it is an optical phenomenon related to perspective and the internal reflection of light in water droplets, which causes it to "recede" as you move forward.
Did you know that there are moonbows, known as 'lunar arcs'? These rare optical phenomena occur when rays reflected by the Moon pass through very fine water droplets.
The similar phenomenon known as 'glory' or 'Brocken spectre' is a complete luminous circle surrounding the shadow of an aircraft or a person observing from a summit, caused by the diffraction of light through the small droplets present in clouds or fog.
For a rainbow to become visible, the sunlight must hit the raindrops at a very specific angle, usually around 42 degrees.
No, each observer actually sees their own rainbow, as this optical phenomenon depends on the exact position of the observer in relation to the water droplets and the sun. Thus, two passengers located in different spots on the plane perceive slightly different rainbows.
The unchanging order of colors in the rainbow results from the physical laws of light refraction in water droplets. The wavelengths of colors are refracted at slightly different angles, always creating the same sequence: red, orange, yellow, green, blue, indigo, and violet.
Sure! Here’s the translation: "No, even though airplanes offer an excellent perspective, it is sometimes possible to observe a complete circle from high places like mountains or very tall structures, if the weather conditions and the orientation of the sun are favorable."
To maximize your chances of observing a circular rainbow, choose a window seat located opposite the sun, meaning on the side opposite to its position in the sky.
It is almost impossible to observe a complete circle when you are on the ground, as the Earth's horizon blocks the lower half. However, from a high altitude, such as in an airplane, the lack of obstruction allows for a full circle to be seen.
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