Why do we only see rainbow arcs from the ground?

From ground level, the Earth's horizon interrupts the lower half of the rainbow circle, making only the upper portion visible as an arc. The antisolar point, which is the center of the rainbow circle, sits below the horizon during most rainbow conditions. The rainbow circle continues below the horizon where we cannot see it.

Where can you see a full circular rainbow?

Full circular rainbows are visible from high elevations above water droplets or rain. Airplane passengers sometimes see circular rainbows around the aircraft's shadow on clouds. Mountain climbers, people in tall buildings, and observers near waterfalls with spray below them can see complete circular rainbows when sun position and viewing angles align properly.

Why is the rainbow always opposite the sun?

Rainbows form when sunlight reflects inside water droplets and exits at 42 degrees from the antisolar point, the spot directly opposite the sun from your position. This geometric relationship means rainbows always appear in the part of sky opposite the sun. Your shadow's head points toward the antisolar point, the center of the rainbow circle.

Does everyone see the same rainbow?

No, each person sees light reflecting from different water droplets because everyone has a unique viewing position and personal antisolar point. Two people standing side by side see slightly different rainbows created by light from different droplets. Rainbows are personal optical phenomena rather than physical objects with fixed locations.

Why can't you reach the end of a rainbow?

You cannot reach a rainbow because it is an optical phenomenon that moves as you move. The rainbow always maintains a 42 degree relationship to your personal antisolar point. As you walk toward where the rainbow appears to touch ground, the rainbow moves to maintain that geometric relationship. It has no physical location or measurable distance.

What causes double rainbows?

Double rainbows occur when sunlight reflects twice inside water droplets before exiting. Primary rainbows reflect once, appearing at 42 degrees. Secondary rainbows reflect twice, appearing at 51 degrees with reversed color order placing red inside and violet outside. Both are complete circles with the secondary circle surrounding the primary one.

Can moonlight create rainbows?

Yes, moonlight creates rainbows called moonbows or lunar rainbows. These appear white to human eyes because moonlight is too dim to activate our color receptors. However, long exposure photography reveals moonbows contain the same color spectrum as solar rainbows. Moonbows follow the same circular geometry and 42 degree formation angle.

Rainbows Are Always Full Circles, Not Arcs

Why we only see half of the rainbow from the ground

Rainbows are always complete circles, but from ground level we only see the upper half as an arc. From airplanes or high mountains, circular rainbows appear.

Key Facts

True Shape

Complete circle always

Ground View

Only upper half visible

Airplane View

Full circle visible

Formation Angle

42 degrees from antisolar point

Light Source

Always opposite the sun

Water Droplets

Act as prisms

Color Order

Red outside, violet inside

Double Rainbows

Reversed color order

Perfect Geometry

Cone of light rays

Observer Centered

Unique to each viewer

Distance

Cannot be measured

Viewing Conditions

Sun behind, rain ahead

Quick Stats

Attribute	Value
Rainbow Angle	42 degrees from antisolar point
Primary Rainbow Colors	7 main colors (ROYGBIV)
Secondary Rainbow Angle	51 degrees from antisolar point
Droplet Size Required	0.5 to 5 millimeters
Sunlight Refraction	Bends at specific angles
Complete Circle Visibility	From high elevations only
Internal Reflection	One for primary rainbow
Color Width	Each band covers 2 degrees
Moonbow Possibility	Lunar rainbows exist

About Rainbows Are Always Full Circles, Not Arcs

Rainbows are always complete circles, never just arcs. However, when viewed from ground level, the horizon blocks the lower half of the circle, creating the familiar arc shape.

How Rainbows Form

Rainbows occur when sunlight interacts with water droplets suspended in the atmosphere. Each droplet acts as a tiny prism that bends and separates white sunlight into its component colors. Red light bends least while violet bends most.

The Geometry of Circular Rainbows

Rainbows always form as circles because of the consistent geometric relationship between the sun, observer, and water droplets. Light exits water droplets at a concentrated angle of 42 degrees from the antisolar point, the spot directly opposite the sun from the observer's perspective. If you draw an imaginary line from the sun through your head to the antisolar point, then measure 42 degrees in any direction from that point, you trace a circle.

Why We Usually See Arcs

From ground level, the horizon interrupts the lower half of the rainbow circle, making only the upper portion visible as an arc. The antisolar point sits below the horizon during most rainbow viewing conditions. Your shadow's head marks the antisolar point.

Viewing Full Circular Rainbows

To see a complete circular rainbow, you need elevation above the rain and proper sun position. Airplane passengers sometimes observe circular rainbows around the aircraft's shadow projected on clouds. Mountain climbers occasionally see circular rainbows in mist below their position.

The Antisolar Point and Rainbow Position

The antisolar point is the center of every rainbow circle. This point always sits directly opposite the sun from your viewing position. If the sun is 30 degrees above the horizon behind you, the antisolar point is 30 degrees below the horizon in front of you.

Each Person Sees Their Own Rainbow

Rainbows are personal phenomena centered on each individual observer's antisolar point. This means everyone sees their own unique rainbow. You cannot walk to where a rainbow touches the ground because the rainbow moves as you move, always maintaining that 42 degree relationship to your personal antisolar point.

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Did You Know?

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Every rainbow is a complete circle, but the ground blocks the lower half from view

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Airplane passengers can sometimes see circular rainbows around the plane's shadow on clouds

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Each person sees their own unique rainbow from light reflecting off different water droplets

•

The center of every rainbow circle is the antisolar point, directly opposite the sun from you

•

You can never reach the end of a rainbow because it moves as you move to maintain 42 degree geometry

•

Double rainbows have reversed color order with red on the inside and violet on the outside

Frequently Asked Questions

Yes, rainbows are always complete circles, never arcs. From ground level, the horizon blocks the lower half, creating the familiar arc shape. From elevated positions like airplanes, mountains, or tall buildings, observers can see rainbows as full circular rings. The circular shape results from consistent 42 degree geometry between sun, observer, and water droplets.