How does the sun seem flattened at sunset?

How does the sun seem flattened at sunset?

Atmospheric refraction is responsible for the apparent flattening of the sun's disc during sunrise and dusk. Because the density and refractive index of the atmosphere diminish with altitude, rays above and below the sun on the horizon are refracted to varying degrees. As a result, the sun appears to flatten. The effect is most noticeable in clear, calm days when the sun is low on the horizon.

The sun appears slightly flattened at sunrise and sunset because the angle between its rays as they reach the earth's surface and the horizontal plane is less than 90 degrees. At other times of day, the sun is seen perfectly round because it is rising or setting beyond the horizon.

This article was written by NASA's Science Writer Kelly O'Brien. It originally appeared on

Why is the sun oval at sunset?

The sun is near the horizon during dawn and dusk. Light rays from the upper and lower sections of the sun's perimeter bend unequally when they travel through the earth's atmosphere. That is why, at sunrise and sunset, the sun appears round or flattened. The more rapidly it rises or sets, the more sharply defined its edges become.

The earth's atmosphere refracts (bends) light waves from the sun that reach it. This causes stars that are far away from us not to appear round but rather dim and fuzzy. The farther away a star is, the more warped (or bent) light waves it receives from the sun. The closer a star is, the less warped its light waves are by the atmosphere, so it appears brighter than those around it.

Atmospheric refraction causes all objects in the sky other than the moon and planets to look oval at twilight. The effect is most noticeable with high-magnitude stars such as Alpha Centauri (the nearest star system to Earth), which looks like a half-moon when viewed with the naked eye on a clear night with no clouds.

Stars appear round to someone looking up at them with unaided eyes because human vision is relatively insensitive to differences in distance between an object and the eye itself. However, telescopes reveal finer details about celestial objects than the unaided eye does.

Why does the sun look flattened near the horizon in Class 10?

In class 10 terrain, the angle at which sunlight strikes the ground is about 45 degrees. The light travels farther along the ground than upward into the sky, so most of it gets reflected back toward the sun. Only a small amount reaches the surface of the earth.

At noon, the sun is directly overhead. Because light waves spread out as they travel through air, water, and other materials, shadows are formed where there are no objects to block them. At midday, even though the sun is straight up above the horizon, all visible surfaces are still receiving direct illumination from all parts of its body. So there are no shadowed areas on the landscape at midday.

At night, objects that block light rays spread those rays out over a larger area. So even though the sun is only slightly below the horizon at night, its light falls on a much smaller fraction of the earth's surface than at midday. Most of it is reflected back into space.

This is why nights are darker than days are bright.

Why does the sun look elliptical in shape?

Light refraction by these layers can cause the sun to look flattened or distorted. Objects closer to the horizon are raised the most, and the sun's lower limb is raised more than the top, giving it an oval appearance. This is why sunset and sunrise tend to be flat shapes rather than round.

The earth also has an effect on the sun. As the earth travels around the sun, it blocks some of the sunlight reaching us during certain parts of its orbit. This is why we get seasons: The sun is not always at a equal distance from the earth, so some regions receive more sunlight than others at any given time. Seasons affect everything about our world that relies on plants producing energy through photosynthesis: Trees don't grow uniformly high and wide; plants with thicker stems tend to grow in warmer climates while those with thinner stems grow in colder climates. Animals that live off the land vary in size depending on which part of the world they're from; animals from cold climates are usually smaller because they need less energy per unit mass.

Finally, the sun itself affects how it looks to us. The farther away an object is, the less its apparent size is magnified when compared to distant objects. So even though the sun is actually a very large sphere, when viewed from far away it appears much flatter than if seen up close.

About Article Author

Martha Flock

Martha Flock has always been fascinated with how people are connected to each other through time, space, energy, love or light. After her own personal experiences in life-altering moments led her on a quest to discover more about herself and others in this realm of being human she decided to become an astrologer so that she could help others understand their own journey better.

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