Why Does Refraction Cause an Elliptical Sun?

In summary, the Sun appears elliptical during sunrise and sunset due to the bending of rays from its lower edge being more pronounced than those from its upper edge. This is caused by the refraction of light through the Earth's atmosphere, which acts as a lens. The effect is more noticeable when the Sun is near the horizon and decreases as its elevation increases.
  • #1
Pranav Jha
141
1
Why does sun appear elliptical during sunset and sunrise?

I have read that when the Sun (or Moon) is near the horizon, the rays from the lower edge are bent more than the rays from the upper edge. This produces a shortening of the vertical diameter, causing the Sun to appear elliptical
BUT i don't understand why the rays from lower edge are more bent due to refraction.
 
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  • #2
There is a lensing effect of atmosphere that makes this effect really noticeable, but even if you forget that, just think of atmosphere as a layer of glass. When you watch Sun near horizon, the light from top edge hits Earth near the place where you are standing more straight on than light from bottom edge. And by laws of refraction, the light that meets surface at greater angle from perpendicular is refracted more. Look up Snell's Law.
 
  • #3
The effect falls off sharply with increased elevation. The rays from the top of the Sun are going through less atmosphere than are the rays from the bottom of the Sun.
 

1. Why does refraction cause the sun to appear elliptical?

Refraction is the bending of light as it passes through different mediums. This bending is caused by the change in speed of light as it travels from one medium to another. When the sun's light enters the Earth's atmosphere, it passes through layers of air with varying densities. This causes the light to bend at different angles, creating the appearance of an elliptical shape rather than a perfect circle.

2. Why is the sun's elliptical shape more noticeable during sunrise and sunset?

During sunrise and sunset, the sun's light has to pass through a larger portion of the Earth's atmosphere before reaching our eyes. This means that the light is bent at a greater angle, making the elliptical shape more noticeable to us. As the sun rises higher in the sky, the light has to pass through less atmosphere and therefore appears less elliptical.

3. Does the Earth's atmosphere affect the degree of refraction and the sun's elliptical shape?

Yes, the Earth's atmosphere plays a critical role in the degree of refraction and the sun's elliptical shape. The Earth's atmosphere is made up of different layers of air with varying densities, and each layer has a different refractive index. This means that as the sun's light passes through these layers, it is bent at different angles, causing the elliptical shape to appear.

4. Can other celestial bodies also appear elliptical due to refraction?

Yes, any celestial body whose light passes through a medium with varying densities can appear elliptical due to refraction. This includes the moon, stars, and other planets. However, the degree of ellipticity may vary depending on the composition and density of the medium the light passes through.

5. Is refraction the only factor that causes the sun's elliptical shape?

No, refraction is not the only factor that contributes to the sun's elliptical shape. Other factors such as atmospheric turbulence, scattering of light by particles in the atmosphere, and the curvature of the Earth's surface can also play a role. These factors can further distort the sun's shape, making it appear more elliptical than it actually is.

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