Sunlight refraction at sunset at different latitudes?

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Discussion Overview

The discussion revolves around the refraction of sunlight at sunset and how it varies with latitude. Participants explore the implications of the Earth's curvature, the angle of incidence of sunlight, and the differing paths of sunlight at various latitudes, particularly comparing the equator to higher latitudes. The conversation includes technical reasoning and visualizations related to atmospheric paths and angles.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that sunlight refraction is greater at higher latitudes due to shallower angles of incidence, leading to longer atmospheric paths.
  • Others argue that the angle of incidence appears the same at different latitudes when considering corresponding angles in diagrams.
  • One participant emphasizes the importance of the Earth's curvature, noting that the path through the atmosphere is longer at higher latitudes.
  • There is a discussion about the visualization of angles of incidence, with questions about whether the angle is steeper at the equator compared to higher latitudes.
  • Some participants clarify that while the path of sunlight remains the same, the path of the Sun in the sky varies with latitude and season, affecting the perception of refraction.
  • Questions arise regarding the definition of the horizon and how it relates to angles of incidence, with some participants expressing uncertainty about the terminology used.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between latitude, angle of incidence, and sunlight refraction. There is no consensus on the best way to visualize these concepts or the implications of the Earth's curvature on refraction.

Contextual Notes

Participants highlight limitations in their understanding of the horizon's definition and the assumptions made in their reasoning about angles and refraction. The discussion reflects a range of interpretations and visualizations that may not align.

Mohsin03129
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“Sunlight due to refraction is greater in higher latitudes than at the equator because of shallower angles of incidence to horizon. It takes longer for Sun to go down half a degree at sunset at shallower angles.”

When I draw a diagram of sun rays incident towards the earth, the angle appears to be the same at the equator and say at 60 degrees latitude Due to corresponding angles.

Can someone explain this statement / what am I missing ?
 
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Did you take into account that the Earth is a ball? The path through the atmosphere is longer at high latitudes.
 
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mathman said:
Did you take into account that the Earth is a ball? The path through the atmosphere is longer at high latitudes.
I understand this. That sounds like a different reasoning than the “shallow angle “ one though?
 
Shallow angle leads to longer path through atmosphere.
 
mathman said:
Shallow angle leads to longer path through atmosphere.
mathman said:
Shallow angle leads to longer path through atmosphere.
thanks, what is the best way to visualise this angle of incidence?
Is it steeper at the equator?
 
Outside of the equatorial zone, it is generally steeper at the equator than at higher latitudes.
 
Path of sunlight is the same. Path of Sun in sky is different.
At the same latitude, the sunlight due to refraction varies due to season due to the path of Sun varying.
On equator, at equinox, Sun falls vertically from horizon to nadir, 90 degrees below horizon; at a solstice, it falls just 66 degrees below horizon. Sun on its way to travel from horizon to 90 degrees below in 6 hours spends less time between horizon and half a degree than Sun on its way from horizon to culminate 66 degrees below in 6 hours.
 
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The only way I see the angle shallowing is if I draw a sun with parallel rays hitting earth.
The angle made by the ray with the normal to a tangent at any n-s point on the Earth surface gets shallower with increasing latitude. But surely normal to a tangent isn’t the horizon!?

I am actually not sure about the definition of Horizon here.. I was imagining the horizon to lie on the East West latitude line and the angle of incidence shouldn't change with this horizon.
 
Parallel rays are what happens. the Earth's diameter is around 9000 miles, while the sun is around 93 million miles away.
 
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mathman said:
Parallel rays are what happens. the Earth's diameter is around 9000 miles, while the sun is around 93 million miles away.
Yes I know that
 
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snorkack said:
Path of sunlight is the same. Path of Sun in sky is different.
At the same latitude, the sunlight due to refraction varies due to season due to the path of Sun varying.
On equator, at equinox, Sun falls vertically from horizon to nadir, 90 degrees below horizon; at a solstice, it falls just 66 degrees below horizon. Sun on its way to travel from horizon to 90 degrees below in 6 hours spends less time between horizon and half a degree than Sun on its way from horizon to culminate 66 degrees below in 6 hours.
snorkack said:
Path of sunlight is the same. Path of Sun in sky is different.
At the same latitude, the sunlight due to refraction varies due to season due to the path of Sun varying.
On equator, at equinox, Sun falls vertically from horizon to nadir, 90 degrees below horizon; at a solstice, it falls just 66 degrees below horizon. Sun on its way to travel from horizon to 90 degrees below in 6 hours spends less time between horizon and half a degree than Sun on its way from horizon to culminate 66 degrees below in 6 hours.
Are you referring to the northern horizon here?
 
  • #12
Mohsin03129 said:
Are you referring to the northern horizon here?
A diagram of these angles would be useful
snorkack said:
Path of sunlight is the same. Path of Sun in sky is different.
At the same latitude, the sunlight due to refraction varies due to season due to the path of Sun varying.
On equator, at equinox, Sun falls vertically from horizon to nadir, 90 degrees below horizon; at a solstice, it falls just 66 degrees below horizon. Sun on its way to travel from horizon to 90 degrees below in 6 hours spends less time between horizon and half a degree than Sun on its way from horizon to culminate 66 degrees below in 6 hours.
when you say degrees below horizon , is that from the normal to a horizon?
 

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