The expanded explanation is that the spotlight changes shape throughout the year due to refraction and the varrying height of the sun throughout the year.
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Fact: Cold air is denser than warm air, and has therefore a greater refractive index.1
Fact: The sun is higher over the earth in its Northern Annulus and closer to the earth during its Southern Annulus.2
During Equinox the sun is positioned over the equator, the majority of its warmth spread over the ring of the equator. The sun is at it's middle point between hemispheres. The atmosphere in this area around the equator is at its highest temperature and therefore, since warm air has less of a refractive index than cold air, light can progress further through the atmosphere without bending towards the ground. This results in the spotlight of the sun conforming to the shape of the hottest areas. The end result gives the spotlight of the sun an oval shape taking up roughly one half of the earth:
When the Sun is over the North and at its highest altitude the spotlight is small and circular. This is because the sun is far from the earth and not heating the atmosphere up very much. At this time the entire Southern Hemisphere is in its Winter, and since cold air is denser than warm air, the refractive index is higher and light cannot proceed without being redirected into the earth. Since the earth is colder, the light is restricted to a smaller circle where summer exists in the North.
When the sun is over the South and close to the earth the sun is heating up the Southern Hemisphere, giving the spotlight a wide crescent shape. The shape is a crescent because when the sun is over the South it is winter in the North and the sun's light cannot penetrate the density of the Northern Hemisphere's winter.
Well, that actually made sense somehow... cold air has a higher refractive index than hot air, so the spot is not a perfect circle, it's a bit squeezed because the air is colder in the north and far south.
Except that the refractive index for air is around 1.00027 at 20°C (and 1 atm) and 1.00030 at -10°C (and 1 atm). That's a difference of less than 0.003% and yet you expect to believe that it's enough to transform the shape of the spot from a perfect circle to the oval represented in your picture?
But even then, let's say that it is the case. I'm still wondering why you would present such a picture and pretend that it accurately represents daylight during some time of the year.
Let's consider Australia. At latitude 30° south, Australia gets between a bit more than 10h and 14h of daylight, depending on the time of the year (winter solstice and summer solstice respectively). Yet, if I follow the 30° S latitude up to the spot in your picture, I count only 9h. It doesn't fit reality.
In fact, if you had to produce a spot that accurately represents the length of the day during the solstice of June, you'd get the spot in yellow (or something close to that) in the first attachment.
And in the second attachment, I drew the spot for the solstice of December (in red).
You're trying to tell me that the sun spot changes so drastically, only because of the 0.003% difference in the air refractive index change?
It's as I said on this thread or another one: to make FE theory work, you need magic. A magic sun or maybe a magic atmosphere. Probably both...