Scalene triangle would be a 2d view of a 3d phenomenon , is that correct?
To be honest I was looking for the egg shape image and landed on the scalene triangle and that felt thats good enough. And of course once I'd posted that I discovered the half egg image!
You know how it goes.
I know from looking at an infrared light on a shipyard security camera setup that infrared light is invisible to us. I saw the lamp and its red light as red but saw nothing of the infrared light itself or the things it was pointing at and illuminating.
It was only when looking at the screen attached to the camera did I see what was being illuminated by the infrared.
Therrefore to my mind visible red light such as we see at sunrise and sunset fades into infrared at sunset and merges into orange/ yellow etc at sunrise.
An artifact of our eyes presentation of the physical is the horizon line which is in the exact horizontal middle of our vision. The picture delivered is presented on a curved screen if you will that brings what's above the horizon and below it together at the horizon line.
We know they don't actually meet.
When we use our vision to look at a lighthouse from distance if the light is shining along the horizon line we see it illuminate the sea which our eyes make the water rise up between us and the lighthouse.
Above the water in the water vapour we call air the light appears to form an angle from source rising up until it vanishes as its limit is reached. This angle does not repeat on the seas surface because the sea is lower than the source and our vision is aligned to the level horizon so it 'sees' solid objects like the surface of the sea differently to lit water vapour.
I reckon all light is is a source being bounced off of water vapour. When there is a huge source as in the suns case we are unaware of the extent of the distance the sun illuminates as we cannot see the dsrkness where there is still water vapour but no light. Except we do actually know its limited as the blue sky shows us. And at night we get to see more as the blue fades out and anything lit by the setting sun is orange to red.
As this lighthouse light moves on through ninety degrees to point directly at us we see a bright centre with a ring of bright light diminishing in brightness the further it is from the source all of which appears circular. Only at the very edge of this circle of brightness do we get a glimpse of red light but its definitely there.
When the light points 180 degrees from our position we see no light because we are behind the source.
As it comes and goes from our vision its too weak a light so we do not see the red light at its edge.
The idea of the half egg shaped light from the sun comes from the slow morning quick night observable reality. Unlike the lighthouse example where the source has a back to it the sun appears to be omnidirectional.
Of course the possibility is there that it too has a back but it tilts about an axis as it travels over bus and never presents its back so we don't get to see it at any point during the day.
It is difficult if not impossible for our vision to show us the true limit of light and the shape it makes in the darkness.
Its also possible it turns enough to reveal its back once its gone beyond our visual limit.
If we use a torch in the dark that can can be focussed then it appears the light is circular from source to extremity which we can see be moving the toirch closer to and further away from a flat surface. Shine it at a ball and it is also circular in appearance. But shining it at a ball or a square so it is fully illuminated and then going round the opposite side of the ball or square we see the light actually illuminating much more than the surface.
This brightness overspill, to use a term (probably badly!), appears to be circular until the angle of the torch to the lit object is changed. We then see an egg shaped area of brightness around the object.
That's a very long winded way of showing you where I feel the half egg shaped pool of the suns light comes from. Its focussed and angled to do one thing very well, bring forth life at the edge boundary of liquid water and water vapour. That's what we are and where we are.
Sunset basically means the distance the light source, the sun, is from the edge of its light is much less than at sunrise. We see this in the way the light that lands on objets changes colour.
