The issue with this video being definitive is that you have the confounding factor of glare. Notice that when the sun gets closer to the horizon in the video, it not only gets relatively smaller, but it also changes shape (becomes more uniformly round), and also gets a lot more sharp-edged. When it appears to get "bigger" higher in the sky, this increased diameter may not represent the true apparent increase in diameter, but the glare of the sun's light on the camera lens or other components of the optical equipment, as well as glare from clouds, dust etc. This creates a diffuse "fringe" of light around the sun, making it look bigger than it actually is.

When the sun is lower in the sky, the argument would be it is shining through the atmosphere etc. edge-on, which filters the light, eliminates the glare, and produces the correct diameter, while if it is higher in the sky, the glare masks the true diameter and gives the impression of increasing size as it gets away from the horizon.

It is easy to replicate this effect: simply place a bright flashlight on something stable, take a few steps away, and try to take a cellphone photo of the light directly head-on. The resulting bright white, diffuse patch of light with soft edges doesn't reflect the true size of the flashlight bulb/reflector, but rather the glare of the intense light on the lens of the camera. If you dim the light (place tissue paper or translucent plastic over the flashlight's bulb end), the glare is decreased, and now you can see the flashlight's true smaller diameter.

However, there is a simple way to definitively prove whether the sun decreases in size or not as it rises or sets: a telescope fitted with a solar filter. This cuts out the glare and just shows the "disc" of the sun. It wouldn't even need to be a big or expensive telescope; just one with a safe solar filter. You could photograph it at the same magnification throughout the day and see if it changes in size.  In fact, the classic simple "pinhole" projection box method might even work; you could measure the diameter of the sun along the projected background with a ruler and see if it changes during different times of the day.

 Is anyone aware of someone using this method (solar telescope or projector) and measuring if the sun's objective diameter increases or decreases with its position in the sky?

With all due respect Ladislaus, I've looked at many videos online of this apparent increase and decrease of the sun's size, and I have never encountered any that use a true solar filter. There are many different filters that can be fitted to cameras/telescopes etc., but only a solar filter will actually cancel out the glare and provide an objective image of the sun's edge and surface. In a filter like this, the background will be completely black, and the sun will be white, bluish, or light yellowish.

Yes, the difference in size in the video is extreme, but as that simpe flashlight experiment above shows, glare can produce a dramatically larger appearance to a bright object in some circuмstances. Image A in the image I posted (where the light is uncovered) is significantly larger than the true size of the flashlight, all due to glare.  I honestly don't see why a solar filter would be considered "nonsense" if it is removing that bias of the glare and more correctly showing the size of something. 

Just to be completely clear, I'm not being confrontational here; I'm just legitimately interested in this and am asking everyone if it's ever been done that way before. Have you encountered any videos where a true solar filter was used and docuмented docuмented the change in size of the sun?

If the sun is overhead, you're actually looking through less atmosphere between you and the sun.  When it's lower on the horizon, there's much more atmosphere.  By the time you get to 30,000 feet or so, about 7+ miles, the atmosphere is very thin.  But if you look toward the horizon, the sun his hundreds of miles away and you're looking at it through lots more atmosphere.  If there's any humidity in said atmosphere, it's going to magnify the sun, to about the same size, regardless of the distance.  Rob Skiba did some experiments that demonstrate this, where his depiction of the sun reduced in size as it move away from the camera.  But he interposed a lens between the camera and "the sun" and it didn't change at all in size as it moved backwards (and also appeared to set).  Moisture/humidity magnify objects.



It's no accident that some of the best video of shrinking sun was taken across a desert.

This is also why the moon can look gigantic when it's low over the horizon.

I suggest that those who promote FE conduct their own experiments instead of relying on YouTube videos ...

If you will recall, last year I went to a lake and conducted an experiment using two different telescopes demonstrating that I couldn’t see an object that would be visible 20 miles away if the Earth was indeed flat. It was ignored and excuses were made.

Well, yes, but I'm not sure that Plato, Socrates or Aristotle would ever be considered as heretics for any reason since they lived long before the existence of the Catholic Church.

I don't know much about Plato or Socrates, but from what we know about Aristotle, through St. Thomas, he was of course a keen and astute observer of human nature and the natural word. But observing human nature is different than observing the shape of the earth. Other humans are in close proximity, and the shape of the earth is not. We are just little specks compared to the size of the earth. The only way to try to observe the shape of the earth in the days of Aristotle was through direct observation and mathematical calculations. It was easier to be mistaken back in his day, and there still aren't really good ways to try to observe the shape of the earth in our time. We can really only find evidence. Just my opinion.