Eratosthenes’s Experiment Requires that the Sun's Light Rays that Reach the Earth are Parallel
But the Parallel Light of Spotlights Proves that the Light of the Sun is Not Parallel
When parallel light is shined onto an observer, this creates an effect like that of a spotlight. This is illustrated in the GIF below:
As can be observed with the above spotlight, when the light is shined directly at the viewer, the entire view is engulfed by bright light. The problem is that this is not what is observed with the sun.
Rather, the sun is visible as a circle in the sky, and yet, in the above spotlight GIF, when the spotlight shined on the observer, no circle of the light was visible at all, only pure bright light engulfed the entire view. And so if the sun's light were reaching the entire earth in parallel, then it should not appear as a circle in the sky, rather, then entire sky should be engulfed by light, just as what occurred in the spotlight experiment. But this does not occur.
Rather, the appearance of the sun is like that of a lamp, which does not have parallel light.
Since the light of the sun is like that of a lamp, which emits light in all directions, and is thus not parallel, then the famous experiment by Eratosthenes, which is often cited as proof that the earth is a globe, is based upon a false assumption that the light of the sun reaching the earth is parallel.
Instead, since the observed reality is that the light of the sun is not parallel, but like that of a lamp, it requires that the sun emits light in all directions (not parallel), and that the sun is closer (but still quite far) and that the earth is flat. This alternative would also produce different lengths of shadows when someone is at different locations on the earth. This is shown below:
And so by using observations that anyone can make and reproduce, the light of the sun has been proven to not be reaching the earth in parallel by comparing it to a known parallel light source (spotlights). This observation falsifies the assumption made in the Eratosthenes’s experiment, and thus falsifies that the earth is a globe. And because the light of the sun can be observed by anyone to behave like a lamp with light emitting in all directions, and not a spotlight with parallel light, the only model that suffices this condition is the flat earth model.