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What Do Flat-Earthers Believe?  ................. Who cares?         
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Let's see, "Truth is Eternal" or St. Basil and St. Augustine's opinion on whether Scripture speaks of such things. I'll go with real Catholics on this one.

Notice that St. Augustine does not mention a heliocentric model? Yet there was still much discussion about this in his day.
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He thinks the discussion of shape is unimportant back then. Perhaps if he was in today's time, where the error of heliocentrism has led to total Godlessness, he might think it more important.

I'm sure if St. Augustine were alive today he would be much more concerned with actual errors rather than the shape of the Earth, which doesn't even fall within the realm of Salvific importance.

It is really something how you can read God's mind! WOW!

That's a tough question to answer!  I'd think of two things:  one the level and two perspective.  

All these people go out and use zoom lenses to look across a body of water and find that they can see all the way across a lake or far out into the ocean.   Of course, if the Earth was curved, then they shouldn't be able to see that far.  In regards to the level, the other thing was the shear drop of it.  Our Earth is supposed to have a diameter of about 8 thousand miles and a circuмference of about 25 thousand miles.  So, traveling from the North Pole to the Equator should be about 6 thousand miles and the traveler should experience a drop of about 4 thousand miles or a drop of 8 inches per foot traveled.  We of course experience no such thing!  It would be like living on a staircase!  Now I'm told that I shouldn't notice that, because I'm like an ant on a beach ball.  Well, I've traveled to the Equator.  Why didn't I fall off the ball?  I'm told that's because of Gravity.  O.k., if Gravity is real, then a 100 lbs of lead should attract more dust, then a newspaper.  However, in my experience, a newspaper attracts just as much dust as 100 lbs of lead or even 1000 lbs.  The idea that Gravity can hold a cruise ship to the carribbean, but I can easily walk around that ship seems fantastic (like fantasy).  

The second thing that really got me was Perspective.  It was pointed out to me that a telephone pole not far away looked like it was only a few inches tall.  Of course, the telephone pole handn't got any shorter;  it was just my perspective.  The telephone pole I stood next to still looked very tall!  So, Perspective created an illusion of roundness or curvature.  





 

What do you think the Bible means by "the firmament"?

Good question.

For some here, they seem to believe that we cannot say what it specifically means, because it's supposed to mean whatever anybody wants it to mean. It wouldn't be fair, for instance, to those who want to interpret it in a modernist, humanist manner. In other words, we can't attach a specific meaning, or it might hurt the feelings of those who don't agree. This is Vatican ll type of thinking. Don't be specific. Be ambiguous.

To Prove a flat earth theory to be fact?
HOLY BIBLE scripture is the single most compelling piece of evidence for God having created the flat earth.

https://www.cathinfo.com/the-earth-god-made-flat-earth-geocentrism/god's-flat-earth-in-scripture/

To me that's by far the weakest.  Scripture could easily be using various terms metaphorically or in non-scientific ways.

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All you have to do is step outside on a clear night and look at the full moon at midnight.
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But for flat-earthers, that's too much work.
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They'd rather read the Book of Enoch, SAY they're reading Scripture, but forget to mention that the Book of Enoch is not Scripture.
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Instead of looking at the full moon with their own eyes, they prefer to "believe" what is found in the Book of Enoch (not in Scripture).
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