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Steve Baker, Blogger at LetsRunWithIt.com (2013-present)
Answered Jun 22, 2017
Well, to completely convince a flat-earther is almost impossible.
But to give you some suggestions, we really need to understand which “flavor” of flat-earthism your believer is infested with.
For example:
- Some believe that the sun moves around the ("flat") earth just as it does with the spherical earth.
- Some believe that the sun is a small object that moves around in a circular motion above the flat earth and casts light downwards in a beam like a flashlight.
The first group can be told to pick up the phone in the middle of the night - call someone in a time-zone far from yours - on opposite side of the world (the US embassy in Australia maybe) - and ask them “Is it dark outside?” - if it’s daylight where they are and it’s nighttime where you’re calling from - then the sun can’t be both above the flat plane for you and below the flat plane for them…so their idea of how things work is incorrect…which ought to convince them (but it won’t).
The second group are a little more sophisticated - and use the idea that the sun shines a circular beam of light onto the flat earth to allow that beam to light up one part of the earth and not the other. (How the sun would manage to shine on only a portion of the earth they can never explain.) However, in this version of events - there can be no sunsets. The sun has to be high enough in the sky to illuminate half of the land area at a time - so when daylight ends and night begins, you’d see the sun kinda fade out while still high in the sky - it couldn’t possibly descend to touch the horizon in the USA without setting fire to Europe!
This problem is defended by some flat-earthers by claiming that the laws of perspective are not what our modern physics tells us they are…so when the sun moves away from where you are, it’s light rays are distorted and it appears to be close to the horizon. They literally deny the evidence of our own eyes! IOW since the law of perspective gets in the way, they claim the problem is in the interpretation of the law itself. Kind of like the flat-earther Supreme Court of natural law.
If that’s their claim then why doesn’t the sun get smaller when it reaches the horizon - surely it must be further away now? (Some have ignorantly bought in to the fake depiction of a shrinking sun which is accomplished without the use of a solar filter, so as to deliberately overexpose the sun which gets less overexposed as it sets, thus appearing to get smaller, by fakery, illusion.)
But they’ll claim something bizarre like, “The suns rays are too strong for the sun to be shrunk down by perspective”. This is utter nonsense because either perspective works one way or the other - they can’t have it both ways. But now you’re into the weeds of geometry and physics - and you’re not going to win that debate.
Rather, you can point to the fact that the moon sets just like the sun does - and it’s light is nowhere near as bright as (say) a car headlight off in the distance…but again, you’re just not being convincing enough. Maybe moonlight has some special properties (they say) that prevent it from shrinking with perspective! (Whatever it takes to fake their "flat" earth is fair game, even if it is utter fantasy.)
The “proof” I like the best requires our flat-earther to take a plane ride and to look at the Moon. The orientation of the moon changes depending on whether you’re in the northern hemisphere - the southern hemisphere or on the equator. If you take note of how the patterns on the moon look in the Northern hemisphere - then in the South, they appear to be “upside down” - and at the equator, the patterns are rotated partway between the two. In a "flat" earth, the moon would have to be the same way up for everyone.
You don’t even have to pay careful attention to the patterns - you can just look at the shape of a “new moon” - it looks like a ‘(‘ in one hemisphere, a ‘)’ in the other and like a ‘U’ at the equator. Photos of the new moon in those three places might convince your flat-earther - but generally they’ll claim that photos that get in they way of their beliefs are “photoshopped”.
Another problem for flat-earthers is the stars. These look completely different on opposite sides of the world - but in a "flat" earth - they should all look pretty much the same. Why can people living in the North see the stars slowly rotating around “Polaris” - which is always in the North of the sky - when people in the South can’t see Polaris at all - and the stars appear to rotate IN THE OPPOSITE DIRECTION around an empty patch of sky.
Honestly - I’ve hung out on the "flat" earth forums - they have their beliefs SO firmly entrenched that NOTHING WHATEVER will convince them. They’ll shift their theories around - deny any and all evidence - fake their own evidence - make up new theories on the spot to cover any errors you find in their thinking - claim that NASA, the United Nations, all astronomers - are all in some gigantic conspiracy theory to hide the fact that the earth is really "flat" (why they’d do this is never fully explained!).
Once someone’s core belief is attacked, no amount of evidence, logic or reason will change their mind.