squidy
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squidy asked in Science & MathematicsPhysics · 1 month ago

# What would the horizon of an ENDLESS flat earth look like?

Today I can see the nearest mountain, which is 100 miles away, but I can't see anything beyond it. But what if the earth were not a globe or even a disk, but a truly endless flat plane with the sun and outer space above it? I assume in good weather I would be able to see beyond the mountain, but for how far? And what if there were no atmosphere to obscure the view? The world would appear to almost curve upwards, into the sky forever. But I would obviously still be able to see the sky, it's not like it would touch at the top. Where would the horizon end? Would it depend on how tall or high up I am? What would I see when I look straight up? Science and math nerds please answer.

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• 1 month ago

If the sun were above, then the distant reaches of the plane would receive very little sunlight and be dark.

If there were no atmosphere (which would make the sky black) then the distant reaches of the plane would black.  The horizon wouldn't be sharp - it would be a region of grey gradually merging merging into black.

If there were atmosphere, light absorption and scattering would probably limit the range of what you see to 20 miles-ish and things would appear pretty much the same as what you see in real life on a clear day.

If there were very thin atmosphere, light absorption and scattering might limit the range of what you see to 1000s of  miles.  In this case you might see a dark line at the horizon - this would be the (poorly illuminated) distant reaches of the plane.

In my opinion.

• 1 month ago

That's a good question.  Think on this.  We can see the Sun, yet it's 93 million miles away.  So if the Sun were out there on your flat Earth you'd see it 93 million miles away...assuming there's nothing in its way.  But that's not very far.  Consider Sirius, the North Star.  It's 51,142,948,400,000 or 51 trillion miles away or more than 500,000 times farther than the Sun .  Yet we can see it with the naked eye.

Here's a bit of physics you might appreciate.  Light does not die out.  So once the light from the Sun or from Sirius is created and on it's way it'll keep on going forever or until something gets in its way.  That's why we can see a star trillions of miles away; that's why we could easily see it out that far on a flat Earth.