# What would the horizon look like if the world were flat? **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [August 24, 2006, 12:19am UTC](https://boards.straightdope.com/t/what-would-the-horizon-look-like-if-the-world-were-flat/369970 "2006-08-24T00:19:37Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Toyman991](https://avatars.discourse-cdn.com/v4/letter/t/a9a28c/32.png) [@Toyman991](https://boards.straightdope.com/u/Toyman991)\ **Post date:** [August 24, 2006, 12:19am UTC](https://boards.straightdope.com/t/what-would-the-horizon-look-like-if-the-world-were-flat/369970/1 "2006-08-24T00:19:37Z")
A decade or so ago, my brother and I were sitting on a beach gazing at the horizon when he commented on its pronounced curvature. I then said that even if the wolrd were flat we might still perceive some curvature of the horizon since the horizon would still encircle us. In other words, if we could see for fifty miles, it would appear as though we were standing in the middle or a 100 mile wide disk. To this, he replied “hogwash” even though he could not describe how the horizon would appear in this hypothetical flat world. This question has bothered me ever since. So, how would the horizon appear in a perfectly flat world? John ---
**Author:** ![TimeWinder](https://avatars.discourse-cdn.com/v4/letter/t/bcef8e/32.png) [@TimeWinder](https://boards.straightdope.com/u/TimeWinder)\ **Post date:** [August 24, 2006, 1:01am UTC](https://boards.straightdope.com/t/what-would-the-horizon-look-like-if-the-world-were-flat/369970/2 "2006-08-24T01:01:14Z")
Assuming: 1. Rhe "flat"world is infinite (or at least farther than you can see) in each direction 2. There’s nothing in the way to block your vision (no buildings, etc.) 3. You’re limited in your vision by atmospheric occlusion, and 4. That occlusion isn’t something close by (like snow, fog, heavy rain, smoke, whatever). I.e. it’s “clear” out and you can see for hundreds of miles. …then you’re both right. You would, effectively be on a disk, because you could see the same amount in each direction. But the horizon would be a line, or so close to it that you wouldn’t be able to tell. Why? If the distance is great enough, you’re basically ON the disk (the displacement due to your height being negligible). Cut a circle out of paper, cut it in half, and hold it up to your eye if you don’t believe me. On “real” earth, the horizon appears curved because it falls away from us in all directions. You’re basically on a hill. On your flat one, it doesn’t. Now, if you (someone who grew up on a sphere) were placed on this earth, I suspect that your brain would overcompensate, and you’d have the perception of being in a vast bowl, similar to the way that flat monitors seem to be concave if you’re used to a curved one. Plus, you could see much, much farther than on earth, and the only corresponding experience here would be to be standing in a valley. ---
**Author:** ![Nava](https://avatars.discourse-cdn.com/v4/letter/n/da6949/32.png) [@Nava](https://boards.straightdope.com/u/Nava)\ **Post date:** [August 24, 2006, 8:54am UTC](https://boards.straightdope.com/t/what-would-the-horizon-look-like-if-the-world-were-flat/369970/3 "2006-08-24T08:54:47Z")
Full of mountains. At least around here. ---
**Author:** ![Dijon\_Warlock](https://avatars.discourse-cdn.com/v4/letter/d/a9a28c/32.png) [@Dijon\_Warlock](https://boards.straightdope.com/u/Dijon_Warlock)\ **Post date:** [August 24, 2006, 11:33am UTC](https://boards.straightdope.com/t/what-would-the-horizon-look-like-if-the-world-were-flat/369970/4 "2006-08-24T11:33:22Z")
This is probably more suited to GQ, because there’s probably a factual answer to the question. Nevertheless, I remember reading a few decades ago about an optical phenomenon while flying over the ocean (no mountains in sight, nor land rises of any kind: just “flat” water): if you fly low enough over the ocean, then while the horizon will be completely horizontal (there’s a coincidence, eh? ) all the way around your field of vision, it will actually appear to be above what is directly below you, so that you appear to be travelling in the interior of a shallow bowl. It may have been _OMNI_ or _Scientific American_ or something, and I don’t remotely remember their explanation. [sub]I guess it’s a good thing this _isn’t_ in GQ, huh?[/sub] On a humorous note, I remember a quip that the late, great guitarist Michael Hedges told about growing up in Enid, Oklahoma (paraphrasing): "I grew up in Oklahoma, in a town called Enid…which is mostly known to crossword puzzle solvers as a 4-letter name for a town in Oklahoma. "It’s really flat there. "I remember our family dog ran away once. “We watched him for three days…” 😃 ---
**Author:** ![Freddy\_the\_Pig](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@Freddy\_the\_Pig](https://boards.straightdope.com/u/Freddy_the_Pig)\ **Post date:** [August 24, 2006, 1:49pm UTC](https://boards.straightdope.com/t/what-would-the-horizon-look-like-if-the-world-were-flat/369970/5 "2006-08-24T13:49:26Z")
> [@Toyman991](#): > > A decade or so ago, my brother and I were sitting on a beach gazing at the > horizon when he commented on its pronounced curvature. I then said that > even if the world were flat we might still perceive some curvature of the > horizon since the horizon would still encircle us. In other words, if we > could see for fifty miles, it would appear as though we were standing in the > middle or a 100 mile wide disk. Of course it would. You’re exactly right, and your logic is correct. > [@](#): > > To this, he replied “hogwash” even though > he could not describe how the horizon would appear in this hypothetical flat > world. Your brother would never make it as a Doper. > [@](#): > > This question has bothered me ever since. So, how would the > horizon appear in a perfectly flat world? The difference in appearance between an infinite, flat Earth and our round, 25,000-mile circumference Earth would be close to nil. We did the math in GQ a while back; I’m too lazy to look it up but our sky stretches something like 180.07 degrees from horizon to horizon (from eye level) because of the curvature of the Earth. A flat Earth would stretch exactly 180 degrees. Imagine staring out at the ocean, with the horizon lifted _ever so slightly_ higher than it is right now. That would be the difference with a flat Earth. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [August 24, 2006, 2:07pm UTC](https://boards.straightdope.com/t/what-would-the-horizon-look-like-if-the-world-were-flat/369970/6 "2006-08-24T14:07:18Z")
> [@](#): > > Nevertheless, I remember reading a few decades ago about an optical phenomenon while flying over the ocean (no mountains in sight, nor land rises of any kind: just “flat” water): if you fly low enough over the ocean, then while the horizon will be completely horizontal (there’s a coincidence, eh? ) all the way around your field of vision, it will actually appear to be above what is directly below you, so that you appear to be travelling in the interior of a shallow bowl. Lots of people have remarked on this illusion, including, IIRC, Mark Twain.I think it’s in Poe’s “Hans Pfall” as well. The illusion comes from the perception that you’re clearly 'way up in the air (you can see the ground below you), but the horizon is apparently level with you (you’re not high enough for the curvature of the earth to have any noticeable effect), so it seems as if the horizon is on your level, while the ground is very far below. This makes a lot of people perceive the ground as being bowl-shaped (Twain was mountain-climbing, by the way. Pfall was in a balloon). Whatever. I’ve never experienced it. To me, the ground is like an infinite flat plane, and the horizon only _seems_ to be on a level with me because it’s effectively infinitely distant, and an infiniterly distant horizon splits sky and ground evenly. so on a true infinite plain, things would appear very much like they do on the real earth. The smidgen of extra land you can see would have vanishingly small effect. People who, when they’re up high in a plane or a mountain, will see the world as a curved bowl whether it’s a globe or an infinite flat plane. One arguable exception – if there’s a lot of gradient index in the air because of heating or other reasons, yiou can perceive the ground as a bowl because light rays through a gradient index (one that varies with height) can truly bend light rays, like in the case of a mirage. Hard-Core SF writer Hal Clement used this to good effect in his novel **Mission of Gravity** , where the Mesklinites, who live on an ultra-high gravity world, see the horizon _above_ them in a very real sense (they have to look _up_ to see it), becvause their intense gravity causes gravitational gradient index change in the air. So they can _see_ that they live in a bowl. They even have gone as far as to perform spherical trig on their map to prove that their world is a bowl. It isn’t, of course – it’s an ellipsoid. Their measurements have been accurate, but their science hadn’t advanced far enough to explain the optical efect, until an Earthman sets down on the pole (where the gravity is lowest() and persuades some to venture over the edge of the “bowl” (which would be like sailing “over the edge of the world” ) to help him out. Classic SF. ---
**Author:** ![Bricker](https://avatars.discourse-cdn.com/v4/letter/b/977dab/32.png) [@Bricker](https://boards.straightdope.com/u/Bricker)\ **Post date:** [August 24, 2006, 2:37pm UTC](https://boards.straightdope.com/t/what-would-the-horizon-look-like-if-the-world-were-flat/369970/7 "2006-08-24T14:37:37Z")
Speaking of classic SF – how would the horizon look on the Ringworld? Was Niven’s description on the money? I ask because I seem to remember that in Ringworld, people could SEE the Ring… but I always thought that the Ring was so thin in comparison to its length that if you were standing “on the ground” you’d simply see a flat horizon, not a curving upwards one.