# How can one prove that the earth is a sphere (or close to it)? **URL:** \ **Category:** Factual Questions\ **Created:** [October 15, 2018, 11:50am UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973 "2018-10-15T11:50:12Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [October 15, 2018, 3:19pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/21 "2018-10-15T15:19:47Z")
> [@Bullitt](#): > > That’s not a definitive proof. > **[The Ice Wall](https://wiki.tfes.org/The_Ice_Wall)** > > The Flat Earth Society primarily concerns itself with the known Earth - the area which the light from the sun affects. Along the edge of our local area exists a massive 150 foot Ice Wall. The 150 foot Ice Wall is on the coast of Antarctica. The Ice... The claim is that the ice wall is the “edge” of the known world, and that whatever is beyond it is unknown. > [@The Flat Earth Society Wiki](#): > > Beyond the 150 foot Ice Wall is anyone’s guess. How far the ice extends; how it terminates; and what exists beyond it, are questions to which no present human experience can reply. All we at present know is, that snow and hail, howling winds, and indescribable storms and hurricanes prevail; and that in every direction “human ingress is barred by unsealed escarpments of perpetual ice,” extending farther than eye or telescope can penetrate, and becoming lost in gloom and darkness. Some hold that the tundra of ice and snow stretches forever eternally. > . > . > . > Temperatures are thought to approach absolute zero the further one explores outwards. Exploration in this type of pitch black freezing environment is impossible for any man or machine. We live on a vast plane with an unknown diameter and an unknown depth. Dr. Samuel Birley Rowbotham held that knowing the true dimensions of the earth may be something that is forever unknowable by man. They don’t list an explanation for why a transantarctic flight can start at the coast on one one side of Antarctica and then arrive at the coast on the far side of the continent. This is something that should be impossible according to the flat earth model. To be fair, this isn’t a simple test available to us common folk. If you actually did it, your observations would be dismissed by any flat-earther who wasn’t on that flight with you. They’d cite some kind of navigational error, saying you actually flew on some kind of long arc that brought you back out to the coast somewhere else along the edge of the world. If you offered to take a flat-earther with you, they’d likely decline, since (according to their model) your flight would never return. On the off-chance you managed to convince one to come with you, they’d again cite navigational error as the reason for your safe return to the known world. An alternative: Circumnavigate Antarctica, hugging the coastline and measuring distance traveled. By the spherical-earth model, the distance should be about 8900 miles. By the flat-earth model, it should be more like 50,000 miles. They could claim some kind of speed/distance measurement error, but they’d have to explain why it would be so repeatable - by different planes/navigators/pilots. Eventually they’d have to fall back to their old standby, claiming a vast conspiracy theory. At which point you have to admit there’s nothing you can do. The kinds of people who believe in conspiracy theories are the kinds of people who can never be convinced of the truth of anything that casts doubt on their conspiracy theory - no matter how big and implausible the conspiracy theory may be. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [October 15, 2018, 4:25pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/22 "2018-10-15T16:25:37Z")
> [@Machine\_Elf](#): > > [The Ice Wall - The Flat Earth Wiki](https://wiki.tfes.org/The_Ice_Wall) > > The claim is that the ice wall is the “edge” of the known world, and that whatever is beyond it is unknown. It’s plenty known. Haven’t you read _At the Mountains of Madness ?_ ---
**Author:** ![Munch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/munch/32/5281_2.png) [@Munch](https://boards.straightdope.com/u/Munch)\ **Post date:** [October 15, 2018, 4:28pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/23 "2018-10-15T16:28:51Z")
> [@bizerta](#): > > OP here. When they interviewed some of these nuts, they also said that the moon landing was a hoax, so no one is on the moon to create the illusion of an eclipse “cycling”. How do these whack-a-doodles explain how we know, in advance, when a lunar eclipse will occur. No - some of them believe that the moon is semi-transparent, and cycles through various iterations of the moon phases. > [@Gorsnak](#): > > You might not have intended that pun, but it’s the best one ever. 😉 ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [October 15, 2018, 4:32pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/24 "2018-10-15T16:32:41Z")
[I refer Honorable Doper to the answer I gave when this question was posed almost six years ago](https://boards.straightdope.com/sdmb/showthread.php?t=679679): > [@](#): > > Originally Posted by Antonio Pigafetta, one of 18 first to circumnavigate the Earth > > “On Wednesday, the ninth of July [1522], we arrived at one of these islands named Santiago, where we immediately sent the boat ashore to obtain provisions. […] And we charged our men in the boat that, when they were ashore, they should ask what day it was. They were answered that to the Portuguese it was Thursday, at which they were much amazed, for to us it was Wednesday, and we knew not how we had fallen into error. For every day I, being always in health, had written down each day without any intermission. But, as we were told since, there had been no mistake, for we had always made our voyage westward and had returned to the same place of departure as the sun, wherefore the long voyage had brought the gain of twenty-four hours, as is clearly seen.” ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [October 15, 2018, 4:34pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/25 "2018-10-15T16:34:14Z")
People all over the globe believe that the earth is flat. GaryM ---
**Author:** ![Shoeless](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/shoeless/32/7099_2.png) [@Shoeless](https://boards.straightdope.com/u/Shoeless)\ **Post date:** [October 15, 2018, 4:50pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/26 "2018-10-15T16:50:20Z")
> [@Alpha\_Twit](#): > > No, according to Flat-Earth logic, that’s no more definitive than if you said that someone you know saw Sasquatch, Santa Claus and the little dog from the old Taco Bell commercials downing tequila shooters at last year’s cinco de mayo celebration. It’s an anecdote. What kind of physical, tangible proof can you show me that you personally have made that journey? Oh, you have none? Well then you’re just lying to support the conspiracy! By that logic, you could just as easily call bullshit on their Flat Earth theory. “Have you been to the edge? Have you seen it with your own eyes? Then you have no proof that the Earth is flat and you’re just lying to support the conspiracy!” ---
**Author:** ![DCnDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dcndc/32/2842_2.png) [@DCnDC](https://boards.straightdope.com/u/DCnDC)\ **Post date:** [October 15, 2018, 4:56pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/27 "2018-10-15T16:56:10Z")
> [@bizerta](#): > > Yesterday, on CBS Sunday Morning, they had a segment on flat-earthers. Are these people just ignorant or are they putting us on? I was always under the impression it was an attempt to shoehorn religion into science, or vice-versa. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [October 15, 2018, 5:45pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/28 "2018-10-15T17:45:42Z")
> [@bizerta](#): > > I was once on a cruise ship at sea on a pristine cloudless evening. As I stood on the deck, I watched the sun disappear below the horizon. As soon as the sun vanished, I ran up a flight to the next deck and witnessed the sun setting again about 10 seconds later. There are lots of way to demonstrate a spheroid Earth but this is not one of them. As the sun disappears past the edge of a flat Earth, naturally taking a higher vantage point would allow you to see the sun again. When a ship is sighted at the horizon, first the top of its mast is visible then gradually the lower parts of the ship become visible. If Earth were flat you would see the whole ship as soon as you could see any of it. ---
**Author:** ![Alpha\_Twit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alpha_twit/32/265_2.png) [@Alpha\_Twit](https://boards.straightdope.com/u/Alpha_Twit)\ **Post date:** [October 15, 2018, 6:01pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/29 "2018-10-15T18:01:50Z")
> [@Shoeless](#): > > By that logic, you could just as easily call bullshit on their Flat Earth theory. “Have you been to the edge? Have you seen it with your own eyes? Then you have no proof that the Earth is flat and you’re just lying to support the conspiracy!” Agreed, the problem is that they’re used to being called on their bull and are completely unfazed by it. They **know** , with absolute perfect clarity, what the Truth is. At best, anyone who disagrees with them is just simply mistaken. There is no amount of logic, facts, science, historical or photographic evidence or personal testimonial that can sway them from their world view. It’s useless to attempt to sway their views on this matter and I waste no time on the attempt. ---
**Author:** ![Munch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/munch/32/5281_2.png) [@Munch](https://boards.straightdope.com/u/Munch)\ **Post date:** [October 15, 2018, 6:09pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/30 "2018-10-15T18:09:42Z")
> [@Shoeless](#): > > By that logic, you could just as easily call bullshit on their Flat Earth theory. “Have you been to the edge? Have you seen it with your own eyes? Then you have no proof that the Earth is flat and you’re just lying to support the conspiracy!” That’s where they want to take the conversation. It’s all a conspiracy, and the “fact” that access to “Antarctica” is heavily regulated by international treaty is proof enough to all of them that the Rothschilds are all in control (or whatever). ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [October 15, 2018, 6:19pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/31 "2018-10-15T18:19:00Z")
I wonder how flat earthers explain the fact that the moon appears upside down when seen from Australia, compared to how it looks from the northern hemisphere. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 15, 2018, 7:58pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/32 "2018-10-15T19:58:23Z")
Hm, it sure was nice of the Rothschilds to let my mom (a retired elementary-school teacher) visit Antarctica a few years back, then. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [October 15, 2018, 8:35pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/33 "2018-10-15T20:35:53Z")
If you really want to know what they believe, the _Oh no, Ross and Carrie!_ podcast did interviews of [Mark Sargent](http://ohnopodcast.com/investigations/2017/11/30/ross-and-carrie-traverse-flat-earth-part-5-the-mark-sargent-interview) and [Jeran Campanella](http://ohnopodcast.com/investigations/2018/7/20/ross-and-carrie-traverse-flat-earth-part-7-the-jeran-campanella-interview). They also participated in some meetings and experiments with flat earthers - just search their [web site](http://ohnopodcast.com/) for “flat earth.” I think Mark Sargent seemed to imply that the sky is a giant artificial display that can show the stars, Moon, etc in any way they want us to see them. I remember Ross asking if it was like a lenticular display, showing different things depending on view angle, and he basically said yes. With this explanation they can dismiss pretty much any argument based on observing the sky. ---
**Author:** ![cormac262](https://avatars.discourse-cdn.com/v4/letter/c/f14d63/32.png) [@cormac262](https://boards.straightdope.com/u/cormac262)\ **Post date:** [October 15, 2018, 9:07pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/34 "2018-10-15T21:07:06Z")
My girlfriend’s brother works with a guy who is a flat-earther. So much so that his daughter caused a stir in school by confronting her teacher who was showing a spherical earth. This guy has been dying to “discuss” his view with me - with the challenge for me to prove him wrong. I’ve given this a lot of thought, and even checked out the flat earth website (there are SO many questions about that model, and you need to have some “basis” or foundation from which to start any counter-arguments). I decided two things: 1. that to prove that the earth is round might be “too much”. So I decided to focus on dis-proving the flat earth model. I figured if I could poke holes in his view, he would then be open to the truth and see how none of the failings are valid with the true model. 2. it would be best to dis-prove his view with observations that he could see/confirm personally. He would not have to trust anything other than his own experience. (no trusting those “faked” NASA photos, etc.) My first thought was “if the earth were flat, why would there be a need for time zones ?” That is, a flat earth would all experience the same “day” and “night”. But the flat-earthers have an explanation for that: the sun is a LOT closer than you think, and in being so close, the “daylight” is focused on only parts of the (flat) earth at a time. I considered the eclipse idea (with the flat earth model, it is unclear “what” causes lunar eclipses). But this would require having him observe a lunar eclipse, and this could take a while. So my next idea was kind of an inverse of Eratosthenes’ approach. Being that the flat-earther is in the northern hemisphere, I was going to have him measure the angle from the horizon to the North Star (I even made a crude sextant for him) at different locations (one where he lives, one several hundred miles south). IF he believed the North Star to be “far enough” away, then the angles (his latitude) would be different. This could not be with a flat earth. Again using the North Star, if I could get him to travel south of the equator, I was going to have him confirm that he could no longer see the North Star. But this was a bit trickier in that it might be tougher to find “reference stars” to “point to” the North Star (or where it should be) as well. I thought this might be too prone to error to be conclusive. ---
**Author:** ![jasg](https://avatars.discourse-cdn.com/v4/letter/j/f0a364/32.png) [@jasg](https://boards.straightdope.com/u/jasg)\ **Post date:** [October 15, 2018, 9:07pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/35 "2018-10-15T21:07:08Z")
> [@Alpha\_Twit](#): > > Lunar eclipses > > As the Earth passes between the Sun and Moon, it always produces a circular shadow. It’s not possible for a flat, disk like Earth to always produce such a shadow. Only a nearly spherical world can do that. You must have missed this eclipse [photo](https://imgur.com/a/476Dwc5) 😃 ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [October 15, 2018, 9:24pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/36 "2018-10-15T21:24:24Z")
> [@cormac262](#): > > 1. that to prove that the earth is round might be “too much”. So I decided to focus on dis-proving the flat earth model. I figured if I could poke holes in his view, he would then be open to the truth and see how none of the failings are valid with the true model. The problem with this approach is, disproving one flat-earth model does not prove a round/spherical earth. > [@](#): > > My first thought was “if the earth were flat, why would there be a need for time zones ?” That is, a flat earth would all experience the same “day” and “night”. But the flat-earthers have an explanation for that: the sun is a LOT closer than you think, and in being so close, the “daylight” is focused on only parts of the (flat) earth at a time. Yes, their model usually shows the sun hovering over the flat earth, [like this](https://www.quora.com/Where-specifically-does-the-flat-earth-model-fail). That link also discusses problems with this model, so that’s a good start. Major points being: how do they explain sunsets? And how do they explain why the Sun doesn’t get bigger mid-day? That last point is easy to measure. Just rig up a simple [pinhole projector](https://www.timeanddate.com/eclipse/box-pinhole-projector.html). > [@](#): > > IF he believed the North Star to be “far enough” away, then the angles (his latitude) would be different. This could not be with a flat earth. Wouldn’t work, they think the night sky is a dome above the flat earth. ---
**Author:** ![Alpha\_Twit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alpha_twit/32/265_2.png) [@Alpha\_Twit](https://boards.straightdope.com/u/Alpha_Twit)\ **Post date:** [October 15, 2018, 9:43pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/37 "2018-10-15T21:43:27Z")
> [@cormac262](#): > > This guy has been dying to “discuss” his view with me - with the challenge for me to prove him wrong. Your reply doesn’t need to go any farther than [Hitchens razor.](https://en.wikipedia.org/wiki/Hitchens%27s_razor) ---
**Author:** ![Iggins](https://avatars.discourse-cdn.com/v4/letter/i/b9e5f3/32.png) [@Iggins](https://boards.straightdope.com/u/Iggins)\ **Post date:** [October 15, 2018, 10:13pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/38 "2018-10-15T22:13:05Z")
Have there been any “prominent” flat-earthers that have renounced their views? Such a person could help explain the thought process both for believing and non-believing. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [October 15, 2018, 10:45pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/39 "2018-10-15T22:45:53Z")
> [@CookingWithGas](#): > > […] > > When a ship is sighted at the horizon, first the top of its mast is visible then gradually the lower parts of the ship become visible. If Earth were flat you would see the whole ship as soon as you could see any of it. I have heard this many times, but when I try to verify it, it never works. The horizon and distant objects are indistinct for too many reasons, such as haze. Have you actually tried this? I believe the earth is round, I just don’t think this demo works well enough to use. ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [October 16, 2018, 12:19am UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/40 "2018-10-16T00:19:05Z")
> [@Napier](#): > > I have heard this many times, but when I try to verify it, it never works. The horizon and distant objects are indistinct for too many reasons, such as haze. Have you actually tried this? > > I believe the earth is round, I just don’t think this demo works well enough to use. At 6’ the distance to the horizon is ~3 miles, which is pretty easy to demonstrate. [Previous page](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973.md?page=1) [Next page](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973.md?page=3)