# 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:** 14\ **Page:** 9
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [March 8, 2020, 12:33pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/161 "2020-03-08T12:33:48Z")
> [@ftg](#): > > Re: Flat Earther motives. A lot of it is religious. The Bible says the Earth is flat, so it’s flat. As previously noted, I don’t think there’s a high correlation between religious belief and flat-earthers. To be sure, some claim to find a basis for this theory in the bible, and they quote certain verses - but the support these provide is decidedly modest. Here’s a commonly cited one: > [@Isiah 11:12](#): > > He will raise a banner for the nations and gather the exiles of Israel; he will assemble the scattered people of Judah from the four quarters of the earth. ---
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [March 8, 2020, 1:37pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/162 "2020-03-08T13:37:39Z")
> [@Whack-a-Mole](#): > > You forgot to give them oxygen. > > And cold weather gear. Did we? ---
**Author:** ![Arkcon](https://avatars.discourse-cdn.com/v4/letter/a/96bed5/32.png) [@Arkcon](https://boards.straightdope.com/u/Arkcon)\ **Post date:** [March 8, 2020, 2:16pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/163 "2020-03-08T14:16:07Z")
> [@TokyoBayer](#): > > I grew up conservative Mormon and was a Young Earth Creationist, as was everyone I knew then, including my high school biology teacher. > > There simple was nothing you could have shown me to make me change my mind. > > Flat earthers will believe, all evidence aside. Yes. But … did you and your family and teachers know that the Earth was round? If so, then why? And how were you so sure? The answers are, to as much as is possible, the answer to the O.P. We’ve touched on it often in this thread, as to what this accomplishes for Flat-Earthers. But Flat-Earthers don’t really want to argue the each is flat and there’s a wall around the surface of the Earth. They’re just “asking questions” – they’re only trying to prove that what you know, isn’t the “last word.” Plenty of people – racists, holocaust deniers, deep state derpers like to say, “I’m not a …, I’m just asking questions.” They’re tying to win an argument with personality. Like Ficer67: said, with a little training, you can use surveying equipment measure the lay of the land. Without the knowledge of the Earth’s curvature, you can’t do long distance surveying to the accuracy needed for proper construction. You have to ignore the obvious to win at being a Flat-Earther. It is the purest form of In Real Life Troll. ---
**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:** [March 9, 2020, 11:29am UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/164 "2020-03-09T11:29:38Z")
> [@ftg](#): > > Another response to **Ficer67** : > > Tide tables. You can find tide tables online for all around the world. Note that there is nothing unusual regarding tides in the S. hemisphere vs. the N. hemisphere. > > All calculated based on the Moon and Sun’s relative positions in the sky and a round Earth. > > If these tables were “fake”, the locals would immediately notice that the tides and tables don’t match up. > > _Flat Earthers can’t explain any of this_, not even why there are two tides a day, let alone give equations. Something that Newton did over 300 years ago with less data, no computers and Math he had to invent himself. And yet flat Earthers can’t give a single equation for any of this. Here ya go: > **[Tides](https://wiki.tfes.org/Tides)** > > The Tides are the rise and fall of sea levels experienced on coastlines at different parts of the earth. Tides occur on the oceans and inland seas, while lakes and rivers often do not experience tidal effects. Despite the popular explanation of the... There’s a video on that page. Something to do with the complexity/pattern of local variations in tidal amplitude, and how it appears the tides are caused by tidal nodes. TL,DW: Flat-earthers can explain away any round-earth evidence you care to provide. Don’t bother arguing with them. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [March 9, 2020, 12:19pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/165 "2020-03-09T12:19:15Z")
> [@Machine\_Elf](#): > > Here ya go: > [Tides - The Flat Earth Wiki](https://wiki.tfes.org/Tides) > > There’s a video on that page. Something to do with the complexity/pattern of local variations in tidal amplitude, and how it appears the tides are caused by tidal nodes. > > TL,DW: Flat-earthers can explain away any round-earth evidence you care to provide. Don’t bother arguing with them. Note that the video is just some clueless guy who since he doesn’t understand something (the reasons in local variation of tidal range) and only looked at the “for dummies” explantion web pages automatically goes into “it’s all a lie” mode. He visited Hawaii and didn’t notice any tides. Therefore … ??? Anyway, here’s a [tide table](https://www.tide-forecast.com/locations/Hilo-Hilo-Bay-Hawaii/tides/latest) for Hilo. They have tides. His suggestions for explaining tides: sea life (seriously) and plate tectonics. Nevermind the motion of plates needed to move so much water would give the planet non-stop giga-quakes. All the seismometers in the world are in on the round Earth conspiracy, I guess. And of course nothing regarding the Sun/Moon correlation in tide timing and strength. So the plates are moving more when the Sun and Moon are aligned and less when they are not??? Again, no real explantion at all. No equations. Nothing but “I don’t understand, so it’s all false.” ---
**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:** [March 9, 2020, 2:40pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/166 "2020-03-09T14:40:20Z")
> [@ftg](#): > > Again, no real explantion at all. No equations. Nothing but “I don’t understand, so it’s all false.” I didn’t say it was a _good_ explanation. My point is that you’re never going to encounter a FE proponent who concedes to the weight of your evidence. If they were capable of concession, they would have stopped being FE proponents a long time ago. ---
**Author:** ![Jet\_Jaguar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jet_jaguar/32/3562_2.png) [@Jet\_Jaguar](https://boards.straightdope.com/u/Jet_Jaguar)\ **Post date:** [March 9, 2020, 4:43pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/167 "2020-03-09T16:43:35Z")
Nothing will convince a FE’er. On Netflix, there’s a documentary about the FE movement called “Behind the Curve”, and in that film they deny the results of their own experiments that don’t agree with their beliefs. A couple of examples: - One guy acquired a very precise, $20,000 laser gyro that he intended to use to prove that the Earth is stationary. The problem was that the gyro had a persistent, built-in 15-degree/hour drift, and he was never able to figure out a way to satisfactorily compensate for it. - A group of FE’ers devised a demonstration to prove the Earth is flat. They found an irrigation canal that was straight and about 3-4 miles long. In this canal they placed three upright boards, one at each end and one in the middle. The board at one end and in the middle had a hole in it at at fixed height (X) above the water. They shone a spotlight through the hole at the end and in the middle. (An earlier version of the test with a laser genuinely did fail when the beam had too much spread at the far end to get any kind of measurement.) If the Earth is flat, then the light through the holes will also hit the far board at X height above the water. If it were curved, then the light would land above that height. In the end, the light was so high that they had to climb a ladder and lift the board up to reach it. You can hear them talking about the results during the closing credits, and IIRC they concluded that reeds along the canal banks refracted the light upward. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [March 9, 2020, 5:14pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/168 "2020-03-09T17:14:39Z")
I mentioned the ring laser gyro that drifts 15-degrees an hour back in post 122. Last I heard they were trying to figure out what kind of metal to use to shield the box from some mysterious ray that makes it look like there’s a drift. So far steel, lead, and beryllium have all failed. I have on my Kindle the first year of _Astounding_ magazine starting January, 1930. Most of the science on those stories is better thought out than the flerthers’ is. ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [March 10, 2020, 4:52am UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/169 "2020-03-10T04:52:53Z")
I have measured the difference in vertical over distances numerous times, and in multiple locations, both optically, and with radar. The distance/change of angle were consistent for each and all of the locations. I did it myself. (With the assistance of the US Army with the radar, where the calibration was pretty much a standard daily exercise.) None of this alters the opinions of anyone who believes that earth is flat. What is learned from shared ignorance is not amenable to refutation by evidence. I must admit that for the last couple of decades I have refused to listen to any opinions of people who believe in the Flat Earth on any subject whatsoever. Not worth the time spent listening. ---
**Author:** ![typoink](https://avatars.discourse-cdn.com/v4/letter/t/ecb155/32.png) [@typoink](https://boards.straightdope.com/u/typoink)\ **Post date:** [March 10, 2020, 8:14pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/170 "2020-03-10T20:14:59Z")
> [@Xema](#): > > As previously noted, I don’t think there’s a high correlation between religious belief and flat-earthers. I’ve heard at least one major figure in the Flat Earth community acknowledge that almost all the Flat Earthers they know are also Christian (pretty sure it was Mark Sargent in an interview, but I can’t pull it currently). I don’t think it’s as simple as “Bible says flat, I believe it.” It’s more about susceptibility to “simple answers” and a general aversion to science and government. It’s a very particular mindset where, I think, these people just fall in love with the idea of getting to feel like they have special secret knowledge. Every proof against their belief only serves to strengthen it, because their belief isn’t REALLY based on evidence, it’s based on a desire to be special and reject the mainstream. ---
**Author:** ![RioRico](https://avatars.discourse-cdn.com/v4/letter/r/f04885/32.png) [@RioRico](https://boards.straightdope.com/u/RioRico)\ **Post date:** [March 10, 2020, 9:17pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/171 "2020-03-10T21:17:53Z")
> [@typoink](#): > > It’s a very particular mindset where, I think, these people just fall in love with the idea of getting to feel like they have special secret knowledge. Every proof against their belief only serves to strengthen it, because their belief isn’t REALLY based on evidence, it’s based on a desire to be special and reject the mainstream. They might be believers, or merely gamesters, toying with mainstream “sheeple”. Sure, their lives depend on round-earth technologies, but how many “normal” folk know shit about their home watershed, where their H2O comes from and goes to? Who cares where the pipes are, as long as they deliver the fresh and drain-away waste? A flat-watershed guy will present [Escher’s WATERFALL](https://en.wikipedia.org/wiki/Waterfall_(M._C._Escher)) as a working model. Totally bonkers but fun to play with, right? Hey, we’ve seen those Gravity Anomalies where water flows and wheels roll uphill. There’s one in San Francisco’s Golden Gate Park. See, the Earth isn’t just flat-ish, it’s inverted, probably hollow, with us inside. Books on the subject line many shelves. Flat Earth is only one of a cascade of pseudoscientific systems. They’re everywhere. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [March 10, 2020, 9:36pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/172 "2020-03-10T21:36:22Z")
> [@typoink](#): > > It’s a very particular mindset where, I think, these people just fall in love with the idea of getting to feel like they have special secret knowledge. Every proof against their belief only serves to strengthen it, because their belief isn’t REALLY based on evidence, it’s based on a desire to be special and reject the mainstream. [Here is the final scene](https://www.youtube.com/watch?v=EBtx1MDi5tY) (I think) from the Netflix documentary “Behind the Curve” where a flat earther performs an experiment and proves to himself the earth is round. We do not get to see how he felt about that the next day. ---
**Author:** ![typoink](https://avatars.discourse-cdn.com/v4/letter/t/ecb155/32.png) [@typoink](https://boards.straightdope.com/u/typoink)\ **Post date:** [March 10, 2020, 9:58pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/173 "2020-03-10T21:58:40Z")
> [@RioRico](#): > > Flat Earth is only one of a cascade of pseudoscientific systems. They’re everywhere. Most pseudoscientific theories mostly exist in books or in the minds of a small number of cranks. Flat Earth isn’t a small handful of easily dismissed simpletons or trolls anymore. There’s a lot more of them than seems plausible, and it’s spreading faster than I ever would have guessed. I’ve had my eye on them for a long while as an active skeptic, but I’ve started to see Flat Earth stuff coming from people within my actual social network. Perhaps there’s no real risk and it’s fine to just laugh and roll eyes and look away, but…I’m a bit worried. If that degree of anti-intellectualism is catching on, there are going to be actual consequences. I think it’s fair to say that foolish thoughts have always existed, but the fact that they’re getting more coordinated and unified (eg the VERY high crossover with antivaxxers) is worrying. ---
**Author:** ![crowmanyclouds](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crowmanyclouds/32/19884_2.png) [@crowmanyclouds](https://boards.straightdope.com/u/crowmanyclouds)\ **Post date:** [March 10, 2020, 11:11pm UTC](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973/174 "2020-03-10T23:11:02Z")
> [@Whack-a-Mole](#): > > {…} We do not get to see how he felt about that the next day. Jeran ‘Jeranism’ Campanella is as flat as ever. He, literally, can’t afford to not be. Pimping ‘flat Earth’ and various other conspiracy theories is his only ‘job’. CMC fnord! [Previous page](https://boards.straightdope.com/t/how-can-one-prove-that-the-earth-is-a-sphere-or-close-to-it/822973.md?page=8)