# What is the point to flat earth? **URL:** \ **Category:** Factual Questions\ **Created:** [May 31, 2017, 12:57am UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748 "2017-05-31T00:57:18Z")\ **Posts on this page:** 20\ **Page:** 4
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [June 1, 2017, 8:26pm UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/61 "2017-06-01T20:26:55Z")
> [@Weisshund](#): > > I just thought of a test where the flat earthers can prove themselves beyond shadow of doubt. > (prove themselves wrong) … if we fix a laser to a verifiably leveled platform on the shore.… The laser beam, if the earth is flat, should be found the same average distance above the water at 30 miles, 50 miles, 90 miles, 300 miles, 1000 miles.… This is slightly problematic. A laser beam will _not_ traverse a perfectly straight line, for the same reason that the sun remains visible for some while after it is below the horizon: air is refractive and will bend the beam downward. Not quite to match the curve of the Earth, but enough that it will not match the raw measurement. ---
**Author:** ![Bones\_Daley](https://avatars.discourse-cdn.com/v4/letter/b/bc8723/32.png) [@Bones\_Daley](https://boards.straightdope.com/u/Bones_Daley)\ **Post date:** [June 1, 2017, 8:44pm UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/62 "2017-06-01T20:44:01Z")
> [@eschereal](#): > > , for the same reason that the sun remains visible for some while after it is below the horizon: If the sun is visible, then AFAIAC , by definition, it is above the horizon. ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [June 1, 2017, 9:06pm UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/63 "2017-06-01T21:06:56Z")
> [@Weisshund](#): > > I just thought of a test where the flat earthers can prove themselves beyond shadow of doubt. > (prove themselves wrong) > > Water is inherently flat and level. > The ocean is naturally a flat level place. You can use the levelness of water in a simpler way. Build a large pool, in a rectangular shape. Make sure the sides are absolutely straight - then fill it with water. You’ll find that water drains off the short sides, because of the curvature of the Earth, if the pool is large enough. For that matter, try to create anything that is both straight (measured by laser) and level throughout (measured by spirit level) - at some point, these requirements will conflict. ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [June 1, 2017, 9:21pm UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/64 "2017-06-01T21:21:55Z")
> [@eschereal](#): > > This is slightly problematic. A laser beam will _not_ traverse a perfectly straight line, for the same reason that the sun remains visible for some while after it is below the horizon: air is refractive and will bend the beam downward. Not quite to match the curve of the Earth, but enough that it will not match the raw measurement. In certain atmospheric conditions, the refraction can be increased. I’ve seen flat earth essays where they found a picture of a far-away city that you can see above the horizon, due to refraction. It’s probably a cold Lake Michigan and very still air in the morning, but the flat earthers don’t seem to comprehend that light can be refracted by air. ETA: A good example [here](http://www.abc57.com/news/mirage-of-chicago-skyline-seen-from-michigan-shoreline). ---
**Author:** ![Bones\_Daley](https://avatars.discourse-cdn.com/v4/letter/b/bc8723/32.png) [@Bones\_Daley](https://boards.straightdope.com/u/Bones_Daley)\ **Post date:** [June 1, 2017, 9:28pm UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/65 "2017-06-01T21:28:41Z")
> [@CurtC](#): > > In certain atmospheric conditions, the refraction can be increased. I’ve seen flat earth essays where they found a picture of a far-away city that you can see above the horizon, due to refraction. It’s probably a cold Lake Michigan and very still air in the morning, but the flat earthers don’t seem to comprehend that light can be refracted by air. > > ETA: A good example [here](http://www.abc57.com/news/mirage-of-chicago-skyline-seen-from-michigan-shoreline). The atmospheric refraction only applies to objects which are on the surface of the Earth. It is meaningless to talk of the Sun being “below the horizon yet still visible”. ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [June 1, 2017, 9:32pm UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/66 "2017-06-01T21:32:59Z")
> [@Bones\_Daley](#): > > The atmospheric refraction only applies to objects which are on the surface of the Earth. > > It is meaningless to talk of the Sun being “below the horizon yet still visible”. Bullshit. If the earth had no atmosphere, the position of the sun would be “below” (obscured by) the horizon earlier than it is with atmospheric refraction (which is also what reddens sunset/sunrise). ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [June 1, 2017, 10:06pm UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/67 "2017-06-01T22:06:53Z")
> [@watchwolf49](#): > > But at 42,000 feet, we can see further than 42,000 feet … I’m not saying it’s easy to see the curvature of the Earth from altitude … but I believe we can … > > Not sure what the “round table” analogy means … put our eye at table level and the table top looks flat … like the Earth … My point is that it’s hard to discern the curve from so close to the surface. Imagine a giant spherical water tank or something, 40 feet in diameter. The plane is then half an inch off the surface, to scale. The round table analogy is meant to show that the horizon itself is flat, the same as the rim of a table is flat. (Of course, the ground between you and the horizon isn’t flat, so a better analogy would be a slightly domed circular table.) You’re not seeing the curvature of the Earth, you’re seeing the curve of the “rim”, which will look more curved the more you look “down” on it. ---
**Author:** ![bonzer](https://avatars.discourse-cdn.com/v4/letter/b/45deac/32.png) [@bonzer](https://boards.straightdope.com/u/bonzer)\ **Post date:** [June 1, 2017, 10:42pm UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/68 "2017-06-01T22:42:06Z")
> [@Bones\_Daley](#): > > Good luck finding a portable laser beam that will stay parallel and visible over 1000 miles. > > There is a far easier experiment which could be carried out, if anybody felt the necessity to do so, which doesn’t involve farting around with laser beams. > > Over a measured straight mile, you erect 3 posts, one at each end and one in the middle. > > Using a mile long water level, you mark the level on all three posts. At each datum you tap in a nail. Using a surveyor’s theodolite, or even a pair of binoculars, you ascertain if all three nails are in the same horizontal plane. If they are, then the earth is proved flat. If the center nail is higher , then the earth is round. > > If my memory serves me right, the center nail should measure something like three inches higher than the two end nails. Though this sort of experiment is actually rather hard to do in practice. It’s essentially the [Bedford Level controversy](https://en.wikipedia.org/wiki/Bedford_Level_experiment) that so bedevilled Alfred Russel Wallace in the 19th century. The experimental complications give the deniers lots of quibble room, at least in their own minds. ---
**Author:** ![Bones\_Daley](https://avatars.discourse-cdn.com/v4/letter/b/bc8723/32.png) [@Bones\_Daley](https://boards.straightdope.com/u/Bones_Daley)\ **Post date:** [June 1, 2017, 11:07pm UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/69 "2017-06-01T23:07:39Z")
> [@bonzer](#): > > Though this sort of experiment is actually rather hard to do in practice. It’s essentially the [Bedford Level controversy](https://en.wikipedia.org/wiki/Bedford_Level_experiment) that so bedevilled Alfred Russel Wallace in the 19th century. The experimental complications give the deniers lots of quibble room, at least in their own minds. Similar in concept, agreed, but what I am suggesting would involve far fewer variables than in the Bedford Level experiment…Occam’s razor would be the watchword . A mile long water level would be difficult in practical terms, but the same result could be achieved with a shorter, more manageable level, and increasing the number of posts accordingly. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [June 2, 2017, 4:18am UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/70 "2017-06-02T04:18:02Z")
> [@Leo\_Bloom](#): > > 🙂 Excellent. Great rhetorical question, to be saved and used in any number of situations, stupid conversations, etc. You know the reference to turtles wasn’t random, right? > [@Weisshund](#): > > Yes but what better than a simple test thought up by an idiot (scientifically) to be carried out by idiots (literally) 😃 The professional debunker James Randi will only countenance challenges where the results of the challenge are immediately self evident. I can’t speak for Randi and I don’t think I’ve ever heard him say why he has this requirement, in so many words. But I think it is because idiots - and particularly determinedly self-deluding idiots - will find a way to discount the results of any experiment or challenge that cannot be taken in at a glance. It is said that “_justice must not only be done but be seen to be done_”. Similarly, I think that to convince such idiots the results must not only be correct they must be so obviously correct that even an idiot can see it. That’s really the flat earth thing in a nutshell. Of course many purported “believers” are scammers or have their tongue in their cheek. But for many the reason they believe in a flat earth is that’s just the way earth looks from where they are standing. And unless you can provide them with a a proof of a globe earth that is similarly as self evident, they are never going to accept it. ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [June 2, 2017, 4:38am UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/71 "2017-06-02T04:38:35Z")
I guess the real test of the Earth pizza is to take an airplane to the southern ocean (near the edge) and fly west from Ushuaia, keeping the Antarctic coastline at a fairly constant distance. If the Earth was flat, the plane would constantly be bearing to the right to keep from flying into the ice that encircles the world. One should train the FE in flying the airplane, so that they can observe for themself – if that is possible. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [June 2, 2017, 5:14am UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/72 "2017-06-02T05:14:50Z")
But I thought you said they thought the wall of ice was only 200ft high? If so, and if you can find an FE’er who can fly a sufficiently long range plane, why not just get them to fly south from Ushuaia and see what happens? ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [June 2, 2017, 5:27am UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/73 "2017-06-02T05:27:19Z")
Honestly, I think I would be disinclined to engage FEs in debate the first place. They can believe whatever they want to believe, as they are so very fringe that they harm no one. Though, it is an interesting thought experiment, to prove heliocentrism conclusively to a person standing on the ground. It is kind of difficult. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [June 2, 2017, 6:02am UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/74 "2017-06-02T06:02:18Z")
> [@eschereal](#): > > Honestly, I think I would be disinclined to engage FEs in debate the first place. They can believe whatever they want to believe, as they are so very fringe that they harm no one. Though, it is an interesting thought experiment, to prove heliocentrism conclusively to a person standing on the ground. It is kind of difficult. It depends on the level of abstraction they can cope with. For example, to me, [ul][li]I can stand on the ground in the very early morning and evening and see bright specks of light going overhead. [/li] [li]I can look on websites and see that people are able to predict, to the second, when those bright specks will go over. [/ul][/li]The only plausible way I can explain these two facts is by assuming that the people running the websites understand really well the way the bright specks move. And those people say the earth is a globe. I think they must know what they are talking about. There are alternative explanations; there could be a worldwide conspiracy of astronomers who know the earth is flat but just lie about how they _actually_ predict the positions of the bright specks. Or I guess the bright specks might move in a way that _exactly imitates_ the way the specks would move if the earth was a globe (even though it isn’t one). But both of these theories seem immensely implausible. ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [June 2, 2017, 6:24am UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/75 "2017-06-02T06:24:52Z")
What they say is that the Earth is a pizza and the sun-lamp-thing moves in a circle above it. That the sunset is just an illusion of perspective (it only appears to be setting because it looks close to the horizon because it is so far away). This glaring flaw in this argument is that you can watch a sunset and see the sun get _bigger_ as it crosses the horizon – as with the harvest moon. I cannot see how the perspective model could address that. For most of the day, the sun subtends exactly the same angle, except at sunrise and sunset, when it is supposed to be farther away but somehow looks bigger. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [June 2, 2017, 6:52am UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/76 "2017-06-02T06:52:01Z")
> [@Colophon](#): > > The round table analogy is meant to show that the horizon itself is flat, the same as the rim of a table is flat. (Of course, the ground between you and the horizon isn’t flat, so a better analogy would be a slightly domed circular table.) You’re not seeing the curvature of the Earth, you’re seeing the curve of the “rim”, which will look more curved the more you look “down” on it. But the earth is not flat or even “slightly domed”, any curve in the rim is the same as the curve of the dome therefore if you are high enough to perceive the curve of the rim, you are effectively seeing the curve of the dome and therefore the curvature of the earth. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [June 2, 2017, 9:07am UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/77 "2017-06-02T09:07:05Z")
> [@Richard\_Pearse](#): > > But the earth is not flat or even “slightly domed”, any curve in the rim is the same as the curve of the dome therefore if you are high enough to perceive the curve of the rim, you are effectively seeing the curve of the dome and therefore the curvature of the earth. No you’re not. The rim is not curved “up and down”, it is flat, totally horizontal. Think about it: the horizon is the set of points that are as far away as you can see over the curve of the earth. It is the intersection between a cone centred at your eye and the surface of the Earth, therefore it is a circle. (Ignoring local topography, of course). You can ignore the curve of the Earth between you and the horizon, because _by definition_ you are looking over the top of it, and it is not blocking your view of the horizon. You might as well imagine slicing a small portion off the Earth, centred under your feet, and defined by the circle of the horizon. That circle is totally flat, regardless of what the ground you sliced off is doing. The higher up you go, the more you are looking down on this circle (and meanwhile the circle is getting bigger because you can see further to the horizon), so the more it looks like a circle rather than a straight line, until you get to the extreme case where you are out in space and you can see the whole circle of the horizon, which will get closer and closer to the circumference of the Earth the further away you get. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [June 2, 2017, 9:14am UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/78 "2017-06-02T09:14:44Z")
> [@Andy\_L](#): > > You can use the levelness of water in a simpler way. Build a large pool, in a rectangular shape. Make sure the sides are absolutely straight - then fill it with water. You’ll find that water drains off the short sides, because of the curvature of the Earth, if the pool is large enough. > > For that matter, try to create anything that is both straight (measured by laser) and level throughout (measured by spirit level) - at some point, these requirements will conflict. As had to be compensated for by some rather clever engineering when they were building the [LIGO observatory](https://dcc.ligo.org/public/0072/P000006/000/P000006-D.pdf), each site of which consists of two 4km-long tubes, which had to be laser-straight. > [@](#): > > The beam tubes needed to be aligned > along the propagation direction of light in vacuum and not > along the direction perpendicular to local gravity on the surface > of the Earth. The curvature of the Earth will cause the > Earth’s surface to deviate from the straight line propagated > by light in vacuum by 1.25 m over a 4 km path if the line > starts out level with the surface. The alignment was, therefore, > not the same as that for a level highway or pipeline. In other words, the ends of the tubes had to be about 4ft higher than they would be if they were gravitationally level. ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [June 2, 2017, 12:15pm UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/79 "2017-06-02T12:15:53Z")
> [@Colophon](#): > > As had to be compensated for by some rather clever engineering when they were building the [LIGO observatory](https://dcc.ligo.org/public/0072/P000006/000/P000006-D.pdf), each site of which consists of two 4km-long tubes, which had to be laser-straight. > > In other words, the ends of the tubes had to be about 4ft higher than they would be if they were gravitationally level. Thanks! A great example of what I was thinking of. ---
**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:** [June 2, 2017, 12:28pm UTC](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748/80 "2017-06-02T12:28:37Z")
Not, of course, that any argument involving LIGO is likely to carry any weight at all with a flat-earther. [Previous page](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748.md?page=3) [Next page](https://boards.straightdope.com/t/what-is-the-point-to-flat-earth/787748.md?page=5)