# DIY: Testing Earth's curvature. Clear assumptions, proposition of two experiment. **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [February 23, 2014, 5:11pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023 "2014-02-23T17:11:14Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![karol](https://avatars.discourse-cdn.com/v4/letter/k/977dab/32.png) [@karol](https://boards.straightdope.com/u/karol)\ **Post date:** [February 23, 2014, 5:11pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/1 "2014-02-23T17:11:14Z")
Is it convex or concave ? This thread is not a joke. I count on normal and essential discussion 🙂 > [@](#): > > The Earth curves faster than most people think. On a small lake — say, 2.5 miles across — there’s a 1-foot-tall bulge in the middle of the lake due to the curvature of the Earth. On some larger bodies of water, if conditions are right, you can actually perceive the curvature of the Earth when this sort of bulge **blocks your view of the opposing shore.** [http://www.dummies.com/how-to/content/how-to-determine-the-distance-to-the-horizon.html](http://www.dummies.com/how-to/content/how-to-determine-the-distance-to-the-horizon.html) Is the above true ? Is there really a bulge in the middle of the lake due to its **convexity**? The Polish guy proved there isn’t… Proposition of two experiments: - 1.is based on optical zooming (you can use a camera, camcorder, binoculars, telescope, etc.) - 2.you would need a strong enough laser. If you don’t have one you can even use long enough tape or rope. Instruction here: [http://ow.ly/tPuO0](http://ow.ly/tPuO0) ---
**Author:** ![PlainLost](https://avatars.discourse-cdn.com/v4/letter/p/ac8455/32.png) [@PlainLost](https://boards.straightdope.com/u/PlainLost)\ **Post date:** [February 23, 2014, 5:23pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/2 "2014-02-23T17:23:18Z")
Why use shortened URLs inside internet? ---
**Author:** ![standingwave](https://avatars.discourse-cdn.com/v4/letter/s/9de0a6/32.png) [@standingwave](https://boards.straightdope.com/u/standingwave)\ **Post date:** [February 23, 2014, 5:34pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/3 "2014-02-23T17:34:00Z")
> [@karol](#): > > Is it convex or concave ? > This thread is not a joke. I count on normal and essential discussion 🙂 > > [How to Determine the Distance to the Horizon](http://www.dummies.com/how-to/content/how-to-determine-the-distance-to-the-horizon.html) > > Is the above true ? Is there really a bulge in the middle of the lake due to its **convexity**? The Polish guy proved there isn’t… > Proposition of two experiments: > > - 1.is based on optical zooming (you can use a camera, camcorder, binoculars, telescope, etc.) > - 2.you would need a strong enough laser. If you don’t have one you can even use long enough tape or rope. > > Instruction here: > > [Is Earth convex or concave ? - Dokumenty Google](http://ow.ly/tPuO0) Sounds about right. I’ve heard it as 8 inches of curvature over 1 mile which would work out to an 8 inch bulge spanning 2 miles. Not sure that you can actually notice that small amount standing on shore with your eyeballs ~5 feet above the ground and waves and stuff but the effect is there. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [February 23, 2014, 5:36pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/4 "2014-02-23T17:36:33Z")
> [@PlainLost](#): > > Why use shortened URLs inside internet? Permit me to introduce you to [Bitly](https://bitly.com), which allows you to take the often ginormous links that go to complex websites and compress them into a much shorter hash (and, as an aside, allows easy access tracking and user data aggregation for site owners). Stranger ---
**Author:** ![Twoflower](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/twoflower/32/22_2.png) [@Twoflower](https://boards.straightdope.com/u/Twoflower)\ **Post date:** [February 23, 2014, 6:19pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/5 "2014-02-23T18:19:02Z")
> [@](#): > > The Earth curves faster than most people think. On a small lake — say, 2.5 miles across — there’s a 1-foot-tall bulge in the middle of the lake due to the curvature of the Earth. On some larger bodies of water, if conditions are right, you can actually perceive the curvature of the Earth when this sort of bulge blocks your view of the opposing shore. I’ve observed this effect on Lake Tahoe. It’s definitely real, regardless of what the OP thinks. ---
**Author:** ![karol](https://avatars.discourse-cdn.com/v4/letter/k/977dab/32.png) [@karol](https://boards.straightdope.com/u/karol)\ **Post date:** [February 23, 2014, 7:04pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/6 "2014-02-23T19:04:08Z")
He made pictures of the opposing shore (link in first post) with camcorder placed 50 cm above water surface. The visibility range for this height is 2,5 km. The shore is 5,65 km away though. ---
**Author:** ![Twoflower](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/twoflower/32/22_2.png) [@Twoflower](https://boards.straightdope.com/u/Twoflower)\ **Post date:** [February 23, 2014, 7:06pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/7 "2014-02-23T19:06:41Z")
Far more likely to do with atmospheric distortion (e.g. “mirage”) than concave lake surface. It’s not at all unusual to be able to see things that are theoretically below the horizon because of atmospheric effects. ---
**Author:** ![karol](https://avatars.discourse-cdn.com/v4/letter/k/977dab/32.png) [@karol](https://boards.straightdope.com/u/karol)\ **Post date:** [February 23, 2014, 7:39pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/8 "2014-02-23T19:39:09Z")
> [@Twoflower](#): > > Far more likely to do with atmospheric distortion (e.g. “mirage”) than concave lake surface. It’s not at all unusual to be able to see things that are theoretically below the horizon because of atmospheric effects. But the camera is placed…below the calculable convexity for 5,65 km which is **62 cm.** ---
**Author:** ![74westy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/74westy/32/3950_2.png) [@74westy](https://boards.straightdope.com/u/74westy)\ **Post date:** [February 23, 2014, 8:09pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/9 "2014-02-23T20:09:28Z")
> [@karol](#): > > > [@Twoflower](#): > > > > Far more likely to do with atmospheric distortion (e.g. “mirage”) than concave lake surface. It’s not at all unusual to be able to see things that are theoretically below the horizon because of atmospheric effects. > > But the camera is placed…below the calculable convexity for 5,65 km which is **62 cm.** Aren’t you making Twoflower’s point? ---
**Author:** ![karol](https://avatars.discourse-cdn.com/v4/letter/k/977dab/32.png) [@karol](https://boards.straightdope.com/u/karol)\ **Post date:** [February 23, 2014, 8:13pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/10 "2014-02-23T20:13:39Z")
> [@74westy](#): > > Aren’t you making Twoflower’s point? Nope. Think about it. It’s about the physical barrier (supposed bulge in the middle of the lake due to convexity) that should block the view but it doesn’t. The laser experiment proposed in the article I gave a link to would be surely much more spectacular and leave no doubts. But that will be hard to perform…I mean, who’s got a laser like that ? ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [February 23, 2014, 8:17pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/11 "2014-02-23T20:17:36Z")
> [@Twoflower](#): > > Far more likely to do with atmospheric distortion (e.g. “mirage”) than concave lake surface. It’s not at all unusual to be able to see things that are theoretically below the horizon because of atmospheric effects. It’s also not unusual to see doubled, upside-down ships (or other objects) under some conditions (I have), and these conditions are only applicable very close to the water surface and at sufficient distances, exactly where this test is done. If you are testing for concavity or convexity, it is necessary to eliminate or compensate for these effects. ---
**Author:** ![Twoflower](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/twoflower/32/22_2.png) [@Twoflower](https://boards.straightdope.com/u/Twoflower)\ **Post date:** [February 23, 2014, 8:40pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/12 "2014-02-23T20:40:16Z")
> [@karol](#): > > Nope. Think about it. It’s about the physical barrier (supposed bulge in the middle of the lake due to convexity) that should block the view but it doesn’t. The laser experiment proposed in the article I gave a link to would be surely much more spectacular and leave no doubts. But that will be hard to perform…I mean, who’s got a laser like that ? But that is exactly the point. Atmospheric effects distort the light from the observed objects, making them visible, even though they would be out of view if the light traveled in a straight line. So the effect you’ve described is either caused but this common, easily observed phenomenon, or else by a totally-against-the-known-laws-of-physics concave curvature of the lake surface. You decide. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [February 23, 2014, 8:45pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/13 "2014-02-23T20:45:11Z")
**karol,** are you aware that light (even laser light) may not travel in a straight line under certain conditions? And this experiment is flawed if that happens? ---
**Author:** ![karol](https://avatars.discourse-cdn.com/v4/letter/k/977dab/32.png) [@karol](https://boards.straightdope.com/u/karol)\ **Post date:** [February 24, 2014, 6:27am UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/14 "2014-02-24T06:27:20Z")
Again, because I don’t think you read the article at all 🙂 There is supposedly a bulge in the middle of the lake or any other water reservoir and it can be easily calculated. This bulge is supposed to block the view of the opposing shore. But it does not. We can see reflection of the shore on the water surface. Now imagine that the laser beam below is a really long tape or rope. If you tied it to one shore at the height of **20 cm** and went in a boat to the other shore that is 7 km away (calculable convexity in the middle of such lake is **98 cm** ) what should happen to the rope ? It should…sink. Instead, the distance between the rope and the water surface will…rise till we reach the middle of the lake and then it will…decrease. Same with laser, it will either hit the water instead of the reader or it will hit the reader because of the… **concavity.** [http://i.imgur.com/HFDXS6v.jpg?1](http://i.imgur.com/HFDXS6v.jpg?1) ---
**Author:** ![Twoflower](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/twoflower/32/22_2.png) [@Twoflower](https://boards.straightdope.com/u/Twoflower)\ **Post date:** [February 24, 2014, 6:52am UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/15 "2014-02-24T06:52:50Z")
You’re still insisting that the light beam will remain perfectly straight, despite atmospheric effects that are well known and which will bend the light beam. That assumption is utterly incorrect. ---
**Author:** ![Twoflower](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/twoflower/32/22_2.png) [@Twoflower](https://boards.straightdope.com/u/Twoflower)\ **Post date:** [February 24, 2014, 6:58am UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/16 "2014-02-24T06:58:06Z")
[Atmospheric refraction](http://en.wikipedia.org/wiki/Atmospheric_refraction) ---
**Author:** ![karol](https://avatars.discourse-cdn.com/v4/letter/k/977dab/32.png) [@karol](https://boards.straightdope.com/u/karol)\ **Post date:** [February 24, 2014, 6:59am UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/17 "2014-02-24T06:59:59Z")
> [@Twoflower](#): > > You’re still insisting that the light beam will remain perfectly straight, despite atmospheric effects that are well known and which will bend the light beam. That assumption is utterly incorrect. You still don’t seem to understand but there’s another point. There’s no so called downward refraction 🙂 [http://i.imgur.com/p3TYia0.jpg?1](http://i.imgur.com/p3TYia0.jpg?1) Watch this in your free time: [http://www.youtube.com/watch?v=DaaswxqEvEk](http://www.youtube.com/watch?v=DaaswxqEvEk) captions and annotations. ---
**Author:** ![Tabby\_Cat](https://avatars.discourse-cdn.com/v4/letter/t/6a8cbe/32.png) [@Tabby\_Cat](https://boards.straightdope.com/u/Tabby_Cat)\ **Post date:** [February 24, 2014, 7:46am UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/18 "2014-02-24T07:46:29Z")
You guys are really persistent about this. Kudos, fighting ignorance and all. As for Ms. Karol, well done. You’ve proven that the earth is convex, and that we all live on a rotating wheel space station. Moon thing, spaceships, all that are hoaxes. Good job, we can all sleep easy now. (might want to up the dose a little) ---
**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:** [February 24, 2014, 3:26pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/19 "2014-02-24T15:26:30Z")
A few points: 1.) This was experimentally tested in Norfolk England, first resulting in a finding that the earth was flat (!). More careful measurements later proved the earth convex (whew!) The effect of atmospheric refraction on the results has been noted: > **[Bedford Level experiment](https://en.wikipedia.org/wiki/Bedford_Level_experiment)** > > The Bedford Level experiment is a series of observations carried out along a 6-mile (9.7 km) length of the Old Bedford River on the Bedford Level of the Cambridgeshire Fens in the United Kingdom, during the 19th and early 20th centuries, to measure the curvature of the Earth. > Samuel Birley Rowbotham, who conducted the first observations starting in 1838, claimed that he had proven the Earth to be flat. However, in 1870, after adjusting Rowbotham's method to avoid the effects of atmospheric ref... 2.) Cyrus Teed (“Koresh”) and his Koershans backed a similar experiment by Ulysses Grant Morrow in 1896 along the Illinois Drainage Canal, which proved the earth concave, just as Teed believed. Critics blamed atmospheric refraction. (Same cite. see also Martin Gardner’s _Fads and Fallcies in the Name of Science_. Alsi _The Big Book of Weirdos_) 3.) In Hal Clements science fiction classic _Mission of Gravity_, the Mesklinites, living on a high-gravity planet, are convinced that they live in a bowl-shaped environment. They know it isn’t flat, because they’ve worked out the geometry. But it _looks_ like a concave surface to them, because in their case, atmospheric refraction is severe. ---
**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:** [February 24, 2014, 3:32pm UTC](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023/20 "2014-02-24T15:32:24Z")
> [@CalMeacham](#): > > A few points: > > 1.) This was experimentally tested in Norfolk England, first resulting in a finding that the earth was flat (!). More careful measurements later proved the earth convex (whew!) The effect of atmospheric refraction on the results has been noted: > > [Bedford Level experiment - Wikipedia](http://en.wikipedia.org/wiki/Bedford_Level_experiment) > > 2.) Cyrus Teed (“Koresh”) and his Koershans backed a similar experiment by Ulysses Grant Morrow in 1896 along the Illinois Drainage Canal, which proved the earth concave, just as Teed believed. Critics blamed atmospheric refraction. (Same cite. see also Martin Gardner’s _Fads and Fallcies in the Name of Science_. Alsi _The Big Book of Weirdos_) > > 3.) In Hal Clements science fiction classic _Mission of Gravity_, the Mesklinites, living on a high-gravity planet, are convinced that they live in a bowl-shaped environment. They know it isn’t flat, because they’ve worked out the geometry. But it _looks_ like a concave surface to them, because in their case, atmospheric refraction is severe. In “Project: Genius” by William Hayes, a high school student attempts this kind of experiment, and at first, discovers that the Earth is flat, before realizing the need to correct for refraction. [Next page](https://boards.straightdope.com/t/diy-testing-earths-curvature-clear-assumptions-proposition-of-two-experiment/682023.md?page=2)