# DIY: Testing Earth's curvature. Clear assumptions, proposition of two experiment.

Is it convex or concave ?
This thread is not a joke. I count on normal and essential discussion

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 isnâ€™tâ€¦
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 donâ€™t have one you can even use long enough tape or rope.

Instruction here:

http://ow.ly/tPuO0

Why use shortened URLs inside internet?

Sounds about right. Iâ€™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.

Permit me to introduce you to Bitly, 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

Iâ€™ve observed this effect on Lake Tahoe. Itâ€™s definitely real, regardless of what the OP thinks.

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.

Far more likely to do with atmospheric distortion (e.g. â€śmirageâ€ť) than concave lake surface. Itâ€™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 placedâ€¦below the calculable convexity for 5,65 km which is 62 cm.

Arenâ€™t you making Twoflowerâ€™s point?

Nope. Think about it. Itâ€™s about the physical barrier (supposed bulge in the middle of the lake due to convexity) that should block the view but it doesnâ€™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 performâ€¦I mean, whoâ€™s got a laser like that ?

Itâ€™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.

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 youâ€™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.

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?

Again, because I donâ€™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 shouldâ€¦sink.
Instead, the distance between the rope and the water surface willâ€¦rise till we reach the middle of the lake and then it willâ€¦decrease.
Same with laser, it will either hit the water instead of the reader or it will hit the reader because of theâ€¦concavity.

http://i.imgur.com/HFDXS6v.jpg?1

Youâ€™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 donâ€™t seem to understand but thereâ€™s another point. Thereâ€™s no so called downward refraction

http://i.imgur.com/p3TYia0.jpg?1
Watch this in your free time:

As for Ms. Karol, well done. Youâ€™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)

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:

http://en.wikipedia.org/wiki/Bedford_Level_experiment

2.) Cyrus Teed (â€śKoreshâ€ť) 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 Gardnerâ€™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 isnâ€™t flat, because theyâ€™ve worked out the geometry. But it looks like a concave surface to them, because in their case, atmospheric refraction is severe.

In â€śProject: Geniusâ€ť 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.