[Max_Almond]

Theodolite? Water level? Spirit level?

I want to do an eye level test but I want it FE-approved.

Cheers.

[J-Man]

My understanding is you need to work with an optometrist. Everyone's viewing perspective is different. Do you wear corrective lens, which eye is dominant? Will you be viewing with both eyes or one? Have you trained your eye(s) for extended viewing times and distance? The eye is complex and sailors saw different things on the horizons at virtually the same time. Thus the myth of curved earth.

[Max_Almond]

While I'm a big fan of satire, I am also hopeful that at least a few flat earth believers will take the time to provide an answer to this question: it will be genuinely appreciated.

Cheers.

[totallackey]

IMO, I believe any tool you utilize would need to be portable to the extent of carrying to great heights above the surface of the flat plain of the earth.

I have seen people claiming to have such devices loaded on a smartphone app, utilizing the camera on the smart phone.

I have no idea if they properly work, nor am I aware if the camera on the smartphone would skew the results, having never seen any evidence of confirmation (i.e., two persons side by side using the same app and posting the results simultaneously) or calibration tests by an independent lab.

[ChrisTP]

Water in tubes.

https://flatearth.ws/water-level-horizon

[AATW]

Water in tubes.

https://flatearth.ws/water-level-horizon

I think that's a pretty good way. After all, "water finds its level", right?
So you can be pretty confident that if you're looking across the two connected tubes that you're looking horizontally.
It's also a pretty cheap method which anyone could reproduce with a minimum of expense.

[robinofloxley]

My favorite is this experiment carried out by Critical Think

https://www.youtube.com/watch?v=54FiuS9ZplM&t=63s

in response to a video from Antonio Subirats.

The idea is very simple. Find somewhere reasonably high up where you can see the sea and a clear horizon in front of you and you can also see the sea and a horizon directly behind you (he's at Byron Bay NSW Australia).

Fasten a simple, long straight cardboard tube to a spirit level and a tripod. Stand at one end, adjust the tube so you can see the horizon in the middle when you look down the tube - eye level right?

Now, without touching anything, look down the other end of the tube - you can see the horizon again because it's at eye level - yes? Of course you can't, it's pointing up in the sky and the spirit level confirms the tube isn't level.

Needless to say Antonio Subirats wriggled and squirmed trying to discredit the video. I think at one point complaining for some reason that the experiment was invalid because the tube was made of cardboard. The back and forth ran on for a while and was very entertaining.

[Max_Almond]

The tube test is good. I have a place near me with horizons behind and in front, but don't have a spirit level, so I made two tubes side by side. When one each is pointed at the horizon they reveal...well, we all know what they reveal. ;-)

I've also been doing water levels observations, and will be going up a 1500 foot hill soon to do a whole bunch of observations simultaneously.

In the meantime, here's a photo I took from 600 feet above sea level:



The mountains in the distance are up to 5100 feet tall. The 1500 foot shot is similar, but the sun sets a little more to the left of this range, so I can get both the sun and the horizon below eye level, as well those much higher peaks.

[AATW]

The tube test is pretty much flawless and I'd say the spirit level is superfluous. If the horizon rises to eye level then by definition if you can see the horizon through one end then the tube must be level and you'd be able to see the horizon through the other end of the tube too.

That said, none of this proves a globe earth. Even if the earth were flat the horizon would be below eye level. The horizon would be a point on the earth, you'd still be looking down at it:

[Max_Almond]

Even if the earth were flat the horizon would be below eye level.

If the earth were flat, there wouldn't be a horizon.

And it at least proves that flat earthers have been saying and believing something totally incorrect yet incredibly simple to measure for at least 150 years.

Furthermore, that those pesky idiot 'globers' have been not only telling them they were wrong, but getting it right.

The intellectually developed flat earther here thinks: gee whizz, I wonder what else I've been wrong about, and in which other ways they've been right?

[markjo]

Even if the earth were flat the horizon would be below eye level.

If the earth were flat, there wouldn't be a horizon.

Actually, there would.  The horizon is defined as where earth and sky appear to meet.  That would still be a valid observation regardless of the shape of the earth.

[Max_Almond]

What would cause a horizon on a flat earth? In reality, it's caused by the curve. But a plane would just disappear into haze at an arbitrary, ever-changing distance, much further away than the actual horizon we see every day.

[Tom Bishop]

The following page will give you everything that you need to know: https://wiki.tfes.org/Water_Level_Devices

[ChrisTP]

The following page will give you everything that you need to know: https://wiki.tfes.org/Water_Level_Devices

that article shows water not being level in test tubes where green dye is used more to the right, then states later that dye can cause inconsistencies. It debunked itself...

Then a series of images showing the water device in different locations at different camera angles to show apparent inconsistencies... But of course they are inconsistent because of those changes, not sure what that's trying to show, could you explain?

[Tom Bishop]

The following page will give you everything that you need to know: https://wiki.tfes.org/Water_Level_Devices

that article shows water not being level in test tubes where green dye is used more to the right, then states later that dye can cause inconsistencies. It debunked itself...

Dye is often used in the water level experiments...

[ChrisTP]

The following page will give you everything that you need to know: https://wiki.tfes.org/Water_Level_Devices

that article shows water not being level in test tubes where green dye is used more to the right, then states later that dye can cause inconsistencies. It debunked itself...

Uh, dye is often used in the water level experiments...

you seem to be ignoring the point, the dye is clearly diluted further to the left in the tube, it seems the more green dye there is, the higher the level of liquid which of course could be coincidence, but in that very same article it is also stated that dye has different properties to pure water which can give the liquid varying levels. Why isn’t there a consistent amount of dye used in that set of tubes that show inconsistent levels? How can anyone prove an inconsistency with an inconsistent experiment?

Of course, in that same image there’s no proof that the tubes are even level with the camera used, what’s to stop someone tilting the tubes and the camera?

[Tom Bishop]

The liquid is higher in the smaller tubes mainly because of capillary action. The article is accurate. If the dye plays a part, it would depend on the weight and buoyancy of the dye.

https://courses.umass.edu/plecprep/fluids/2a2010.html



"Description: This is a set of capillary tubes of various diameters used to show capillary rise with water."

Your argument that "dye is used therefore debunked" is pretty weak since most of the water level experiments use dye, and you are therefore arguing that those water level experiments are debunked.

[ChrisTP]

Ok so as long as the tubes are the same width using the same mixture of liquid all should be well. I guess to further measure the accuracy you could also mark the tubes with precise ruler lines to show the liquid is meeting the correct level of the tubes

[Max_Almond]

Ok so as long as the tubes are the same width using the same mixture of liquid all should be well. I guess to further measure the accuracy you could also mark the tubes with precise ruler lines to show the liquid is meeting the correct level of the tubes.

That's well said, Chris - and credit to Tom for pointing out the need to be careful with water levels.

I suppose an easy test to show whether a water level is showing level or not would be to place it on a level surface and measure up to the two surfaces.

[Tom Bishop]

Quite incorrect and undemonstrated. The Britannica article says that the surface tension is not level and there are several examples of the water level experiment giving inconsistent results or being inaccurate. These experiments are jokes, and they give large and differing results.

Show us that water tension is level and always gives the same results.

The closer we get things to our face in the foreground, the more accurate all elements of leveling needs to be. You are assuming that we can just wing it on the imprecise nature water tension and the fact that the water levels are arguably off very slightly in the images.

None can doubt that a slight error in altitude and leveling in the foreground can create a large impact on the background. You are just winging without knowing how precise you need to be.

The errors shown and inconsistency of these experiments invalidates the matter until demonstrated otherwise. Are we to believe that it doesn't matter that the water line kept changing in relation to the bodies in the background? Are we to believe it doesn't matter that the water doesn't line up in some of the devices?

If you want to conduct an experiment you need to really prove the matter and the validity of the tools used.