[Max_Almond]

The guy above was perhaps the first one to pioneer the use of these tubes - he's a flat earther, but usually only posts videos from sea level, so they don't really show anything. He has done it at least once from elevation though, and observed the dip of the horizon - but, for some reason, he doesn't talk about that.

Here's a shot I took from 1500 feet:



The mountains there are between 3500 and 5000 feet, around 70-80 miles away. So as we see, not only is the horizon below eye level, but much higher mountains, and the sun itself, which is supposed to be several thousand miles high.

It's an excellent and elegantly simple proof of the curve of the earth for those who are able to understand and see it.

[TomFoolery]

The guy above was perhaps the first one to pioneer the use of these tubes - he's a flat earther, but usually only posts videos from sea level, so they don't really show anything. He has done it at least once from elevation though, and observed the dip of the horizon - but, for some reason, he doesn't talk about that.

Here's a shot I took from 1500 feet:

...

The mountains there are between 3500 and 5000 feet, around 70-80 miles away. So as we see, not only is the horizon below eye level, but much higher mountains, and the sun itself, which is supposed to be several thousand miles high.

It's an excellent and elegantly simple proof of the curve of the earth for those who are able to understand and see it.

Super nice Max.

But what do you think about the guy's center column being higher than the other two?

[Max_Almond]

Kinda weird: I guess that's for him to figure out why. I once hooked three bottles up together and it wasn't a problem.

Here's a cool infographic for those who maybe struggle to get their heads around it (there are some, I know):

[AATW]

It’s interesting how these experiments show consistent results. If the issue was with configuration then surely we’d sometimes see a horizon above eye level, but we never do.
It’s also interesting that the loudest critic of these experiments refuses to do any himself...

[Max_Almond]

Indeed. Nor do we ever see it at eye level. I've done this so many times now. The results are always the same.

[Tom Bishop]

The way the meniscus is shaped makes it easy for the meniscus to always be too high.



You are looking at the underside of the curve and trying to align something that is not level.

For an experiment like this we need some way to calibrate the tool, to ensure that it is actually accurate and valid.

The fact that a three container version of the device is unable to be calibrated tells us everything we need to know. There is nothing thing saying that the device is accurate or reliable for this purpose. That needs to be demonstrated.

[TomFoolery]

The way the meniscus is shaped makes it easy for the meniscus to always be too high.



You are looking at the underside of the curve and trying to align something that is not level.

For an experiment like this we need some way to calibrate the tool, to ensure that it is actually accurate and valid.

The fact that a three container version of the device is unable to be calibrated tells us everything we need to know. There is nothing thing saying that the device is accurate or reliable for this purpose. That needs to be demonstrated.

Thanks Tom, are you suggesting that  the guy's variation in reading was due to viewing the different meniscii at different angles due to perspective?

Would it be better to have the sight glass part to be much larger in diameter to reduce the effects of the internal cohesion?

Or would it be better to use a liquid metal like mercury or Galinstan?

[Max_Almond]

The ones I used, of course didn't suffer any such meniscus problems, given the size of the bottles. :-)

[ChrisTP]

Yes it is safe to say you can ignore Tom when he brings up Meniscus as a reason because it's such a tiny difference from within bottles. If you were using test tubes that were thin then you might have a problem. That being said I still think it's a pointless experiment to dtermin the shape of the earth either way.

[AATW]

I still think it's a pointless experiment to dtermin the shape of the earth either way.

Agree with this. And the reason for that is because the horizon would dip on a flat earth too.

You can only see a finite distance so on a flat earth the horizon would be the limit of your visibility. But it would be a point (we’ll, a circle really) on the flat earth. So if you’re at altitude then you would be looking down at it:



And the amount you’re looking down at it would increase with altitude assuming that visibility doesn’t increase with altitude, and why would it? The Wiki does try to deal with the fact that the horizon is further away at altitude but the explanation is a bit word salad. In the real world this happens because you can see further over the curve of the earth, on a flat earth you wouldn’t be able to see any further by ascending. Actually I don’t think you would get a sharp horizon on a flat earth, it would be more of a fading out like on a foggy day. Why would there be a sharp line?

These tests clearly show that the horizon dips and the amount of dip increases with altitude. Tom can post as much flimflam as he likes, if this result was because of inaccuracies then you’d get a variety of results - his own diagram with the miniscus shows that you can get an error either way. But that’s not what is observed, the result of horizon dip and increasing dip with altitude is shown consistently using this method and with other methods. So that result is not in dispute apart from by Tom but until he can devise and perform an experiment to show anything to the contrary then no one is taking him seriously.

But I’d expect that result on a flat earth.
What I wouldn’t expect is a sharp horizon line or the distance to the horizon to increase with altitude.

[QED]

I still think it's a pointless experiment to dtermin the shape of the earth either way.

Agree with this. And the reason for that is because the horizon would dip on a flat earth too.

You can only see a finite distance so on a flat earth the horizon would be the limit of your visibility. But it would be a point (we’ll, a circle really) on the flat earth. So if you’re at altitude then you would be looking down at it:



And the amount you’re looking down at it would increase with altitude assuming that visibility doesn’t increase with altitude, and why would it? The Wiki does try to deal with the fact that the horizon is further away at altitude but the explanation is a bit word salad. In the real world this happens because you can see further over the curve of the earth, on a flat earth you wouldn’t be able to see any further by ascending. Actually I don’t think you would get a sharp horizon on a flat earth, it would be more of a fading out like on a foggy day. Why would there be a sharp line?

These tests clearly show that the horizon dips and the amount of dip increases with altitude. Tom can post as much flimflam as he likes, if this result was because of inaccuracies then you’d get a variety of results - his own diagram with the miniscus shows that you can get an error either way. But that’s not what is observed, the result of horizon dip and increasing dip with altitude is shown consistently using this method and with other methods. So that result is not in dispute apart from by Tom but until he can devise and perform an experiment to show anything to the contrary then no one is taking him seriously.

But I’d expect that result on a flat earth.
What I wouldn’t expect is a sharp horizon line or the distance to the horizon to increase with altitude.

Actually, wouldn’t the horizon DECREASE with altitude on a FE?

If vanishing perspective theory posits that there is a maximum distance one can see — and that limit defines the horizon, then if your altitude increases, the horizon should close in on you.

As you rise, the distance to a given point on the ground increases by Pythagorean’s theorem. So one should not be able to see as far as someone can on the ground.

[TomFoolery]

I still think it's a pointless experiment to dtermin the shape of the earth either way.

Agree with this. And the reason for that is because the horizon would dip on a flat earth too.

I agree that on a flat earth, the apparent horizon should be anything but a distinct line, because you're not really looking at the horizon (i.e. the edge) but you're just looking out into so much air you can't see anything farther unless it's really bright like the sun and the moon, then you can see it 10,000 miles away. Which is odd that you can see both the sun and the moon the same distance away even though one's 400,000 times brighter.  On a day where the sun is visible for 12 hours, the moon should be visible for a much shorter period.

But I digress.

Anyway, I suppose we should mention the difference between horizon and apparent horizon.

The classical definition of horizon goes along the lines of "the line that divides all visible directions into two categories: those that intersect the Earth's surface, and those that do not..."

It's obviously a spherical-centric term.

Because on a flat earth, since we (usually) cannot see the real traditional horizon (i.e. the edge) since it may be thousands of miles away, all we see is a gradual gradient transition between the water's surface and the haze. There's no particular line that is the horizon, it is just a point where we can't really see the texture of the water, even though we're looking right at it.

And naturally, the distance (and hence dip) of this line varies drastically based on the clarity of the air that day.

The difficulty comes in when we look out to sea and we see a hard sharp horizon line.

Now as mentioned, on a flat earth, the true physical horizon (i.e the edge) if we could see it would dip increasingly with observer elevation. But very very small, depending on how far you were from the edge.
If you were near the equator, and about 6000 miles from the edge, even a rise of 100,000 feet would only be under 20 miles up, and compared to the 6000 miles distance to the horizon, it would still only be a 0.2 degree dip.
At levels like 35,000 feet, it would be only 0.065 degrees.

So the difficulty comes in when we realize that the horizon does show a hard sharp line, even at distances of a few miles if you're down near sea level, and that the horizon dips much much more drastically than a flat earth allows as the observer goes up in elevation.

In fact, if we make our water level 57.3 inches long then each degree will be one inch, so you can use an inch ruler to measure degrees above or below eye level. (At least for the first few degrees.)

For the metric folks, just make your water level 57.3cm long and use a cm ruler to measure degrees.

(Obviously if you wanted it accurate for more than a few degrees from eyelevel, you'd want to use a curved ruler, which was curved around the radious of 57.3.)

The horizon moves away very drastically with even small increases in elevation; specifically, it goes from around 3 miles standing on the beach to 8 miles at 50 ft elevation and 12 miles at 100ft elevation, to 39 miles at 1000ft elevation.

And all on the same day. How can going from observer eyelevel 6ft to observer eyelevel 50ft more than double the distance to the horizon?

Furthermore, things are often visible beyond the horizon, if they stick up enough. If the atmosphere only allows the water to be visible to 8 miles when I'm standing on the beach, then how is it possible for me to literally be seeing mountains 100 miles beyond that?

[Max_Almond]

At the basic level, what this shows is that the old flat earth saying "the horizon always rises to eye level" is wrong, and that everyone who repeated it was also wrong.

It would be hard to find a sensible person who would disagree with that.

At the next level, what we find if we measure the dip angle is that it matches a sphere with a radius of 3959 miles.

Even if there was a horizon on a flat earth - and there's no reason to think there would be - the angles would be much, much smaller.

Observations of the relationship between the horizon and eye level, therefore, are another in a long line of simple flat earth disproofs.

[AATW]

Actually, wouldn’t the horizon DECREASE with altitude on a FE?

If vanishing perspective theory posits that there is a maximum distance one can see — and that limit defines the horizon, then if your altitude increases, the horizon should close in on you.

As you rise, the distance to a given point on the ground increases by Pythagorean’s theorem. So one should not be able to see as far as someone can on the ground.

Interesting. Yes, I think you're right.

The Wiki does have some explanation of viewing distance increasing with altitude, it's complete word salad and contradicts other parts of the same Wiki page but I think this is a different thread:

When you increase your altitude you are changing your perspective lines in relation to the earth, pushing back your vanishing point. The vanishing point, beyond which no man can see, is created when his perspective lines approach each other at a certain angle smaller than the eye can see. If you increase your height you are changing your perspective lines and thus can see further before all sight is lost to the vanishing point

If the earth were flat then the horizon would fade out, as it does in the real world on a foggy day. If the distance to the horizon is further than visibility then you don't get a sharp horizon line:



That's why the horizon as seen from a plane is often not a sharp line.

[ChrisTP]

Couple a non foggy day on a flat earth with a vanishing point you will see what looks like a harsh line horizon with the naked eye, just like you'd see on the actual round earth. A flat disk the size it needs to be for earth would look the same as a globe earth. Even on the top of a mountain. Of course attempting to visually measure a curve is also a mute point since flat earthers will just say the data is skewed from mirages. No flat earther will ever truly believe the data from attempts at measuring the horizon if said data favours a round earth, but the second that data shows anything possibly flat earth related(again, would look the same) they'll jump on it. As AATW says regularly, the confirmation bias is extremely apparent with flat earthers in this case.

It's a pointless experiment because it won't prove anything in favour of flat earth and can be denied all the same as the data is so varied.

[AATW]

Couple a non foggy day on a flat earth with a vanishing point you will see what looks like a harsh line horizon with the naked eye, just like you'd see on the actual round earth. A flat disk the size it needs to be for earth would look the same as a globe earth.

I don't agree with this. I mean, there's no such thing as a vanishing point in real life, is there?
I guess there is a point at which you can't see anything because of the limits of your vision, at that point you could use optical zoom to restore it to sight.
But if you're looking out to sea then that's a massive expanse of water, if it were flat then surely it would just get less clear and fade out like in a fog, I don't see why there would be a sharp line.
And surely you'd be able to use optical zoom to see further and push the horizon back.

[Tom Bishop]

Regardless of whether the horizon is at eye level or not in all circumstances, the experiments used are not even methods that surveyors use. The people doing this experiment are basically just making up surveying science as they go along.

The tool needs to be calibrated. The experiment needs a control. Assuming that it is level or that it is an accurate method is not enough.

[AATW]

The tool needs to be calibrated. The experiment needs a control. Assuming that it is level or that it is an accurate method is not enough.

This is quite funny when "water finds its level" is one of the FE catchphrases.
Stop squirming. Multiple methods have shown this result. This water level one shows a consistent result. If it was only because of inaccuracies or poor calibration then you wouldn't get consistent results like this.
If you want to devise your own experiment to test this claim then please do.

One reason there's no coherent FE theory and there's no progress in making one is your refusal to accept any result which doesn't match Rowbotham's ideas no matter how often or conclusively they are shown to be wrong. And you refuse to do any tests yourself.

[Tom Bishop]

The only valid experiment in this thread was the one which had a control -- the three container version. The three water levels did not line up, which means that we could not trust the alignment of either the front two or back two containers in that device. The third container acts as a necessary litmus test for the hypothesis.

You should look into the subject of scientific integrity.

[QED]

The only valid experiment in this thread was the one which had a control -- the three container version. The three water levels did not line up, which means that we could not trust the alignment of either the front two or back two containers.

You should look into the subject of scientific integrity.

A “control” in this instance would be a container hidden from the viewer (in a box, say). The control would serve to quantify the effect of the meniscus on horizontal readings.

What one would find is that the scale of water tension’s effect on the meniscus is too small to noticeably affect the reading. This is because water tension has relevant effects only in the small wavelength limit. In an experiment where the scale of measurment is much greater than the size scale of the container, water tension can safely be informed.

Learning about what I have detailed above, and explaining this to the experimenters — with the objective of propelling science forward — is indicative of scientific integrity.