[Bobby Shafto]

A flat earth YouTuber made this challenge.

Set a narrow pipe up level on a hill or mountain that has views to an ocean horizon 180° apart. Sight the horizon centered through the tube from one end, then go around to the other end and see if the horizon is centered in that view.

I don't have a vantage point that fits the bill, exactly. I can gain a vantage point on Cabrillo Point that is ~400' elevation with no land fall along a southerly line of sight all the way to Antarctica. But 180° away from that direction, I only get 50-some miles before the line of sight crosses inland at San Onofre and then the Santa Ana mountain range beyond at around 70 miles.



Here's the question: on a globe, from 400' the visual horizon should be around 25-30 miles, well before landfall at San Onofre. That doesn't mean one can't see land rising up beyond that on a  globe horizon if it is high enough.  I know from experience that I can see the Santa Ana range, including ~5700 Santiago Peak, from that spot if the air is clear.  Clear enough, and with recent snows, I'm sure I could even see 10,000+ ft Mt San Antonio in the San Gabriel mountains, over 100 miles away.

But if I try to perform this pipe experiment, will that backdrop of mountains confuse the issue?

What if I were to do it this way? Mount the pipe on a 48" carpenter's level, set upon a tripod, get it level and then make the first sighting to the south.
On a globe, I'd expect the horizon to be below center. On a flat earth, the horizon should be centered.
Say the horizon is below center. That may not mean "globe." It may just mean I didn't get the level right. So, then adjust the level until the southerly horizon IS centered.
Then, go around and sight to the north.  Centered in the pipe should be eye level line of sight for a flat earth.

Is there anything wrong with that reasoning?

[Tom Bishop]

Is there anything wrong with that reasoning?

Yes. You have already taken pictures showing that the atmosphere affects the height of the horizon at different times.

[Bobby Shafto]

Is there anything wrong with that reasoning?

Yes. You have already taken pictures showing that the atmosphere affects the height of the horizon at different times.

It affects discernment of the horizon at times. Not the height of the horizon. I'd be sure to do this when discernment is not an issue.

Okay then?

(This wasn't my idea. It's what a flat earth proponent challenged "globies" to do.)

[AATW]

Is there anything wrong with that reasoning?

The reasoning is sound. If the horizon rises to eye level, which you have already clearly shown it doesn’t, then if you can see the horizon through the pipe in one direction then you should be able to see the horizon through the pipe in the other direction. The two horizons and the pipe should form a straight line, this is the FE claim.

But Tom does another piece of “heads I win, tails you lose” reasoning which I see he has already preempted.

If your experiment showed that the horizons were at eye level then he would claim that this demonstrates the claim. Obviously that isn’t what you’ll find so he then just claims that you are not observing the true horizon.

Note that even on a flat earth the horizon can’t be at eye level. If your pipe is at altitude and the horizon in either direction is a point on the flat earth then those 3 points cannot be in a straight line. The pipe is above the 2 horizon points so it’s a triangle. That is true regardless of the shape of the earth.

EDIT: I always find this a strange FE claim because even if the earth were flat the horizon wouldn’t be at eye level at altitude and the fact it isn’t is so easily demonstrated.

[Tom Bishop]

But Tom does another piece of “heads I win, tails you lose” reasoning which I see he has already preempted.

I don't believe that we ever issued any challenge to demonstrate any particular tenet of the atmosphere or the horizon. These challenges are entirely things you guys are making up in your head.

This horizon kick you guys are on is particularly bad. Even the couple of sentences in ENAG about it says that the horizon is near eye level in a balloon and practically at eye level from a three story building at sea level.

The horizon being "at eye level" tenet is  mainly used as a tool to show that the horizon ascends as it recedes. If you thought it was a challenge in any manner you were mistaken. Virtually no one disagrees, or likely would have ever disagreed, that the horizon can be modified.

[stack]

But Tom does another piece of “heads I win, tails you lose” reasoning which I see he has already preempted.

I don't believe that we ever issued any challenge to demonstrate any particular tenet of the atmosphere or the horizon. These challenges are entirely things you guys are making up in your head.

This horizon kick you guys are on is particularly bad. Even the couple of sentences in ENAG about it says that the horizon is near eye level in a balloon and practically at eye level from a three story building at sea level.

The horizon being "at eye level" tenet is  mainly used as a tool to show that the horizon ascends as it recedes. If you thought it was a challenge in any manner you were mistaken. Virtually no one disagrees, or likely would have ever disagreed, that the horizon can be modified.

But Tom does another piece of “heads I win, tails you lose” reasoning which I see he has already preempted.

I don't believe that we ever issued any challenge to demonstrate any particular tenet of the atmosphere or the horizon. These challenges are entirely things you guys are making up in your head.

This horizon kick you guys are on is particularly bad. Even the couple of sentences in ENAG about it says that the horizon is near eye level in a balloon and practically at eye level from a three story building at sea level.

The horizon being "at eye level" tenet is  mainly used as a tool to show that the horizon ascends as it recedes. If you thought it was a challenge in any manner you were mistaken. Virtually no one disagrees, or likely would have ever disagreed, that the horizon can be modified.

Seems pretty clear from the wiki (my bolding):

"A fact of basic perspective is that the line of the horizon is always at eye level with the observer."

That's not "near" or "practically". That's "always".

[Pete Svarrior]

(This wasn't my idea. It's what a flat earth proponent challenged "globies" to do.)

Why are you avoiding naming the proponent, or providing his/her own explanation of the challenge? Trust issues aside, it would be best not to rely on just one party's interpretation, don't you think?

[Bobby Shafto]

Why are you avoiding...?

Antonio Subirats.

So 2 TFES flat earthers heard from, neither of whom seem to support the premise of this challenge experiment.

[Pete Svarrior]

Why is it so difficult to get a link out of you? Instead of saying "this is totally what this guy is saying, honest," just show us.

[Bobby Shafto]

He has hours of archived YouTube hangouts. I didn't think it would be necessary to locate the actual segments where he's issued that challenge. But for you, Pete, I'll find it.

https://www.youtube.com/watch?v=P7GRU84ALhM&t=5645

[Bobby Shafto]

Is this a "Tom said a thing" thing? Or is Tom speaking for "we?"

This is a rather astounding response, considering I started that horizon topic in April and through all of that, never did you discount the "always at eye level" tenet. Not too long ago, you did seem to relent and concede that it wasn't "always" but that turned out to be a discernment issue, as in sometimes conditions will cause the horizon to appear to drop. I agree with that. But you weren't conceding that, if conditions were good enough, the horizon would appear at eye level.

Now, apparently, you are conceding? And I suppose it's what you meant along? The horizon always rises nearly to eye level?

I'm glad I asked, because I was working under the understanding all these months that it was a flat earth principle (except for advocates of a flat earth model that incorporates EAT or something akin to it where light curves away from the surface of the flat earth) that the horizon was always at eye level regardless of observer elevation. If that's not true, then this proposed test is pointless. 

[Bobby Shafto]

Rhetorical questions: who authored this and does it represent a Flat Earth Society claim or just that of the author?

"A fact of basic perspective is that the line of the horizon is always at eye level with the observer."

I will get off the horizon kick (at least on this forum) if that "fact of basic perspective" is being retracted.

[Tom Bishop]

In FET the true horizon is always at eye level, and moves with you. Whether you can see that is another story. The error we made was in the wiki, by leaving out that you may not be able to see it.

I still do think that many of those experiments which involve aligning a device close to you with a very distant horizon are easily flawed, however. I do also believe that at sea level the horizon is probably very close to eye level.

Per your picture above, with the straight lines, that is addressed in ENAG:

http://www.sacred-texts.com/earth/za/za32.htm

The error in perspective, which is almost universally committed, consists in causing lines dissimilarly distant from the eye-line to converge to one and the same vanishing point. Whereas it is demonstrable that lines most distant from an eye-line must of necessity converge less rapidly, and must be carried further over the eye-line before they meet it at the angle one minute, which constitutes the vanishing point.

...

The theory which affirms that all parallel lines converge to one and the same point on the eye-line, is an error. It is true only of lines equi-distant from the eye-line; lines more or less apart meet the eye-line at different distances, and the point at which they meet is that only where each forms the angle of one minute of a degree, or such other angular measure as may be decided upon as the vanishing point. This is the true law of perspective as shown by nature herself; any idea to the contrary is fallacious, and will deceive whoever may hold and apply it to practice.

[Bobby Shafto]

In FET the true horizon is always at eye level, and moves with you. Whether you can see that is another story.

If you can't see it, then how do you know it's always at eye level and moves with you? 

I'm a zetetic. I want to test that claim about the true horizon. How can I do that? 

It's a super clear day today with winds having blown out all the haze and marine layer moisture. Is what I see today not the true horizon?

[AATW]

In FET the true horizon is always at eye level, and moves with you. Whether you can see that is another story. The error we made was in the wiki, by leaving out that you may not be able to see it.

Honestly. This makes my head spin. In your FAQ you say that your evidence for a FE is:

derived from many different facets of science and philosophy. The simplest is by relying on ones own senses to discern the true nature of the world around us. The world looks flat, the bottoms of clouds are flat, the movement of the Sun; these are all examples of your senses telling you that we do not live on a spherical heliocentric world. This is using what's called an empirical approach, or an approach that relies on information from your senses

My emphasis, but you do often highlight the importance of empiricism. Now you are claiming that the “true” horizon is always at eye level. Your evidence for that is observations and testimony from people who say that the horizon remained “practically” at eye level at altitude.
But then when you are shown observations which demonstrate the horizon dips below eye level you claim that we are not seeing the “true” horizon?
If you’re going to claim to care about empirical evidence you can’t only cite it when it backs up your claim and ignore it when it doesn’t.

[Tom Bishop]

In FET the true horizon is always at eye level, and moves with you. Whether you can see that is another story.

If you can't see it, then how do you know it's always at eye level and moves with you? 

I'm a zetetic. I want to test that claim about the true horizon. How can I do that? 

It's a super clear day today with winds having blown out all the haze and marine layer moisture. Is what I see today not the true horizon?

You should first start by demonstrating the premise of your methods. You should show that all lines would converge at the eye level, not just assume so.

JTolan has shown that some of these methods and assumptions don't make sense on either a globe earth or a Flat Earth. See the folllowing video at 16:02: https://youtu.be/-7M107rgdmM

In FET the true horizon is always at eye level, and moves with you. Whether you can see that is another story. The error we made was in the wiki, by leaving out that you may not be able to see it.

Honestly. This makes my head spin. In your FAQ you say that your evidence for a FE is:

derived from many different facets of science and philosophy. The simplest is by relying on ones own senses to discern the true nature of the world around us. The world looks flat, the bottoms of clouds are flat, the movement of the Sun; these are all examples of your senses telling you that we do not live on a spherical heliocentric world. This is using what's called an empirical approach, or an approach that relies on information from your senses

My emphasis, but you do often highlight the importance of empiricism. Now you are claiming that the “true” horizon is always at eye level. Your evidence for that is observations and testimony from people who say that the horizon remained “practically” at eye level at altitude.
But then when you are shown observations which demonstrate the horizon dips below eye level you claim that we are not seeing the “true” horizon?
If you’re going to claim to care about empirical evidence you can’t only cite it when it backs up your claim and ignore it when it doesn’t.

You have to start from first principles. Use your senses to understand the true nature of perspective, like Rowbotham did. Not just wildly assume things and post debunk videos. Assumptions of perspective must be shown by nature.

If you study perspective closely, you can understand what is happening. I would recommend reading Earth Not a Globe by Samuel Birley Rowbotham, as a start, to know what you will need to look into.

[Tom Bishop]

Per Earth Not a Globe, the best way to do this experiment is to align the pipe with two known bodies in the distance, such as in Experiment 9: http://www.sacred-texts.com/earth/za/za14.htm

Then no one can tell you that the horizon was a little foggy in the distance. Rowbotham did think of all of these considerations when designing his experiments.

[edby]

Per Earth Not a Globe, the best way to do this experiment is to align the pipe with two known bodies in the distance, such as in Experiment 9: http://www.sacred-texts.com/earth/za/za14.htm

Then no one can tell you that the horizon was a little foggy in the distance. Rowbotham did think of all of these considerations when designing his experiments.

This would be a good experiment. Rowbotham's assumptions agree with the curve calculator https://www.metabunk.org/curve, such as the horizon being 6 miles away. The question is whether his main claim is correct.

The distance across St. George's Channel, between Holyhead and Kingstown Harbour, near Dublin, is at least 60 statute miles. It is not an uncommon thing for passengers to notice, when in, and for a considerable distance beyond the centre of the Channel, the Light on Holyhead Pier, and the Poolbeg Light in Dublin Bay, as shown in fig. 23.

[EDIT] See my OP here.

[AATW]

You have to start from first principles. Use your senses to understand the true nature of perspective, like Rowbotham did. Not just wildly assume things and post debunk videos. Assumptions of perspective must be shown by nature.

That’s a complete fudge of a response.
I honestly don’t know how else one could investigate the matter of where the horizon is other than making observations. When I look out to sea the sharp line (on a clear day) where the sea ends and the sky starts is the horizon. That is not a wild assumption, it’s a definition:

“The line at which the earth's surface and the sky appear to meet”

If that line is shown to be below eye level at altitude, and the amount it is below eye level increases with altitude - and Bobby has shown this result very clearly - then it’s utterly nonsensical to claim that the line is not the “true horizon”. That line IS the horizon, by definition.

[Bobby Shafto]

In FET the true horizon is always at eye level, and moves with you. Whether you can see that is another story.

If you can't see it, then how do you know it's always at eye level and moves with you? 

I'm a zetetic. I want to test that claim about the true horizon. How can I do that? 

It's a super clear day today with winds having blown out all the haze and marine layer moisture. Is what I see today not the true horizon?

You should first start by demonstrating the premise of your methods...

Why is the onus on me? You made a big deal in another topic about positive claims. Just earlier, you made a positive claim. So, how do YOU substantiate that claim?

The premise of my methods, as you put it, is your claim: the horizon is always at eye level. So, how do you know?  What's YOUR method to check whether that's true or not?