Please provide some proof or actual hard evidence of your "theory"

Troll trolling a legitimate website.  I thought you would have given up by now, but I was wrong.  Permanoob.

Yawn, feel free to prove that you're not a troll by actually refuting what markjo quoted instead of trying to derail the conversation.

Quote from: jroa on August 15, 2012, 07:45:38 PM

Troll trolling a legitimate website.  I thought you would have given up by now, but I was wrong.  Permanoob.

Yawn, feel free to prove that you're not a troll by actually refuting what markjo quoted instead of trying to derail the conversation.

The section Markjo quoted is clearly not supported by anything. There are not any citations which pertain to that topic. Markjo's section even has [dubious-discuss] in brackets towards the end.

Read Earth not a Globe.

Quote from: Samuel Birley Rowbotham

IF a theodolite is placed on the sea shore, "levelled," and directed towards the sea, the line of the horizon will be a given amount below the cross-hair, and a certain "dip" or inclination from the level position will have to be made to bring the cross-hair and the sea-horizon together. If the theodolite is similarly fixed, but at a greater altitude, the space between the cross-hair and the sea horizon, and the dip of the instrument to bring them together, is also greater.

Did you read the entire chapter?

The author saw at once that this peculiarity depended upon the construction of the instruments. He ascertained that in those of the very best construction, and of the most perfect adjustment, there existed a certain degree of refraction, or, as it is called technically, "collimation," or a slight divergence of the rays of light from the axis of the eye, on passing through the several glasses of the theodolite. He therefore obtained an iron tube, about 18 inches in length; one end was closed, except a very small aperture in the centre; and at the other end cross-hairs were fixed. A spirit level was then attached, and the whole carefully adjusted. On directing it, from a considerable elevation, towards the sea,

p. 42

and looking through the small aperture at one end, the cross-hair at the opposite end was seen to fall to the horizon, as shown at fig. 31. This has been tried in various places, and at different altitudes, and always with the same result; showing clearly that the horizon visible below the cross-hair of an ordinary levelling instrument is the result of refraction, from looking through the various glasses of the telescope; for on looking through an instrument in every respect the same in construction, except being free from lenses, a different result is observed, and one precisely the same as that seen from a balloon, from any promontory, and in the experiment at Brighton, shown in fig. 27, p. 39.

These comparative experiments cannot fail to satisfy any unbiassed observer that in every levelling instrument where lenses are employed, there is, of necessity, more or less divergence of the line of sight from the true or normal axis; and that however small the amount--perhaps inappreciable in short lengths of observation--it is considerable in distances of several miles. Every scientific surveyor of experience is fully aware of this and other peculiarities in all such instruments, and is always ready to make allowances for them in important surveys. As a, still further proof of this behaviour of the telescopic levelling instruments, the following simple experiment may be tried. Select a piece of ground--a terrace, promenade, line of railway, or embankment, which shall be perfectly horizontal for, say, five hundred yards. Let a signal staff, 5 feet high, be erected at one end, and a theodolite or spirit level fixed and carefully adjusted to exactly the

p. 43

same altitude at the other end. The top of the signal will then be seen a little below the cross-hair, although it has the same actual altitude, and stands upon the same horizontal foundation. If the positions of the signal staff and the spirit level be then reversed, the same result will follow.

i was hoping jroa might make something other than a zero-content post for once, but what's dubious in that article is that the difference is too small to be seen with the naked eye in most cases, not that there's a difference.

CET, you are the king of zero-content posts.  What is the saying about glass houses again?

The quote has no legitimate points.  I was pointing that out.

Quote from: Kendrick on August 15, 2012, 05:53:32 PM

Read Earth not a Globe.

Quote from: Samuel Birley Rowbotham

IF a theodolite is placed on the sea shore, "levelled," and directed towards the sea, the line of the horizon will be a given amount below the cross-hair, and a certain "dip" or inclination from the level position will have to be made to bring the cross-hair and the sea-horizon together. If the theodolite is similarly fixed, but at a greater altitude, the space between the cross-hair and the sea horizon, and the dip of the instrument to bring them together, is also greater.

Did you read the entire chapter?

I did - did I miss a part where he said the horizon actually does come up to the level-line in a levelled theodolite?  Because it appears to me that he's sheepishly attempting to explain it away.

You asked for a source that stated the horizon does not meet you at eye level when looking through a theodolite - you have one, I'm frankly surpised you werent aware of it.

The quote has no legitimate points.  I was pointing that out.

I thought you were merely stating a fact that we could read into however we wanted to?

Odd how your story changes.

Quote from: jroa on August 15, 2012, 09:20:09 PM

The quote has no legitimate points.  I was pointing that out.

I thought you were merely stating a fact that we could read into however we wanted to?

Odd how your story changes.

How did I contradict myself, you troll?

How did I contradict myself, you troll?

Name calling, how extremely inappropriate.  I'll remind you that this is a legitmate forum to debate the shape of the earth and not a place to sling insults with wild abandon.

I hear a lot of glass breaking.

Quote from: Kendrick on August 15, 2012, 05:53:32 PM

Read Earth not a Globe.

Quote from: Samuel Birley Rowbotham

IF a theodolite is placed on the sea shore, "levelled," and directed towards the sea, the line of the horizon will be a given amount below the cross-hair, and a certain "dip" or inclination from the level position will have to be made to bring the cross-hair and the sea-horizon together. If the theodolite is similarly fixed, but at a greater altitude, the space between the cross-hair and the sea horizon, and the dip of the instrument to bring them together, is also greater.

Did you read the entire chapter?

Quote from: Samuel Birley Rowbotham

The author saw at once that this peculiarity depended upon the construction of the instruments. He ascertained that in those of the very best construction, and of the most perfect adjustment, there existed a certain degree of refraction, or, as it is called technically, "collimation," or a slight divergence of the rays of light from the axis of the eye, on passing through the several glasses of the theodolite. He therefore obtained an iron tube, about 18 inches in length; one end was closed, except a very small aperture in the centre; and at the other end cross-hairs were fixed. A spirit level was then attached, and the whole carefully adjusted. On directing it, from a considerable elevation, towards the sea,

p. 42

and looking through the small aperture at one end, the cross-hair at the opposite end was seen to fall to the horizon, as shown at fig. 31. This has been tried in various places, and at different altitudes, and always with the same result; showing clearly that the horizon visible below the cross-hair of an ordinary levelling instrument is the result of refraction, from looking through the various glasses of the telescope; for on looking through an instrument in every respect the same in construction, except being free from lenses, a different result is observed, and one precisely the same as that seen from a balloon, from any promontory, and in the experiment at Brighton, shown in fig. 27, p. 39.

These comparative experiments cannot fail to satisfy any unbiassed observer that in every levelling instrument where lenses are employed, there is, of necessity, more or less divergence of the line of sight from the true or normal axis; and that however small the amount--perhaps inappreciable in short lengths of observation--it is considerable in distances of several miles. Every scientific surveyor of experience is fully aware of this and other peculiarities in all such instruments, and is always ready to make allowances for them in important surveys. As a, still further proof of this behaviour of the telescopic levelling instruments, the following simple experiment may be tried. Select a piece of ground--a terrace, promenade, line of railway, or embankment, which shall be perfectly horizontal for, say, five hundred yards. Let a signal staff, 5 feet high, be erected at one end, and a theodolite or spirit level fixed and carefully adjusted to exactly the

p. 43

same altitude at the other end. The top of the signal will then be seen a little below the cross-hair, although it has the same actual altitude, and stands upon the same horizontal foundation. If the positions of the signal staff and the spirit level be then reversed, the same result will follow.

Dear Tom. I've already shown that Rowbotham is a hack here:

http://www.theflatearthsociety.org/forum/index.php/topic,55463.0.html#.UCx_jET5JFA

If you wish to use him as a valid source, I suggest you prove the points I've raised in the link wrong. If you are incapable of doing so, then let the record show that Rowbotham is an invalid source of accurate information.

I have shown that you are very bad at thinking logically here:

http://www.theflatearthsociety.org/forum/index.php/topic,18929.msg1380514/topicseen.html#msg1380514

I have also shown that you are very adept at  misunderstanding basic concepts earlier in this forum.

It seems when I bring up these points, you simply ignore them because you are intellectually incapable of doing anything else.

i was hoping jroa might make something other than a zero-content post for once, but what's dubious in that article is that the difference is too small to be seen with the naked eye in most cases, not that there's a difference.

The section markjo quoted does not contain any sources whatsoever.

I did - did I miss a part where he said the horizon actually does come up to the level-line in a levelled theodolite?  Because it appears to me that he's sheepishly attempting to explain it away.

You asked for a source that stated the horizon does not meet you at eye level when looking through a theodolite - you have one, I'm frankly surpised you werent aware of it.

I've read that section. I was curious what the source for TK's claim was. TK used the misaligned theodolite example as proof that the earth was a globe.

However, we've now learned from the source you quoted that the maligning of the theodolite is actually due to the refraction/convergence trough the lenses.

Dear Tom. I've already shown that Rowbotham is a hack here:

http://www.theflatearthsociety.org/forum/index.php/topic,55463.0.html#.UCx_jET5JFA

In that thread you have rubbish arguments like "the earth spins at a constant rate". You've apparently never heard of centripetal acceleration, which occurs when bodies rotate.

Well, I was really hoping this thread was dead. It seems as though it was not destined yet.

Quote from: Kendrick on August 15, 2012, 09:27:35 PM

I did - did I miss a part where he said the horizon actually does come up to the level-line in a levelled theodolite?  Because it appears to me that he's sheepishly attempting to explain it away.

You asked for a source that stated the horizon does not meet you at eye level when looking through a theodolite - you have one, I'm frankly surpised you werent aware of it.

I've read that section. I was curious what the source for TK's claim was. TK used the misaligned theodolite example as proof that the earth was a globe.

However, we've now learned from the source you quoted that the maligning of the theodolite is actually due to the refraction/convergence trough the lenses.

No. It's because the theolodite is level. Even if the ground was perfectly flat, the theolodite would always show the crosshairs above it.

In that thread you have rubbish arguments like "the earth spins at a constant rate". You've apparently never heard of centripetal acceleration, which occurs when bodies rotate.

You should do more reading before you try and use argument based on science, a topic you so readily attempt to discredit.

http://en.wikipedia.org/wiki/Centripetal_acceleration#Tangential_and_centripetal_acceleration

Almost the very first works in this piece are...

The velocity of a particle moving on a curved path...

That's just to give you an idea that you either do not know what you are talking about (which I highly suspect is true), or that you are intentionally mis-using names of things to try and make your point. Those equations in the article have nothing to do with the rotation of a body, they pertain to a particle moving in a curved path.

No. It's because the theolodite is level. Even if the ground was perfectly flat, the theolodite would always show the crosshairs above it.

Please provide a source for this.

Those equations in the article have nothing to do with the rotation of a body, they pertain to a particle moving in a curved path.

Rotation causes particles to move in curved paths, gumshoe.

Quote from: Thinking Man

No. It's because the theolodite is level. Even if the ground was perfectly flat, the theolodite would always show the crosshairs above it.

Please provide a source for this.

Is that really necessary? Perspective laws (which you love to muddle with so much) and physics (to do with light, you know, the stuff that would have to bend at an obscenely impossible angle for your idea to work) disagree with you, and are your source. Read... any physics book. Or read any art book. Why should I provide sources when you're just going to tell me what Rowbotham says?

Quote from: Thinking Man

Those equations in the article have nothing to do with the rotation of a body, they pertain to a particle moving in a curved path.

Rotation causes particles to move in curved paths, gumshoe.

Shall I define acceleration for you tom? It does not just mean speeding up. It is any change in velocity/vector in 3 dimensional space.

Is that really necessary? Perspective laws (which you love to muddle with so much) and physics (to do with light, you know, the stuff that would have to bend at an obscenely impossible angle for your idea to work) disagree with you, and are your source. Read... any physics book. Or read any art book. Why should I provide sources when you're just going to tell me what Rowbotham says?

Yes, a source is necessary. A google search of 'horizon eye level' brings up numerous sources which say that in perspective the horizon in the distance is always at eye level with the observer.

From Chapter 5 from the Perspective Handbook we read:

Horizon line and Eye level

Anyone who has ever been to the seaside will have seen a horizon (as long as it wasn't foggy). This is the line you see far away, out to sea. It's the line where the water stops and the sky starts. There are horizon lines everywhere, but usually you don't see them because something like a hill or a tree or a house is in the way.

You always see the horizon line at your eye level. In fact, if you change your eye level (by standing up, or sitting down) the horizon line changes too, and follows your eye level. Your eye level always follows you around everywhere because it's your eye level. If you sit on the floor the horizon is at your eye level. If you stand up, it's at your eye level. If you stand on top of a very tall building, or look out of the window of an aeroplane, the horizon is still at your eye level. It's only everything else that appears to change in relation to your eye level. The fact is, that everything looks the way it does from your point of view because you see it in relation to yourself. So if you are sitting looking out of the window of an airliner everything is going to look shorter than you because at this moment you are taller (or higher) than everything else.

Shall I define acceleration for you tom? It does not just mean speeding up. It is any change in velocity/vector in 3 dimensional space.

A change of velocity/vector occurs when bodies rotate.

Quote from: Kendrick on August 15, 2012, 09:27:35 PM

I did - did I miss a part where he said the horizon actually does come up to the level-line in a levelled theodolite?  Because it appears to me that he's sheepishly attempting to explain it away.

You asked for a source that stated the horizon does not meet you at eye level when looking through a theodolite - you have one, I'm frankly surpised you werent aware of it.

I've read that section. I was curious what the source for TK's claim was. TK used the misaligned theodolite example as proof that the earth was a globe.

However, we've now learned from the source you quoted that the maligning of the theodolite is actually due to the refraction/convergence trough the lenses.

Just so I'm sure - it seems like you actually maintaining Rowbotham's claim that all precision lensed instruments are 'misaligned' (your word).  Is this correct?

What about digital instruments - do they suffer the same malady? 

I've looked through a theodolite at the horizon to verify that it does not meet you at eye-level.  There are smart phone applications that will provide the same data.  Due to the overwhelming amount of empirical architectural evidence to the contrary I do not find Rowbothams assertion that all lensed instruments are inaccurate credible.

Quote from: Cat Earth Theory on August 15, 2012, 09:11:21 PM

i was hoping jroa might make something other than a zero-content post for once, but what's dubious in that article is that the difference is too small to be seen with the naked eye in most cases, not that there's a difference.

The section markjo quoted does not contain any sources whatsoever.

Quote from: Kendrick on August 15, 2012, 09:27:35 PM

I did - did I miss a part where he said the horizon actually does come up to the level-line in a levelled theodolite?  Because it appears to me that he's sheepishly attempting to explain it away.

You asked for a source that stated the horizon does not meet you at eye level when looking through a theodolite - you have one, I'm frankly surpised you werent aware of it.

I've read that section. I was curious what the source for TK's claim was. TK used the misaligned theodolite example as proof that the earth was a globe.

However, we've now learned from the source you quoted that the maligning of the theodolite is actually due to the refraction/convergence trough the lenses.

Quote from: Megaman on August 15, 2012, 10:15:37 PM

Dear Tom. I've already shown that Rowbotham is a hack here:

http://www.theflatearthsociety.org/forum/index.php/topic,55463.0.html#.UCx_jET5JFA

In that thread you have rubbish arguments like "the earth spins at a constant rate". You've apparently never heard of centripetal acceleration, which occurs when bodies rotate.

First off, at the beginning of that thread I bring up 3 simple points that do not use centripetal acceleration to prove some of Rowbotham's flaws. Centripetal acceleration isn't mentioned in those.

I am willing to bet that you are incapable of refuting any of the 3 points.


As for centripetal acceleration, I believe you don't know what it actually is.

Your statement seems to be implying that "Centripetal acceleration exists, therefore the body in question can not be rotating at a constant rate."

Yet you state that all rotating bodies exhibit centripetal acceleration.

This means that centripetal acceleration exists even if the body is rotating at a constant rate. (i.e. has a constant tangential or angular velocity).

Please look things up Tom.

It is entirely possible for things to rotate at a constant rate.

All rotating objects exhibit centripetal acceleration.

Therefore an object rotating at a constant rate still exhibits centripetal acceleration.

The presence of centripetal acceleration does not prove that the rotation is not periodic.


I tried to enlighten you in other posts. Lets recap, shall we?

Quote from: Tom Bishop on January 08, 2008, 09:48:02 AM

Quote

Everything is relative.  People had very similar problems coming to grips with dropping stuff on a round rotating Earth.  Shouldn't things whril around at the speed of the Earth's rotation as soon as you release them?  A good analogy used was to imagine dropping a weight from the mast of a sailing ship.  No matter whether the ship was moving or not the weight would still hit the deck right under you.  Of course, this is using a RE argument backwards, but no matter.

That would only work if the earth was rotating at a constant speed. But a rotating body cannot move at a constant speed since rotating bodies exhibit centripetal acceleration.

I see. So you just don't understand how things work.

1). Centripetal acceleration always points toward the center of the rotating body.

2.) Centripetal acceleration = [(Tangental velocity)^2]/radius.

If you understood math, you'd know that a round Earth actually allows it to be analogous to the ship experiment because when you move north or south, the radius increases or decrease with tangential velocity.

Also, Earth's rotation speed is, in the scope of these calculations, essentially constant.

I think reading too much Rowbotham has damaged you're approach to logic.

Quote from: Tom Bishop on January 08, 2008, 10:06:20 AM

Quote

so what makes you think earth's rotation is not constant?
since you are the first person to say that, the burden of proof is entirely on YOU!

ALL rotating bodies exhibit centripetal acceleration. Acceleration occurs when there is a the rate of change of tangential velocity. By definition a rotating body cannot move at a constant speed. To calculate a centripetal or radial acceleration we can use the formula w^2*r or v^2/r.

http://theory.uwinnipeg.ca/physics/circ/node6.html

When you're spinning around on a merry-go-round which is moving at a "constant" 10 miles per hour and let go, what happens?

The direction of the centripetal acceleration is always inwards along the radius vector of the circular motion.

The experiment is only concerned with tangential tangential velocity, which is constant.

Please think about things before you post them.

Quote from: Tom Bishop on January 08, 2008, 10:15:06 AM

Quote from: eric bloedow on January 08, 2008, 10:10:02 AM

you would fly off

So do you agree that rotating bodies exhibit acceleration?

The acceleration forces of rotating bodies are orthogonal to tangential velocity of the rotating body. Also, if you actually understood rotating body acceleration you'd know that when something moves in a circular path, with a constant radius, it does so because centrifugal and centripetal acceleration are canceling each other out.

I challenge you Tom.

4 simple points. 3 regarding Rowbotham's chapter on tides.

1 regarding the ability of a body to rotate at a constant rate (i.e. have a constant tangential and angular velocity) and still exhibit centripetal acceleration.

Refute these 4 points. Any of them.

I'm willing to bet you are incapable of doing so.

Quote from: ThinkingMan on August 16, 2012, 07:31:22 AM

Is that really necessary? Perspective laws (which you love to muddle with so much) and physics (to do with light, you know, the stuff that would have to bend at an obscenely impossible angle for your idea to work) disagree with you, and are your source. Read... any physics book. Or read any art book. Why should I provide sources when you're just going to tell me what Rowbotham says?

Yes, a source is necessary. A google search of 'horizon eye level' brings up numerous sources which say that in perspective the horizon in the distance is always at eye level with the observer.

From Chapter 5 from the Perspective Handbook we read:

Horizon line and Eye level

Anyone who has ever been to the seaside will have seen a horizon (as long as it wasn't foggy). This is the line you see far away, out to sea. It's the line where the water stops and the sky starts. There are horizon lines everywhere, but usually you don't see them because something like a hill or a tree or a house is in the way.

You always see the horizon line at your eye level. In fact, if you change your eye level (by standing up, or sitting down) the horizon line changes too, and follows your eye level. Your eye level always follows you around everywhere because it's your eye level. If you sit on the floor the horizon is at your eye level. If you stand up, it's at your eye level. If you stand on top of a very tall building, or look out of the window of an aeroplane, the horizon is still at your eye level. It's only everything else that appears to change in relation to your eye level. The fact is, that everything looks the way it does from your point of view because you see it in relation to yourself. So if you are sitting looking out of the window of an airliner everything is going to look shorter than you because at this moment you are taller (or higher) than everything else.

This does not say, nor does it mean, that the horizon is actually at eye level. It appears to be... to the unaided eye. A device such as a theolodite shows that perspective is a flawed view of reality. Admit it, Rowbotham was wrong, and is a fool.

Quote from: ThinkingMan

Shall I define acceleration for you tom? It does not just mean speeding up. It is any change in velocity/vector in 3 dimensional space.

A change of velocity/vector occurs when bodies rotate.

Which does not mean that the Earth does not rotate at a constant speed. You can't weasel your way out of it by agreeing with what I said and attempting to confuse and derail to debate.

Quote from: Tom Bishop on August 16, 2012, 03:41:54 AM

Quote from: Kendrick on August 15, 2012, 09:27:35 PM

I did - did I miss a part where he said the horizon actually does come up to the level-line in a levelled theodolite?  Because it appears to me that he's sheepishly attempting to explain it away.

You asked for a source that stated the horizon does not meet you at eye level when looking through a theodolite - you have one, I'm frankly surpised you werent aware of it.

I've read that section. I was curious what the source for TK's claim was. TK used the misaligned theodolite example as proof that the earth was a globe.

However, we've now learned from the source you quoted that the maligning of the theodolite is actually due to the refraction/convergence trough the lenses.

Just so I'm sure - it seems like you actually maintaining Rowbotham's claim that all precision lensed instruments are 'misaligned' (your word).  Is this correct?

What about digital instruments - do they suffer the same malady? 

I've looked through a theodolite at the horizon to verify that it does not meet you at eye-level.  There are smart phone applications that will provide the same data.  Due to the overwhelming amount of empirical architectural evidence to the contrary I do not find Rowbothams assertion that all lensed instruments are inaccurate credible.

This is correct. If lensed instruments were severely distorted in one way, they would also be distorted in others. No double standards, Tom.

From Chapter 5 from the Perspective Handbook we read:

Horizon line and Eye level

Anyone who has ever been to the seaside will have seen a horizon (as long as it wasn't foggy). This is the line you see far away, out to sea. It's the line where the water stops and the sky starts. There are horizon lines everywhere, but usually you don't see them because something like a hill or a tree or a house is in the way.

You always see the horizon line at your eye level. In fact, if you change your eye level (by standing up, or sitting down) the horizon line changes too, and follows your eye level. Your eye level always follows you around everywhere because it's your eye level. If you sit on the floor the horizon is at your eye level. If you stand up, it's at your eye level. If you stand on top of a very tall building, or look out of the window of an aeroplane, the horizon is still at your eye level. It's only everything else that appears to change in relation to your eye level. The fact is, that everything looks the way it does from your point of view because you see it in relation to yourself. So if you are sitting looking out of the window of an airliner everything is going to look shorter than you because at this moment you are taller (or higher) than everything else.

Totally misapplied quote. How often do we hear FE'ers shriek that Newtonian mechanics are "wrong" and therefore should not be used? This is a good analogy to that. This description of the horizon at eye level is perfectly good enough for the naked eye in everyday situations. It is, however, inaccurate when it comes to things like magnified views through theodolites and telescopes.

[
From Chapter 5 from the Perspective Handbook we read:

As usual, Tom Bishop tries to mix Physics with Drawing Techniques!

The complete name of the book he quotes is "Perspective Drawing Handbook"! Nobody cares whether your horizon gets drawn a millimeter too high or a millimeter too low in a drawing you are making. Drawings are not photographs and in many cases you will, in fact, do a better drawing if it does not mimic reality as well as photographs do!

The very fact that people still do drawings instead of taking photographs is because drawings exaggerate, twist, delineate or otherwise accentuate desired aspects of the image. Drawings are not photographs and Drawing Techniques are not Physics.

And vanishing points are part of a drawing technique, not of a Physics model.

Quote from: Tom Bishop on August 16, 2012, 07:58:25 AM

[
From Chapter 5 from the Perspective Handbook we read:

As usual, Tom Bishop tries to mix Physics with Drawing Techniques!

The complete name of the book he quotes is "Perspective Drawing Handbook"! Nobody cares whether your horizon gets drawn a millimeter too high or a millimeter too low in a drawing you are making. Drawings are not photographs and in many cases you will, in fact, do a better drawing if it does not mimic reality as well as photographs do!

The very fact that people still do drawings instead of taking photographs is because drawings exaggerate, twist, delineate or otherwise accentuate desired aspects of the image. Drawings are not photographs and Drawing Techniques are not Physics.

And vanishing points are part of a drawing technique, not of a Physics model.

He is making Robotham's mistake: confusing horizon and vanishing point.

Quote from: trig on August 16, 2012, 12:33:39 PM

Quote from: Tom Bishop on August 16, 2012, 07:58:25 AM

[
From Chapter 5 from the Perspective Handbook we read:

As usual, Tom Bishop tries to mix Physics with Drawing Techniques!

The complete name of the book he quotes is "Perspective Drawing Handbook"! Nobody cares whether your horizon gets drawn a millimeter too high or a millimeter too low in a drawing you are making. Drawings are not photographs and in many cases you will, in fact, do a better drawing if it does not mimic reality as well as photographs do!

The very fact that people still do drawings instead of taking photographs is because drawings exaggerate, twist, delineate or otherwise accentuate desired aspects of the image. Drawings are not photographs and Drawing Techniques are not Physics.

And vanishing points are part of a drawing technique, not of a Physics model.

He is making Robotham's mistake: confusing horizon and vanishing point.

That's an easy thing to confuse to the ignorant, uneducated mind.