Flat earth vs Round Earth directional navigation

Ok, so I have a question. I have been thinking about what Jroa has been telling me and I really don't get it. I have no back ground in physics in fact I have no college at all just my training in navigation, seamanship, and coxswain so if this is about physics don't freak about and say I am dumb or something. My years of training in navigation have taught me many things about Earth and most of it I don't understand I just know that IF I do X and do the math then Y happens and so on (more complicated just keeping it simple).

Here is a picture I made excuse the amazing boat drawing skills that you all wish you had.




Now in figure 1. That is a boat traveling at a 270 true course, you can tell that boat is traveling west because it is heading in that direction, following the Earths curve and of course not exactly in a straight line path (rhumb line, great circle so on depending on what the vessel is doing exactly) that vessel will meet a piece of land at some point staying at 270. You can see that the vessel is really going in that direction, not making course changes and not turning.

now in figure 2. that is what the vessel would be doing on a flat Earth. The vessel is apparently traveling at 270 true. The funny thing is that the vessel is going to travel in a circle. How can that vessel be doing 270 true heading west, yet doing a circle? On a spherical Earth the vessel can of course do 270 true heading west following the curve and not be doing an actual circle (minus the one it is doing following earths curve)

take a basketball and put one of the lines parellel to the deck and imagine you are on that black line walking it going west. You will be traveling west (in a broad circle, but that is because the ball is round!) Now take that ball pop it and lay it as flat as possible. Imagine you are on that same line walking west. You are now walking west, then north, then East, then south, and eventually coming back to where you started. So can you say that you were traveling at 270 the whole time around that flat ball?

So that is my problem, I know that I can travel at 270 and head west the whole time and end up back where I started due to the Earth being a sphere. On a flat Earth I would do an exact circle starting at 270, but then having to go 360 degrees slowly turning. It just makes no sense. I have tried uploading the flat Earth map on my Voyager program and chart a course at 270 and it takes the track leg's off of the map itself. you cannot do 270 on a flat earth... unless someone makes a flat Earth chart I do not see how you can plot a course anywhere on a flat Earth.

Don't you already know the answer you're going to get? "well in both models, you're traveling in a circle, wouldn't it be easy to get confused between which one was real?" or maybe "well the magnetic pole will make you think you're traveling in a straight line". Probably something clever like that. Let's watch and see O.O

Don't you already know the answer you're going to get? "well in both models, you're traveling in a circle, wouldn't it be easy to get confused between which one was real?" or maybe "well the magnetic pole will make you think you're traveling in a straight line". Probably something clever like that. Let's watch and see O.O

I really wish I can explain this better. I hope people understand what I am trying to say. According to flat Earth theory you move in a circle, the problem is that on a flat pice of land moving in a circle means you are slowly turning in a circle and a magnetic compass along with your ships gyro would show this. On a sphere you can move in a circle while maintaining a set direction, such as west. Your ships gyro will stay at 270 as you move along the Earths curve. Your ships magnetic compass would change, but in a predictable way and should always show 270 or around 270 after factoring in variation and deviation.

Well... the compass wouldn't change if the magnetic pole is somehow still magically at the... center? But a gyro wouldn't work properly on a flat earth.

I'm not sure how a gyro would need to be calibrated to work on a flat Earth. I guess it just would not work since you would not really need it to be a gyro, just a flat thing that can measure your exact heading.

The thing about the gyro and why it is so important is that it keeps you on your true heading factoring in the curve of the Earth (hence why it needs to be a gyro and calibrated accordingly) So I guess in the end you are 100% correct it would not work on a flat Earth.

They use gyros on space craft as well. It requires gravity to work properly as well, does it not?

Quote from: ThinkingMan on July 13, 2012, 01:33:16 PM

Don't you already know the answer you're going to get? "well in both models, you're traveling in a circle, wouldn't it be easy to get confused between which one was real?" or maybe "well the magnetic pole will make you think you're traveling in a straight line". Probably something clever like that. Let's watch and see O.O

I really wish I can explain this better. I hope people understand what I am trying to say. According to flat Earth theory you move in a circle, the problem is that on a flat pice of land moving in a circle means you are slowly turning in a circle and a magnetic compass along with your ships gyro would show this. On a sphere you can move in a circle while maintaining a set direction, such as west. Your ships gyro will stay at 270 as you move along the Earths curve. Your ships magnetic compass would change, but in a predictable way and should always show 270 or around 270 after factoring in variation and deviation.

On a sphere, except at the equator, when traveling due west or east you are turning in a circle too.  It's true in FET and RET.  Due west and due east on a round Earth are not straight lines (again, except at the equator).

Note that I think I understand your question but I'm kinda tired so if I'm wrong I apologize.

would your boat detect such a slight turn on a flat earth? its a very small small change. much like the fact that the earth appears flat.

i feel this will be the same as the discussion on gravity where both parties can not prove either way.

@Thinkingman,
Yes gyro's require gravity to work as intended. I think that UA might cover that as well (note that I do not believe in UA, but it mimics gravity) maybe someone with some knowledge in that stuff can answer if UA would have an adverse affect on a gyro.

@Roundy
You are correct, if I was to do a 090 true heading at say 89.00.00 N I would be doing a more prominent circle. The problem is that I am still on a sphere and would stay at a easterly heading, round and round and round as I go because I am not standing on on top of the world so to speak (I mean not traveling as if I am starring at the sphere, but I am on the sphere walking around it). At 89.00.00 N on a flat Earth I would be doing a circle on a flat horizontal piece ofl and and constantly turning as to not head off to the mythical ice wall.



So wich one is correct on the Flat Earth figure. Is it 1. or 2. ??  the 2. is a 270 west heading that would take you straight to the ice wall. The 1. one is the circular path that is suposed to happen on a flat Earth when heading in a direction. The problem still stands that on a sphere I can and am able to continue on a set heading and travel in the circle around Earth without having to go in any other direction. On the Flat Earth if I use the 2. then I hit and ice wall. If I use 1. then I am now locked in a circle like walking around the room I am in and have to change my heading to maintain the path I wish to travel.

If we are talking about heading in a circle at such a degree of longitude say... 89.99.99 then I can probably say I would notice the change in heading since you are now on the top of a sphere much like walking around the top of a hill. The problem is that you would feel that at all times on a flat Earth since there is no spherical piece in wich you can travel on. You are always horizontal to the land going round and round. I hope I am explaining the problem in my head well enough for people ot understand my questions.

in both models if you were traveling round the north pole you would be traveling in a circle. like roundy said, only at the equator are you traveling in the strait line.

it is said that if you walk in a strait line with no objects of reference you would actually walk in a big circle because one leg is stronger than the other. you wouldnt notice this circle. so if you follow a course with a compass on a flat earth do yuo think you would really notice the circle?

in both models if you were traveling round the north pole you would be traveling in a circle. like roundy said, only at the equator are you traveling in the strait line.

it is said that if you walk in a strait line with no objects of reference you would actually walk in a big circle because one leg is stronger than the other. you wouldnt notice this circle. so if you follow a course with a compass on a flat earth do yuo think you would really notice the circle?

Think about viewing a boat on a flat Earth from above. You know that the boat going to be at a heading of 090 true making way East at a longitude of 70.00.00N Do you think that you will see the vessel travel in that general direction (east) or do you think that the vessel will start to make a circle? If the vessel is then making a circle around a flat Earth do you think that you would see the vessel still moving in a easterly direction?

Now do the same thing on a sphere. Imagine you viewing a vessel making way easterly at 090 true starting at longitude 70.00.00N. That vessel is going to make a circle yes? as you watch that vessel travel around the sphere do you think that the vessel is having to change heading to complete the circle around the sphere? Now do you think that putting the vessel at any other longitude other then 85.00.00N/s + would change anything?

What I am trying to understand and possibly show and get some feedback on is the position of objects on a sphere vs a flat plane. I do understand that the circle around a sphere is not exactly straight due to the curve of Earth (rhumb line, giant circle is what we use in navigation, but not always as it makes simple track lines pretty complex and gives me a headache!)

On a flat plane you are always standing parellel to the deck so traveling in a circle is going to require multiple headings. On a sphere you are standing parellel to a sphere so as you travel in one direction you can make a circle around it without changing your heading. So my conclusion is that the notion of heading either east or west and never changing heading and inherently making a circle around the flat Earth can not be possible. Your ships gyro would detect your movement away from that heading. You cannot travel from california to japan going due west on a flat Earth... You have to change heading.

gosh I really am sorry if I am overcomplicating this concept or portraying my thoughts in an awkward/hard to understand way. I feel like this is more simple then what I am thinking, but that damned light bulb in my head seems to be flickering, but not staying on.

I understand what you are saying Boatswain, it's truly an interesting conundrum to contemplate. I will dedicate some time to thinking about this.

On a sphere you are standing parellel to a sphere so as you travel in one direction you can make a circle around it without changing your heading.

Stand twenty feet south of the north pole. Head west. How long are you still headed west if you walk in a straight line? Now thirty feet. How long? Now 60 feet. Extrapolate. "West" is not a straight line. One cannot head "west" without changing one's heading on a sphere or flat earth.

So my conclusion is that the notion of heading either east or west and never changing heading and inherently making a circle around the flat Earth can not be possible.

Well, you're right. But neither would it be possible on a globe saving at the equator.

You cannot travel from california to japan going due west on a flat Earth... You have to change heading.

As you would on a globe.

Quote from: BoatswainsMate on July 13, 2012, 11:10:23 PM

On a sphere you are standing parellel to a sphere so as you travel in one direction you can make a circle around it without changing your heading.

Stand twenty feet south of the north pole. Head west. How long are you still headed west if you walk in a straight line? Now thirty feet. How long? Now 60 feet. Extrapolate. "West" is not a straight line. One cannot head "west" without changing one's heading on a sphere or flat earth.

Such a short distance it would not matter. Think bigger. Short distances are tricky. walking west from the north pole you would begin to move in a giant circle curve eventually coming to a direct west when you reach near the 0 degree mark I would think.

So my conclusion is that the notion of heading either east or west and never changing heading and inherently making a circle around the flat Earth can not be possible.
Well, you're right. But neither would it be possible on a globe saving at the equator.

It is possible on a globe, I do did it on almost every patrol on the pacific. I guarantee you I can make a series of legs ranging from 280 then gradually coming to somewhere around 235 and I can get across the pacific. I am not saying that it is impossible to go west on the Flat Earth, just that doing so would make you hit the ice-wall/edge/whatever is there. My problem is that the circle that you supposedly make on the flat Earth is not possible, to me.

You cannot travel from california to japan going due west on a flat Earth... You have to change heading.

As you would on a globe.[/quote]
False. I really wish I had a scanner... I have so many charts that have been used by my previous ships to travel across the pacific and end in Japan using headings ranging from 210-300. All of wich are westerly headings. Sure a little north/west or south/west, but I know a straight line is not going to work. If it did work hell my job would be so easy.. one leg 258 true from San Fran to Mito... done hahaaha (258 is a rough estimate)

with all that said, I really do not want to argue straight lines. I know exact straight lines are not possible. I want to know why On a flat Earth following any longitud mark it shows you traveling in a circle... while apparently maintaining a heading and not changing that heading to change general direction (north,south,east,west) impossible.

well ski, I think I sounded a little confusing. The damn Carlo got to me... those jugs are so tempting. By heading I really ment to say general direction (north, south, east, west) And once again I am sorry if I am just not asking the right way or explaining my problem horribly.

I understand what you are saying Boatswain, it's truly an interesting conundrum to contemplate. I will dedicate some time to thinking about this.

Thanks Pongo, this is really racking my brain.

I double posted, I'm sorry.

Quote from: squevil on July 13, 2012, 08:49:30 PM

in both models if you were traveling round the north pole you would be traveling in a circle. like roundy said, only at the equator are you traveling in the strait line.

it is said that if you walk in a strait line with no objects of reference you would actually walk in a big circle because one leg is stronger than the other. you wouldnt notice this circle. so if you follow a course with a compass on a flat earth do yuo think you would really notice the circle?

Think about viewing a boat on a flat Earth from above. You know that the boat going to be at a heading of 090 true making way East at a longitude of 70.00.00N Do you think that you will see the vessel travel in that general direction (east) or do you think that the vessel will start to make a circle? If the vessel is then making a circle around a flat Earth do you think that you would see the vessel still moving in a easterly direction?

Now do the same thing on a sphere. Imagine you viewing a vessel making way easterly at 090 true starting at longitude 70.00.00N. That vessel is going to make a circle yes? as you watch that vessel travel around the sphere do you think that the vessel is having to change heading to complete the circle around the sphere? Now do you think that putting the vessel at any other longitude other then 85.00.00N/s + would change anything?

What I am trying to understand and possibly show and get some feedback on is the position of objects on a sphere vs a flat plane. I do understand that the circle around a sphere is not exactly straight due to the curve of Earth (rhumb line, giant circle is what we use in navigation, but not always as it makes simple track lines pretty complex and gives me a headache!)

On a flat plane you are always standing parellel to the deck so traveling in a circle is going to require multiple headings. On a sphere you are standing parellel to a sphere so as you travel in one direction you can make a circle around it without changing your heading. So my conclusion is that the notion of heading either east or west and never changing heading and inherently making a circle around the flat Earth can not be possible. Your ships gyro would detect your movement away from that heading. You cannot travel from california to japan going due west on a flat Earth... You have to change heading.

gosh I really am sorry if I am overcomplicating this concept or portraying my thoughts in an awkward/hard to understand way. I feel like this is more simple then what I am thinking, but that damned light bulb in my head seems to be flickering, but not staying on.

this made more sense to me and i just woke up! i still find it hard to imagine that you would detect such a circle. its so large you just wouldnt notice anything. i doubt you gyro would be made sensitive enough to detect it either.

Im happy that made a little more sense Squevil! So on a sphere your gyro does detect a slight arc like motion so we correct for deviation. Every ship has a deviation table that is updated periodically to help us know our true heading. I wish I could find a course change log to show you, but basically the areas to fill out on it are Time, Ships position, speed, current deviation, variation, true heading, and magnetic heading. So on board we do account for the curve we travel on to correct our heading to maintain a course we want.

now what is seriously boggling my mind is that on a sphere the path we travel is not exactly a prominent curve as we circle around the Earth. On a flat Earth the circle that you would do is considerably greater because you are not on a sphere anymore you are on a flat plane. It is walking around a sphere vs walking in a circle around a flat plane. The two shapes cause different affects.

You walk around a sphere to make the circle. You cannot do that same on a flat plane. A flat plane circle is just like walking in a circle on any flat area, you walk north, then east, south, and west to create the 360 degree rotation. You have to move in that way to make a circle on a flat plane, I do not know of any other way aside from going under the flat plane then back up it to make the circle you would do comparatively to a sphere. That is my dilemma. It is simply how you are positioned on a sphere compared to a flat plane.

You walk around a sphere to make the circle. You cannot do that same on a flat plane. A flat plane circle is just like walking in a circle on any flat area, you walk north, then east, south, and west to create the 360 degree rotation. You have to move in that way to make a circle on a flat plane, I do not know of any other way aside from going under the flat plane then back up it to make the circle you would do comparatively to a sphere. That is my dilemma.

No.  On a flat Earth go due east and you are walking in a circle.  There's no walking north then east then south then west.  The path is curved but it's still one direction.  Go in one direction, travel in a circle, end up back where you started.  Exactly the same as in RE.  There's no change in heading.  Unless I'm missing something you still seem to be having trouble grasping this?

Quote from: BoatswainsMate on July 14, 2012, 08:16:28 AM

You walk around a sphere to make the circle. You cannot do that same on a flat plane. A flat plane circle is just like walking in a circle on any flat area, you walk north, then east, south, and west to create the 360 degree rotation. You have to move in that way to make a circle on a flat plane, I do not know of any other way aside from going under the flat plane then back up it to make the circle you would do comparatively to a sphere. That is my dilemma.

No.  On a flat Earth go due east and you are walking in a circle.  There's no walking north then east then south then west.  The path is curved but it's still one direction.  Go in one direction, travel in a circle, end up back where you started.  Exactly the same as in RE.  There's no change in heading.  Unless I'm missing something you still seem to be having trouble grasping this?

It has to be demonstrated that on a flat Earth if you head constantly East for instance you are doing a circle. It contradicts all modern instruments.

And saying "Exactly the same as in RE" is a complete misunderstanding of a cpndescending guy saying "Unless I'm missing something you still seem to be having trouble grasping this?"


And saying

Quote from: BoatswainsMate on July 14, 2012, 08:16:28 AM

You walk around a sphere to make the circle. You cannot do that same on a flat plane. A flat plane circle is just like walking in a circle on any flat area, you walk north, then east, south, and west to create the 360 degree rotation. You have to move in that way to make a circle on a flat plane, I do not know of any other way aside from going under the flat plane then back up it to make the circle you would do comparatively to a sphere. That is my dilemma.

No.  On a flat Earth go due east and you are walking in a circle.  There's no walking north then east then south then west.  The path is curved but it's still one direction.  Go in one direction, travel in a circle, end up back where you started.  Exactly the same as in RE.  There's no change in heading.  Unless I'm missing something you still seem to be having trouble grasping this?

Well there might be some physics involved that I do not understand. Why, if I walk East, on a flat plane do I go in a circle? What is causing me to move in a circular path on a flat plane? I understand why on a sphere if I head East I can go in a circle around the sphere, but I am not going around the flat plane I am heading in a easterly direction. On a sphere you do not move in a straight line because the sphere is curved and you have to account for the affects oh the sphere on you in wich you travel in a arc like or great circle path. So you will always be heading east, but of course not exactly East wich is why ships need a deviation and variation table along with their gyro to maintain the direction that want to travel in.

It is basically the whole, how I view what an objects does on a sphere vs a flat plane. If you are looking down on a flat plane and you know that an object is moving in a easterly direction, why would I ever see it move in a circle? If you are watching that object that is suposed to be heading east go in a circle then why on Earth would you still think it is heading east? would you not believe that the object moving in that circle is heading a little south, then west, and then north to complete that circle on the flat plane? On a sphere watching an object move east you can watch it move around the sphere still heading east and come out from the back side of the sphere and complete 360 degrees around the sphere. The object would not head north or south or any other direction, but east.

So what is causing that vessel on a flat plane to travel in a circle without changing it's general direction from east?

I have countless times traveled across the pacific heading west, I can guarantee you that the vessel I was navigating did not go due north or due south to get across the pacific. Every instrument I have at my disposal has showed me that we headed in a westerly direction the whole patrol. When I say westerly direction I do mean we went south west and north west at times, but still westerly. I understand you do not travel in straight lines, I am not arguing that you do, but making a circle on a flat plane while only heading in one general direction is giving me a headache. It just does not add up, the affects of a sphere rotating on it's axis are completely different that that of a flat plane accelerating. Where is the curve on the flat plane that would cause either a rhumb line or great circle affect? Sure looking down on a sphere an object is traveling in a circle, the problem is that on a sphere you are able to head in a general direction while still doing that circle, on a flat plane heading in one general direction how in the world would you travel in a circle?

you guys have got this wrong. the fes has a strong point here. i said at the start that you cant prove it either way.
now remember the point about only walking 20 feet from the pole and you walk in a circle? well you said in a greater distance its different. well its not, the only difference is that the circle is sooo big you wouldnt notice it. now we have established that you will turn on a round earth now understand that if a ship sailed from liverpool to new york it wouldnt even notice the curve.

now here is a thought experiment;
take a ship with sensitive enough equipment to detect this curve. measure it at 20 degrees north and then at 20 degrees south over a length of say 200 miles. if both curves match you have a round earth. however if the southern curve is flatter then so is the earth (flat that is).

Well there might be some physics involved that I do not understand. Why, if I walk East, on a flat plane do I go in a circle? What is causing me to move in a circular path on a flat plane?

It's because of how we define "east" and "west".  They are always oriented to the north pole, which is in the center in FE and at the top in RE.  If you orient yourself east using a compass you are orienting yourself at a 90 degree angle in reference to the north pole.  If you were to travel in a perfectly straight line from that point, you would not be traveling due east, you'd be veering toward the south.  If you picture the Earth as a disk, with the north pole in the center and the south at the edges, this should be pretty easy to see.  Keep going due east, on the other hand, and you travel the arc of a circle, just like in RE.

Also I think squevil is right on the money with his point.  In FE the curve just keeps getting flatter and flatter the further south you start your journey due east.  In RE it straightens out when you reach the equator, and then the curve starts getting more pronounced as your starting point goes more and more to the south.

Quote from: BoatswainsMate on July 14, 2012, 08:48:13 AM

Well there might be some physics involved that I do not understand. Why, if I walk East, on a flat plane do I go in a circle? What is causing me to move in a circular path on a flat plane?

It's because of how we define "east" and "west".  They are always oriented to the north pole, which is in the center in FE and at the top in RE.  If you orient yourself east using a compass you are orienting yourself at a 90 degree angle in reference to the north pole.  If you were to travel in a perfectly straight line from that point, you would not be traveling due east, you'd be veering toward the south.  If you picture the Earth as a disk, with the north pole in the center and the south at the edges, this should be pretty easy to see.  Keep going due east, on the other hand, and you travel the arc of a circle, just like in RE.

Also I think squevil is right on the money with his point.  In FE the curve just keeps getting flatter and flatter the further south you start your journey due east.  In RE it straightens out when you reach the equator, and then the curve starts getting more pronounced as your starting point goes more and more to the south.

if there was a line that marked the path on a sphere the boat would follow it without going starboard or port etc, on a circle it would curve away from you, boats would follow this and feel this curving as a slight force, toward either starboard or port (very slight, but it is testable), on one side of the boat, this would not happen on a sphere.

Quote from: Roundy the Truthinessist on July 14, 2012, 09:19:42 AM

Quote from: BoatswainsMate on July 14, 2012, 08:48:13 AM

Well there might be some physics involved that I do not understand. Why, if I walk East, on a flat plane do I go in a circle? What is causing me to move in a circular path on a flat plane?

It's because of how we define "east" and "west".  They are always oriented to the north pole, which is in the center in FE and at the top in RE.  If you orient yourself east using a compass you are orienting yourself at a 90 degree angle in reference to the north pole.  If you were to travel in a perfectly straight line from that point, you would not be traveling due east, you'd be veering toward the south.  If you picture the Earth as a disk, with the north pole in the center and the south at the edges, this should be pretty easy to see.  Keep going due east, on the other hand, and you travel the arc of a circle, just like in RE.

Also I think squevil is right on the money with his point.  In FE the curve just keeps getting flatter and flatter the further south you start your journey due east.  In RE it straightens out when you reach the equator, and then the curve starts getting more pronounced as your starting point goes more and more to the south.

if there was a line that marked the path on a sphere the boat would follow it without going starboard or port etc

This is where you're mistaken.  The only place a boat travels in a due east or west direction and travels in a straight line is at the equator.  Everywhere else, there'd be that slight curving to port or starboard.

Quote from: burt on July 14, 2012, 09:30:53 AM

Quote from: Roundy the Truthinessist on July 14, 2012, 09:19:42 AM

Quote from: BoatswainsMate on July 14, 2012, 08:48:13 AM

Well there might be some physics involved that I do not understand. Why, if I walk East, on a flat plane do I go in a circle? What is causing me to move in a circular path on a flat plane?

It's because of how we define "east" and "west".  They are always oriented to the north pole, which is in the center in FE and at the top in RE.  If you orient yourself east using a compass you are orienting yourself at a 90 degree angle in reference to the north pole.  If you were to travel in a perfectly straight line from that point, you would not be traveling due east, you'd be veering toward the south.  If you picture the Earth as a disk, with the north pole in the center and the south at the edges, this should be pretty easy to see.  Keep going due east, on the other hand, and you travel the arc of a circle, just like in RE.

Also I think squevil is right on the money with his point.  In FE the curve just keeps getting flatter and flatter the further south you start your journey due east.  In RE it straightens out when you reach the equator, and then the curve starts getting more pronounced as your starting point goes more and more to the south.

if there was a line that marked the path on a sphere the boat would follow it without going starboard or port etc

This is where you're mistaken.  The only place a boat travels in a due east or west direction and travels in a straight line is at the equator.  Everywhere else, there'd be that slight curving to port or starboard.

the ark I am talking about is one that bisects a sphere (usually called a great circle), you can have bisections anywhere on a spehere (not just at the equator); what you are talking about is not a great circle, but a circle that runs parralell to a great circle (in this case the equator).

Quote from: Roundy the Truthinessist on July 14, 2012, 09:39:32 AM

Quote from: burt on July 14, 2012, 09:30:53 AM

Quote from: Roundy the Truthinessist on July 14, 2012, 09:19:42 AM

Quote from: BoatswainsMate on July 14, 2012, 08:48:13 AM

Well there might be some physics involved that I do not understand. Why, if I walk East, on a flat plane do I go in a circle? What is causing me to move in a circular path on a flat plane?

It's because of how we define "east" and "west".  They are always oriented to the north pole, which is in the center in FE and at the top in RE.  If you orient yourself east using a compass you are orienting yourself at a 90 degree angle in reference to the north pole.  If you were to travel in a perfectly straight line from that point, you would not be traveling due east, you'd be veering toward the south.  If you picture the Earth as a disk, with the north pole in the center and the south at the edges, this should be pretty easy to see.  Keep going due east, on the other hand, and you travel the arc of a circle, just like in RE.

Also I think squevil is right on the money with his point.  In FE the curve just keeps getting flatter and flatter the further south you start your journey due east.  In RE it straightens out when you reach the equator, and then the curve starts getting more pronounced as your starting point goes more and more to the south.

if there was a line that marked the path on a sphere the boat would follow it without going starboard or port etc

This is where you're mistaken.  The only place a boat travels in a due east or west direction and travels in a straight line is at the equator.  Everywhere else, there'd be that slight curving to port or starboard.

the ark I am talking about is one that bisects a circle (usually called a great circle), you can have bisections anywhere (not just at the equator); what you are talking about is not a great circle, but a circle that runs parralell to a great circle (in this case the equator).

The only great circle that follows a due east or west path in RE is the equator.

Immaterial, any bisection of a sphere travelled, that is measured with a compass, would be compensated for. it can still be tested.

This would be evern more obvious on a aeroplane.

Immaterial

No it's not.  This entire thread we have been discussing due east and west courses.  Your response was explicitly to an example of following such a course.

I think if you are sailing near the equator, your course would need 8" per mile of correction to keep due east or west. That would be using Rowbotham's chart in enag.

Quote from: burt on July 14, 2012, 09:49:09 AM

Immaterial

No it's not.  This entire thread we have been discussing due east and west courses.  Your response was explicitly to an example of following such a course.

I came from an oblique angle, so what? my argument still holds. A circle only has one great circle: its circumference. we can test whether there is only one great circle on earth by choosing an arbitrary direction and then choosing one that runs perpendicular to this, (whihc will inevitably intersect the other one) if a plan sets off on one and then the other, if on both runs it ends up back where it started: the earth is not flat, this talk about compassess muddies what is actually going on.