Earth’s alleged 25,000 mile circumference never verified and documented.

You like many others can claim Earth has roughly a 25,000 mile circumference but that does not make it true. It has to be verified and documented, but it never has been. The Greeks were good at popularizing myths and they’ve done a good Job with the Globe myth.

Myths are popular in this world and at this point, Globe Earth as proclaimed is all pseudoscience until someone can prove otherwise.

Don't say we're morons when none of you have the facts of a 25,000 mile circumference. We are stating facts on this issue and we are still waiting!

Good luck!

No unrelated issues or passing the buck, please.

https://en.wikipedia.org/wiki/Earth%27s_circumference

Measurement of Earth's circumference has been important to navigation since ancient times. It was first calculated by Eratosthenes, which he did by comparing altitudes of the mid-day sun at two places a known north–south distance apart. In the Middle Ages, al-Biruni developed a way to perform the calculation from a single location and made a measurement at Nandana in present-day Pakistan.

In modern times, Earth's circumference has been used to define fundamental units of measurement of length: the nautical mile in the seventeenth century and the metre in the eighteenth. Earth's polar circumference is very near to 21,600 nautical miles because the nautical mile was intended to express 1/60th of a degree of latitude (i.e. 60 × 360), which is 21,600 partitions of the polar circumference.

This does not have the information you seek?

So what is the circumference?

It has been verified as you can easily find multiple peer reviews of Eratosthenes. https://www.google.com/search?q=earth+circumference+peer+review&oq=earth+circumference+peer+review&aqs=chrome..69i57j33.8447j1j7&sourceid=chrome&ie=UTF-8.

It's a simple search actually.

It's not pseudoscience, it has been proven. I can turn this around and ask you: Is the (size of the) flat Earth verified and documented? If so, I'd like to see some peer reviews of flat earth experiments.

Ok, the first step in our journey would be the ground speed of subsolar point.
Do you know what it is, and do you know how it can be measured?

Maybe the north pole bends the light.

Maybe the north pole bends the light.

”Maybe” is maybe not quite enough, here.

But do tell more. Which way does it bend it?

https://en.wikipedia.org/wiki/Earth%27s_circumference

Measurement of Earth's circumference has been important to navigation since ancient times. It was first calculated by Eratosthenes, which he did by comparing altitudes of the mid-day sun at two places a known north–south distance apart. In the Middle Ages, al-Biruni developed a way to perform the calculation from a single location and made a measurement at Nandana in present-day Pakistan.

In modern times, Earth's circumference has been used to define fundamental units of measurement of length: the nautical mile in the seventeenth century and the metre in the eighteenth. Earth's polar circumference is very near to 21,600 nautical miles because the nautical mile was intended to express 1/60th of a degree of latitude (i.e. 60 × 360), which is 21,600 partitions of the polar circumference.

This does not have the information you seek?

Was you there when Eratosthenes or Biruni measure? Names can not magically help your case. Those are not evidence of anything.

Were you there when the conspiracy to hide the true shape of Earth was born?

World seems to work quite well with that ~25 000 mile figure. Flat Earth does not work with any of the numbers you attach to it. Kinda funny, no?

EDIT: First things first. You, Plat, Mike, and New Earth figure out a model you agree on first. Then start defending it together. Makes for a stronger front.

You like many others can claim Earth has roughly a 25,000 mile circumference but that does not make it true. It has to be verified and documented, but it never has been.

This depends on what you mean by "verified".
If you mean someone has to go out with a tape measure and measure it, then no, it hasn't been verified.
If you just mean shown to be that, then it has been countless times, including on a day to day basis with the use of GPS which relies upon that to be able to determine position.

Don't say we're morons

Don't worry, you're not a moron.
You are wilfully ignorant, blatantly lying about reality and hiding from the facts so you can pretend Earth is flat.

As for your images:
The experiment, when completely removed from context, is inconclusive. This is because it is unconstrained and as the height of the sun varies so to does the curvature.
But it wasn't an experiment with no context.
It was an experiment done after it was already shown that the sun is very far away and that Earth was round.
In this context, it did prove Earth had a circumference of roughly 40 000 km.

But don't worry, even if you want to ignore all that historical context, the only reason it is an unconstrained solution is because there were just 2 points.
We can do better by taking more points.

A good example to start with is Polaris.
Its altitude in the sky is known to vary with position.
As you move away from the north pole, it gets to a lower position. Importantly, this relationship is linear.
i.e. it is of the form, a=a0-kd.

This shows Earth is round.

A simple example is taking 3 points, the equator, the north pole, and half way between.
For the north pole and 45 degrees north, there are a multitude of solutions just like Eratosthenes. The simplest 2 are a round Earth with the 45 degrees spanning 5000 km and Polaris being very distant; and a flat Earth with Polaris 5000 km above the pole.

But when you travel an extra 5000 km to the equator and observe Polaris at/near the horizon, only one of this is consistent.
With a RE, travelling these extra 5000 km should put Polaris at an altitude of 0 degrees.
But with a FE and Polaris 5000 km above the north pole, Polaris should appear at an altitude of 26.6 degrees.

If instead we take the 2 points of the equator and the pole, we get the same solution for a RE, but for a FE we get Polaris at basically no height above the north pole.
If instead we take the 2 points of the equator and 45 degrees north, we get the same solution for a RE, but for FE we get Polaris at basically no height above a location just north of 45 degrees north.

So no, it is quite clear what the actual solution is.

And more lies in your image. The globe theory is not based upon Earth's circumference.
It is based upon the mountains of evidence which indicate Earth is round. The circumference is part of that.

As pointed out to you before, the curvature has been verified countless times. You wishing to remain wilfully ignorant of that will not change that fact.

Maybe the north pole bends the light.

Why does it bend, and more importantly, why in a particular direction?

Also, does this bending then have significant implications for claimed proof of a FE, such as the Bedford level experiment, where the bending of light should result in some of the object being hidden as well, just like the curvature of Earth should?

Was you there when Eratosthenes or Biruni measure? Names can not magically help your case. Those are not evidence of anything.

You can ignore history if you want, but don't worry, this isn't something limited to just history. You don't need to rely upon what they say. You can go and do the experiments yourself.

Maybe the north pole bends the light.

Cannot be an explanation since a flat earth does not have a north pole.

Yet another lie from Plat Terra.
Just shows his lack of research.

https://gisgeography.com/wgs84-world-geodetic-system/
https://en.wikipedia.org/wiki/World_Geodetic_System

You like many others can claim Earth has roughly a 25,000 mile circumference but that does not make it true. It has to be verified and documented, but it never has been. The Greeks were good at popularizing myths and they’ve done a good Job with the Globe myth.

Myths are popular in this world and at this point, Globe Earth as proclaimed is all pseudoscience until someone can prove otherwise.

Sorry to disappoint you but:

• Science does not pretend to "prove" things but only to provide the best theory that fits all of the evidence available.
  
  
• From around 300 BC the Earth was accepted as being curved and some evidence, such as the shape of the earth's shadow showed it as probably spherical.
  Since that time more and more evidence has accumulated and the spherical shape was accepted as fitting available evidence.
  
  
• Eratosthanes, in 205 BC, never set out to "prove the earth to be a Globe", that was taken as a given by his time.
  

Don't say we're morons when none of you have the facts of a 25,000 mile circumference. We are stating facts on this issue and we are still waiting!

Good luck!

No unrelated issues or passing the buck, please.

You state that "We are stating facts on this issue" but you have never proven the earth to be flat, so how can you claim that?

I'll only bother with your bit about the Eratosthanes measurement but of course, I'll "pass the buck because you have not thought the matter through.
He measured an angle difference of about 7.2° for the 800 km from Alexandria to Syene.

Now I realise that Eratosthenes only measured the angle to the sun at two locations and his measurements could be interpreted to mean either:

• that if the Earth were flat the height of the sun would be close to (800 km)/tan(7.2°) = 6333 km or 3936 miles - funny, that's not 3000 miles as claimed.
  
  
• but if the Earth were spherical it's circumference would be about (800 km) x (360°/7.2°) = 40,000 km or 24,860 miles - close to the accepted circumference.

But, just suppose that an Eratosthanes type measurement were repeated but with many more than the two points that he used as in:
The Eratosthenes Experiment: Proving the Earth is Spherical


Now you will find that on a flat earth the measured angles to the sun do not meet at a single point as in:

On the Globe, however, they are all very close to being parallel and pointing to a very distant sun.

Sly Sparkane did arrange for an experiment of this type to be repeated and he describes it here with "23 participants in 9 different countries":

These are the results of a group project which took place during the September Equinox 2017. 23 participants in 9 different countries conducted a simple scientific experiment similar to that of Eratosthenes over 2000 years ago.

The test is simple. Using the Latitude of each participant (as Longitude will be either 180° or 0°) The sun's elevation angle was measured during Solar Noon. These angles were then placed across both a Flat Plane and a Sphere to see which model the angles correspond to.

Do I have to tell you the results?

And this video shows the results:

Flat Earth: Debunked by Sly Sparkane

A number of others have done the Eratosthenes type experiment but at many more than two locations and the results always confirm theEarth to be a Globe.
Most people accept the TimeAndDate.com values for sun altitude at solar noon and they give the same result.

So, the extended Eratosthenes' measurement seems to provide quite solid evidence for this curvature that you keep demanding.

Where did you get the 25000 miles figure from if it’s never been documented?

Quote from: faded mike on November 02, 2019, 01:03:33 PM

Maybe the north pole bends the light.

Why does it bend, and more importantly, why in a particular direction?

Also, does this bending then have significant implications for claimed proof of a FE, such as the Bedford level experiment, where the bending of light should result in some of the object being hidden as well, just like the curvature of Earth should?

Quote from: wise on November 02, 2019, 01:37:25 PM

Was you there when Eratosthenes or Biruni measure? Names can not magically help your case. Those are not evidence of anything.

You can ignore history if you want, but don't worry, this isn't something limited to just history. You don't need to rely upon what they say. You can go and do the experiments yourself.

Because it's something you and i don't know all about.

Sorry for the off topic Plat Terra.

 I'm surprised no one seems to be coming forth defending "round" earth having actually witnessed these measurements being taken.

Quote from: JackBlack on November 02, 2019, 02:58:43 PM

Quote from: faded mike on November 02, 2019, 01:03:33 PM

Maybe the north pole bends the light.

Why does it bend, and more importantly, why in a particular direction?

Also, does this bending then have significant implications for claimed proof of a FE, such as the Bedford level experiment, where the bending of light should result in some of the object being hidden as well, just like the curvature of Earth should?

Quote from: wise on November 02, 2019, 01:37:25 PM

Was you there when Eratosthenes or Biruni measure? Names can not magically help your case. Those are not evidence of anything.

You can ignore history if you want, but don't worry, this isn't something limited to just history. You don't need to rely upon what they say. You can go and do the experiments yourself.

Because it's something you and i don't know all about.

Sorry for the off topic Plat Terra.

 I'm surprised no one seems to be coming forth defending "round" earth having actually witnessed these measurements being taken. You'd think coming onto the site and pushing roundism you'd be brandishing your eye witness info. Like whats going on here when you guys make a hobby of coming here to debate and don't even have pictures of these measurements being taken.

I'm confused. What would you like pictures of?

Quote from: faded mike on November 02, 2019, 10:41:03 PM

Quote from: JackBlack on November 02, 2019, 02:58:43 PM

Quote from: faded mike on November 02, 2019, 01:03:33 PM

Maybe the north pole bends the light.

Why does it bend, and more importantly, why in a particular direction?

Also, does this bending then have significant implications for claimed proof of a FE, such as the Bedford level experiment, where the bending of light should result in some of the object being hidden as well, just like the curvature of Earth should?

Quote from: wise on November 02, 2019, 01:37:25 PM

Was you there when Eratosthenes or Biruni measure? Names can not magically help your case. Those are not evidence of anything.

You can ignore history if you want, but don't worry, this isn't something limited to just history. You don't need to rely upon what they say. You can go and do the experiments yourself.

Because it's something you and i don't know all about.

Sorry for the off topic Plat Terra.

 I'm surprised no one seems to be coming forth defending "round" earth having actually witnessed these measurements being taken. You'd think coming onto the site and pushing roundism you'd be brandishing your eye witness info. Like whats going on here when you guys make a hobby of coming here to debate and don't even have pictures of these measurements being taken.

I'm confused. What would you like pictures of?

Have you witnessed the biruni or other experiment showing the curvature?

Quote from: Stash on November 02, 2019, 10:50:07 PM

Quote from: faded mike on November 02, 2019, 10:41:03 PM

Quote from: JackBlack on November 02, 2019, 02:58:43 PM

Quote from: faded mike on November 02, 2019, 01:03:33 PM

Maybe the north pole bends the light.

Why does it bend, and more importantly, why in a particular direction?

Also, does this bending then have significant implications for claimed proof of a FE, such as the Bedford level experiment, where the bending of light should result in some of the object being hidden as well, just like the curvature of Earth should?

Quote from: wise on November 02, 2019, 01:37:25 PM

Was you there when Eratosthenes or Biruni measure? Names can not magically help your case. Those are not evidence of anything.

You can ignore history if you want, but don't worry, this isn't something limited to just history. You don't need to rely upon what they say. You can go and do the experiments yourself.

Because it's something you and i don't know all about.

Sorry for the off topic Plat Terra.

 I'm surprised no one seems to be coming forth defending "round" earth having actually witnessed these measurements being taken. You'd think coming onto the site and pushing roundism you'd be brandishing your eye witness info. Like whats going on here when you guys make a hobby of coming here to debate and don't even have pictures of these measurements being taken.

I'm confused. What would you like pictures of?

Have you witnessed the biruni or other experiment showing the curvature?

You mean have I measured the dip and calculated the radius myself ala Biruni. No. Am I surveyor who performs leveling measurements with a theodolite and logging geodetic curvature data as part of the WGS84? No. 

The claim is that the circumference of the earth has never been verified and documented. Have I personally verified and documented it as described above? Not with pictures from me. But it's been verified for a couple a thousand years by countless others, by you, me, just about everyone. And is done so every minute of every day with every long haul flight and cargo passage that transports humans and goods all around the planet. Every time you look down at the GPS on your phone.

You've mentioned that you've flown in a plane before. How do you suspect pilots calculate their fuel needs, their route, their distance? All so they arrive when and where they are supposed to and so they don't drop out of the sky. How do you suppose tankers navigate across oceans? They use, GPS, charts, maps, all referencing a spherical coordinate system relative to the oblate spheroid we live on.

So yeah, the circumference has been verified and documented every minute of every day, over and over again by 10's of millions of people, ourselves included.

Because it's something you and i don't know all about.

I don't know what you mean by that.
Do you mean we don't have all the details of every experiment that has been run?

We know enough to know that it is consistent with a RE, not a FE.

I'm surprised no one seems to be coming forth defending "round" earth having actually witnessed these measurements being taken.

What would be the point?
Look at how wise rejects the historical accounts. Do you think he would accept REers claiming to have done the measurements?
There is no point in REers repeating the measurements to show Earth is round as FEers will happily reject it.

Also, if we trust the multitude of data on the internet we don't need to do it.
The question then becomes if we should trust it?
There is no sane reason to lie and pretend Earth is round.
There is even less to lie and pretend that a round Earth has a different radius/circumference.

We can look up where the sun appears in any given location, including our own, and compare it to what is observed.
People often do that for sunrise and sun set, 2 things which should never happen on a FE where the sun is always above the disk.

The height of the sun for a FE, with the sun always above the disk, would be the sun touching the disk, which would prevent the sun from ever appearing high in the sky, so that can be ruled out. Meaning the only option is a round Earth.

But we can also take the data for the angle to the sun and use that in place of an actual experiment, which I have done and others have done as well.
And do you know what the result was? Earth is round.
Even wise has done this, but also including a fudge factor to try and make it fit for a FE. But it still showed a RE to match the best (especially with him unable to justify his fudge factor).

We could do it, but what is the point?

If you tried to go over everything science has shown, trying to gather the evidence yourself, you would spend your entire life doing so, and still not be able to catch up.

As for Al Bruni, here is an example of that:
https://flatearth.ws/water-level-horizon



These all quite simply show that Earth is round.

Eratosthenes didn't "prove" the sphericity of the Earth.
It was already established.
He just measured the size.

The shape was already determined by many other observations before him.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I asked about subsolar point because it can be used
to measure circumferences of parallels between two tropics.

One of those parallals is "Parallel Zero" (the Equator).

More than once was shown here that the Equator has the biggest circumference
and that parallels both to the north and to the south are shorter.

For example:

Jilib: longitude – 42.78 degrees east
Kampala: longitude – 32.57 degrees east, distance from Jilib – 1136.5 km
Mbandaka: longitude – 18.29 degrees east, distance from Kampala – 1590 km
Libreville: longitude – 9.47 degrees east, distance from Mbandaka – 981.3 km

From Jilib to Libreville is 3708 km and 33.31 degrees of longitude.
It makes ground speed of subsolar point to be 3708 / 33.31 * 15 = 1669.768 km/h.
That speed multiplied by 24 h gives circumference of Equator to be 40074.45 km

Ofcourse there is error.
Every measurement has errors.
But how big is our error?
Checking Equator circumference at shorter distances inbetween gives
Between Jilib and Kampala we calculate 1669.686 km/h, which gives 40072.48 km.
Between Kampala and Mbandaka we get 1670.168 km/h, giving 40084.03 km.
Between Mbandaka and Libreville we get 1668.877 km/h, which gives 40053.06 km.

All values are very close to each other. Our error is below 0.05% (below 500 ppm – parts per million).

Ok, we have
Equator circumference of 40075 kilometers.
(Give or take kilometer or two.)

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Now, let’s go to Australia.
Tropic of Capricorn is at 23.44 degrees south.
I found two places at about 22 degrees south.
Difference is not big, we shall still have pretty low error.
Anyone can find places closer to 23.44 degrees south and test the method personally.

Sandover in Northern Territory: 135.93 degrees east.
Telfer in Western Australia: 122.15 degrees east.

Longitude difference – 13.78 degrees, distance – 1423.22 km.
Speed of subsolar point will be 1423.22 / 13.78 * 15 = 1549.22 km/h,
which gives circumference of that latitude as 37181 km.

Circumference of the Earth at 22 degrees south: 37181 km.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Two places in India, almost exactly at Tropic of Cancer, 23.4 degrees north.
From Durgapur to Bhuj is 17.61 degrees and 1805 km.
1805 / 17.61 * 15 = 1537.48 km/h, which gives 36899.52 km (36900).

Third number that we wanted to know is
circumference of Tropic of Cancer: 36900 km.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Now we know circumferences of the Earth at different latitudes as follows:
around 23.4 deg north – 36900 km (22 930 miles).
around  the  Equator – 40075 km (24 900 miles).
around 22 deg south – 37181 km (23 100 miles).

Try to scale and fit those on some flat surface.

Quote from: Stash on November 02, 2019, 10:50:07 PM

I'm confused. What would you like pictures of?

Have you witnessed the biruni or other experiment showing the curvature?

Have you measured the circumference of the Earth, the radius of the Earth or the diameter of the flat Earth?
If not why are you so negative about any claimed measurement.

Here is a video showing Mathias Kp "Calculating radius of globe Earth using horizon drop""

He shows the calculations from each altitude with these results:

His radii are in metres and the accepted average radius is 6371000 m so his results are not very accurate.
Mathias Kp uses the angle drop to the horizon that he had previously measured using a theodolite from elevations from 5 m to 184 m as shown in this video".



Al Biruni achieved a far better result but used a much higher elevation.
This site gives a good overview of Al Biruni and his work: Al-Biruni's Classic Experiment: How to Calculate the Radius of the Earth..
"Biruni's stated radius of 6336 km is also very close to the original value" but I feel his apparent accuracy might be a little fortuitous.

Many others have replicated the Eratosthenes type measurement. This is a very "light-hearted one " (and not very accurate one ):

Calculating The Circumference of The Earth by ScienceC

And here's another, again not pretending to be rigorous but demonstrating the principle that Eratosthenes used:

Eratosthenes - Measuring the Earth by BlueMarbleScience
He puts a correction below the video:

Correction: The length of the shadow shown on the triangle during the geometric demo was actually 17.5" - not 14.5". The actual half-size triangle was 8.75" along that side.

More Platt Error

Earth curvature measured and verified by every land survey carried out in the last 500 years.

Even a good old Theodolite, can measure vertical angle differences over relatively short distances.

This has been pointed out to you on a number of occassions

Is there a flat earther response to the Sly Sparkane youtube video () in this thread?

I am currently a round earth skeptic, new to considering the shape of our earth realm.

edit: I just realized how recent this post is to my reply. I am looking forward to flat earther responses.

What is the verified surface curvature over the center of South Louisiana, who documented it and does it conform to a sphere with a 25,000 mile circumference?

What is the verified surface curvature over the center of South Louisiana, who documented it and does it conform to a sphere with a 25,000 mile circumference?

I don't understand why you use that image in reference to Earth curvature. Curvature and elevation are two separate things.

Is this a trick question?

Quote from: Plat Terra on November 03, 2019, 11:54:29 AM

What is the verified surface curvature over the center of South Louisiana, who documented it and does it conform to a sphere with a 25,000 mile circumference?

I don't understand why you use that image in reference to Earth curvature. Curvature and elevation are two separate things.

Is this a trick question?

I don't understand. Please explain.

Quote from: SomeDutchGuy on November 03, 2019, 11:57:16 AM

Quote from: Plat Terra on November 03, 2019, 11:54:29 AM

What is the verified surface curvature over the center of South Louisiana, who documented it and does it conform to a sphere with a 25,000 mile circumference?

I don't understand why you use that image in reference to Earth curvature. Curvature and elevation are two separate things.

Is this a trick question?

I don't understand. Please explain.

To explain this easy: Curvature is the "roundness" of a surface. Elevation is the height (or depth) of the surface compared to the sea level.

Why you want to know the measurement of curvature specifically in Southern Louisiana I don't know. Why would it be different from measurements in Europe or Asia or Africa or wherever?

I don't understand. Please explain.

Summary of every one of your posts.

Quote from: Plat Terra on November 03, 2019, 12:00:38 PM

Quote from: SomeDutchGuy on November 03, 2019, 11:57:16 AM

Quote from: Plat Terra on November 03, 2019, 11:54:29 AM

What is the verified surface curvature over the center of South Louisiana, who documented it and does it conform to a sphere with a 25,000 mile circumference?

I don't understand why you use that image in reference to Earth curvature. Curvature and elevation are two separate things.

Is this a trick question?

I don't understand. Please explain.

To explain this easy: Curvature is the "roundness" of a surface. Elevation is the height (or depth) of the surface compared to the sea level.

Why you want to know the measurement of curvature specifically in Southern Louisiana I don't know. Why would it be different from measurements in Europe or Asia or Africa or wherever?

How is this?

What is the verified surface curvature over the center of any landmass, who documented it and does it conform to a sphere with a 25,000 mile circumference?