Re: Pre-satellite measurements of position
« Reply #40 on: December 12, 2018, 11:53:22 AM »
I'm quite interested in this idea of comparing distance measurements from Cook's voyages with modern values because if modern methods are reliable and difficult to refute across the globe then calculating the length of a degree of longitude north of the equator, on the equator and south of the equator should be simple. And if it then turns out that a degree of longitude is shorter anywhere south of the equator than on the equator, then there are consequences, because as Rowbotham (Earth not a globe) says:

"The following is the true state of the question:--If the earth is a globe, it is certain that the degrees of longitude are less on both sides of the equator than upon it. If the degrees of longitude are less beyond, or to the south of the equator, than upon it, then it is equally certain that the earth is globular" (my emphasis)

Offline edby

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Re: Pre-satellite measurements of position
« Reply #41 on: December 12, 2018, 03:26:50 PM »
I'm quite interested in this idea of comparing distance measurements from Cook's voyages with modern values because if modern methods are reliable and difficult to refute across the globe then calculating the length of a degree of longitude north of the equator, on the equator and south of the equator should be simple. And if it then turns out that a degree of longitude is shorter anywhere south of the equator than on the equator, then there are consequences, because as Rowbotham (Earth not a globe) says:

"The following is the true state of the question:--If the earth is a globe, it is certain that the degrees of longitude are less on both sides of the equator than upon it. If the degrees of longitude are less beyond, or to the south of the equator, than upon it, then it is equally certain that the earth is globular" (my emphasis)

I am going to follow this up shortly, but meanwhile here is a brief guide to the moons of Jupiter method. I always thought that it was a way of directly finding your position by parallax with the moons, but actually it’s an indirect way of finding it by telling the time. The moons transit Jupiter regularly so when the moon disappears behind the planet, we know what time it is where we are, hence what time it is at Greenwich.

This method is independent of whether earth is flat or a globe. If flat, then the sun has a circular orbit around the disc of the earth. If you know the exact time when it is directly ahead, you automatically know your longitude.

So, as Robin says (thanks), the key question is the length of a degree of longitude south of the equator. Equally key is that Rowbotham would agree. We have a simple Zetetic experiment to determine the shape of the earth.

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Offline RonJ

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Re: Pre-satellite measurements of position
« Reply #42 on: December 12, 2018, 03:27:43 PM »
It's pretty much a done deal.  Nautical charts and any other workable charts are still based upon the longitude lines converging at the South Pole. 

While I was at the mall yesterday I checked with one of Santa's elves.  That elf assured me that he was updating the training on Rudolf the Red Nosed Reindeer and making sure that the WGS-84 charts will be used for navigation this Christmas.  Now you have Popeye and Santa Clause depending upon world charts that have the longitude lines starting off at the equator with 1 nautical mile per minute in the distance between longitude lines down to zero distance at the South Pole.  That means that the longitude lines are converging.  By definition that's a globe earth South of the Equator.

Anyone can prove that the earth is a globe North of the equator by doing a simple experiment with simple equipment using the North Star.  That would prove that the earth is a sphere North of the equator.  Probably the same could be done in the Southern hemisphere using the Southern Cross. 

The basic question is simple really.  All the charts out there used by ship's crews and aircraft crews are based upon a globe earth.  Those crews use those charts for navigation.  Those same crews don't get lost or even complain that their charts are inaccurate.  The difference between a flat earth chart and a globe earth chart would have to be radical and wouldn't accurately represent that actual surface of the earth.  Therefore since the charts used are accurate and work and the charts used are based upon a globe earth it is simple logic to assume that the actual earth is also a globe South of the Equator. 
You can lead flat earthers to the curve but you can't make them think!