Idea to test curvature of Earth:

Originally posted by twhitehead
That's certainly a good idea, but I believe identifying the direction of non-line of sight radio waves is extremely difficult as they tend to reflect rather easily.

Here in Southern Africa, the most popular satellite TV comes from a couple of satellites. One could measure the angle of satellite dishes. I do know for a fact that dishes in Cape Town poin ...[text shortened]... e in Zambia, but that would be the case even on a flat earth as the satellites are to the north.

The advantage of gigahertz frequencies is they are more line of sight whereas say 50 mhz and below are more susceptible to atmospheric disturbances, Ionospheric defraction and so forth. At 5 ghz, those waves could care less about the ionosphere, but there are still semi-ionized blobs in the lower atmosphere that can reduce the intensity of the beams, I used to work on Space diversity microwave communications links and one of my jobs was to monitor the SNR of the signals, two dishes about 20 meters apart and the same on the other end, the SNR was up and down like a yo you but at different times even though the two dishes were only 20 meters apart. One SNR would be in the toilet but the other 60 db stronger but a few milliseconds later the opposite happened.

So a signal combiner allowed almost perfect communications for short links up to a couple hundred Km apart. Of course all that technology has been replaced by satellites now but it worked well for the time. There was an alternate means developed at the time, called frequency diversity instead of space diversity, where the radio had 17 channels of different frequencies and only one microwave dish, in fact, not even on a tower but on the ground, a lot more portable where the dish was made like slices of an orange skin and put together in the field and at the other end the same. They would talk to each other in millisecond segments of time, 'chan 1 is good, lets go to chan 1.

A few milliseconds later, the radio notices chan 1 is in the toilet, they scan continuously and they find, chan 14 is clear switch there, and so forth, all fast enough that 24 separate audio channels could be transmitted with no loss of data. But the kind of data you would be after would be done just integrating a large sample of signals to suss out the actual angles involved.

Getting back to the gyroscope technique, I wonder how long a rotor could keep up to speed if it was in a vacuum and supported by magnetic bearings instead of physical bearings? If it could maintain say 90% of it's spin velocity for 6 hours it would show a 90 degree shift and such with no need for extra motors and the power requirements for the same. I know they are researching vacuum magnetic bearings for power storage, get the rotor up to 100,000 RPM and it stores quite a bit of energy and of course a gyroscope wouldn't need that extreme RPM's to do the curveature experiment. What do you think?

At no point above do you tell us whether it is possible to accurately determine the direction of a radio source that is over the horizon.

Originally posted by sonhouse
Getting back to the gyroscope technique, I wonder how long a rotor could keep up to speed if it was in a vacuum and supported by magnetic bearings instead of physical bearings? If it could maintain say 90% of it's spin velocity for 6 hours it would show a 90 degree shift and such with no need for extra motors and the power requirements for the same. I know ...[text shortened]... a gyroscope wouldn't need that extreme RPM's to do the curveature experiment. What do you think?

I think good luck finding a flat earthier with access to vacuums and magnetic bearings.
And how do you start it rotating in the first place?

Originally posted by twhitehead
It has everything to do with gravity. The surface of water is a reflection of the direction of gravity. Water levels have been used since ancient times for this very reason.
As I say, all you need is two water levels (or something more accurate perhaps) at a distance and a line of sight between them. Measure the difference in the levels and you are done. ...[text shortened]... tance apart and point them towards each other. If both point above each other then you are done.

Similarly, two lasers attached to plumb bobs would point straight up. Place them in a valley far enough apart, then climb a mountain at night and see whether the beams are parallel--if so, the Earth is flat, if they diverge, the Earth is curved.

EDIT: that the Earth is curved follows from the fact that sunlight shines vertically down a well, or casts a shadow, depending on where the well is on the Earth's circumference. A fact known in ancient times.

https://www.britannica.com/biography/Eratosthenes

http://www.windows2universe.org/citizen_science/myw/w2u_eratosthenes_calc_earth_size.html

Originally posted by moonbus
Similarly, two lasers attached to plumb bobs would point straight up. Place them in a valley far enough apart, then climb a mountain at night and see whether the beams are parallel--if so, the Earth is flat, if they diverge, the Earth is curved.

EDIT: that the Earth is curved follows from the fact that sunlight shines vertically down a well, or casts a sh ...[text shortened]... nes

http://www.windows2universe.org/citizen_science/myw/w2u_eratosthenes_calc_earth_size.html

Wouldn't you get the same effect if the earth was flat and the sun much closer?

Originally posted by twhitehead
Wouldn't you get the same effect if the earth was flat and the sun much closer?

That depends...is it a flat sun?

Originally posted by moonbus
Similarly, two lasers attached to plumb bobs would point straight up. Place them in a valley far enough apart, then climb a mountain at night and see whether the beams are parallel--if so, the Earth is flat, if they diverge, the Earth is curved.

EDIT: that the Earth is curved follows from the fact that sunlight shines vertically down a well, or casts a sh ...[text shortened]... nes

http://www.windows2universe.org/citizen_science/myw/w2u_eratosthenes_calc_earth_size.html

Eratoshenes' achievement was impressive, but he did not prove that the world is a sphere. Rather he calculated the circumference of the world, with remarkable precision given the equipment he had, assuming that the world is a sphere. So what he showed is that if the world is a sphere then it's circumference is 250,000 stadia. The objective of this thread, in so far as it has one, is to show that the Earth is a sphere using local information, in the face of extreme skepticism. It's not clear to me that that is possible since even if one shows that locally the geometry is that of a sphere it does not follow that globally the Earth is a sphere (nearly). I'm assuming that this thread is an attempt to show that FreakyKBH's conspiracy theory is wrong. The problem is that a simple circumnavigation won't work, he'll just claim that one has travelled in a circle on a plane. One would have to set out a number of travellers all going in "straight" lines from a point and so demonstrate that their paths all cross once at the antipode before returning to their original point. This is not reproducible on a plane.

Originally posted by DeepThought
One would have to set out a number of travellers all going in "straight" lines from a point and so demonstrate that their paths all cross once at the antipode before returning to their original point. This is not reproducible on a plane.

And in practicality not reproducible in reality even with a plane. We simply don't have too many planes that will fly around the world non-stop, and who is going to check that they are flying in a straight line given that almost all navigation systems are treated as fake by flat earthers?

I believe one of the best pieces of evidence that we are all directly tied to is the time of the sun. It is rather difficult to explain time of day differences without a spherical spinning earth. I have personally travelled across timezones, and often made calls to people in very different timezones and even more frequently communicated with people in different timezones. And we see it live on TV every new year with the progress of fireworks celebrations across the globe.

Originally posted by DeepThought
Eratoshenes' achievement was impressive, but he did not prove that the world is a sphere. Rather he calculated the circumference of the world, with remarkable precision given the equipment he had, assuming that the world is a sphere. So what he showed is that if the world is a sphere then it's circumference is 250,000 stadia. The objecti ...[text shortened]... at the antipode before returning to their original point. This is not reproducible on a plane.

Ah, you mean a flat-earther might claim that the Earth is curved only locally but still not a sphere, in other words, that the Earth is a bowed pancake and that Eratosthenes' calculation applies only to the arc not to a sphere. In the face of such extreme skepticism, I agree -- one would need additional means to globalize the evidence.

I do however, have an objection to the idea that a wall of ice in Antartica is what keeps the oceans from flowing out into space: such a wall would not keep the atmosphere from flowing out into space. I do not see how flat-earthers can explain what keeps the atmosphere here.

Furthermore, if the the circumference of a flat Earth is assumed to be Antartica, then the distances between the southern tips of Africa and So. America and NZ must be much greater than commonly supposed, and ships/planes making the journey from tip to tip would have to take much longer than in fact they do.

EDIT: Oh yes, and the rate of fuel consumption would have to radically change for those crossings, compared to flying any more northerly route, with no physical or engineering explanation for such change.

Originally posted by twhitehead
Wouldn't you get the same effect if the earth was flat and the sun much closer?

I suspect that a great many well-established astronomical facts would have to be 're-calibrated' in order to be made consistent with the supposition of a much nearer sun. Such as the amount of energy the sun radiates and its surface temperature and its mass. Otherwise, it would have sucked our world in after having fried it long ago.

I suppose that a really dedicated skeptic might claim that NASA and ESA and every astronomical observatory and university in the world are part of a conspiracy to keep a great big flat secret. But given that Hilary Clinton's campaign couldn't even keep a few emails secret, it is hardly credible that a conspiracy encompassing NASA, ESA, and every astronomical observatory and university in the world could keep a secret without some Snowden-chap blowing the cover off.

Originally posted by moonbus
Ah, you mean a flat-earther might claim that the Earth is curved only locally but still not a sphere, in other words, that the Earth is a bowed pancake and that Eratosthenes' calculation applies only to the arc not to a sphere. In the face of such extreme skepticism, I agree -- one would need additional means to globalize the evidence.

I do however, have ...[text shortened]... to flying any more northerly route, with no physical or engineering explanation for such change.

They seem not to mind denying the validity of most of physics. I was going to write post-Aristotelian physics, but, of course he had a spherical earth. Flat Earth societies made no sense from the time they were founded (circa 1850), but did allow their founders to sell pamphlets on the subject and give lectures, in other words the purpose was charlatanry.

Originally posted by moonbus

Furthermore, if the the circumference of a flat Earth is assumed to be Antartica, then the distances between the southern tips of Africa and So. America and NZ must be much greater than commonly supposed, and ships/planes making the journey from tip to tip would have to take much longer than in fact they do.

.

It's a huge global conspiracy by all governments and scientists alike to cover up the fact the Earth is actually flat. They have to exert huge effort to either rubbish or explain away whenever a layperson notices something fishy, which is inevitably often. What I don't get is what is the motive for this huge global conspiracy which has to be a powerful good motive given the huge difficulty and crippling economical cost and monumental effect to constantly maintain this Earth-is-not-flat conspiracy with ever more lies to cover up other lies to cover up other lies. Theories?

Originally posted by humy
It's a huge global conspiracy by all governments and scientists alike to cover up the fact the Earth is actually flat. They have to exert huge effort to either rubbish or explain away whenever a layperson notices something fishy, which is inevitably often. What I don't get is what is the motive for this huge global conspiracy which has to be a powerful good mot ...[text shortened]... not-flat conspiracy with ever more lies to cover up other lies to cover up other lies. Theories?

Follow the money!

Originally posted by moonbus
Furthermore, if the the circumference of a flat Earth is assumed to be Antartica, then the distances between the southern tips of Africa and So. America and NZ must be much greater than commonly supposed, and ships/planes making the journey from tip to tip would have to take much longer than in fact they do.

Flat earthers claim that this explains why many flights to not go direct but go north first. They also claim that anyone who has been on a direct flight is lying. (I have family members who have flown direct from SA to Australia.)

Originally posted by twhitehead
I have family members who have flown direct from SA to Australia.

And those planes did not run out of fuel on the way, did they? SA & Australia would have to be thousands of miles farther apart if the Antarctic were really the circumference of a flat disc.

Let them have their harmless delusion. Goodness knows, there are more dangerous wackos out there than flat-Earthers.