1. Rory

    Rory Senior Member

    There are quite a few threads on here discussing that. Here are six of the best ways to easily demonstrate that the horizon is below eye level:

    1. Use a professional theodolite. Eye level is where the crosshair is:


    2. Download and properly calibrate a theodolite app. Eye level is where the crosshair is:


    3. Make your own theodolite using a spirit level:


    4. Use parallel lines to find the vanishing point (which is always at eye level):


    5. Take a picture of eyes, with the camera at eye height, and see where the horizon is:


    6. Use a water level - after all, all flat earthers know "water always lies flat". ;)


    Number 5, by the way, is an example rather than a demonstration - the camera in that photo is probably slightly below eye level, therefore his eyes appear even more above the horizon than they normally would..
    Last edited: Oct 30, 2017
  2. yoda900

    yoda900 New Member

    Lots of great responses to the question I had, thank you! and rory, funny thing, shortly after I proposed my method of eye level, I actually wound up finding the video you posted as number 6. I am going to also read through the threads mick posted as it appears there is a lot of great information there. I was just thinking that adding the wrinkle of super zooming in, from a high enough point, on a clear enough day, it would be fun to see their resopnses. afterall, I think I should add in now to my scientific proposed experiment, it has to be a theodolite, it sounds like it is indeed a more accurate way to measure showing 0 degrees angle from the horizon, as it seems to literally show the exact angle to within 1/100 of a degree. Funny that flat earthers love to talk about theodolites being used to prove flat earth. I think the issue is that the are not utilizing it correctly or doing incorrect procedures . I don't think one of these could possibly prove anything BUT a round Earth.

    I do enjoy discussing with flat earthers the inconsistencies. I always like to aruge using math, physics and actual science. Because Math and scientific method, as everything demonstrated here is repeatable and verifiable. thank you!
  3. Chris Mist

    Chris Mist New Member

    I have used the search function and thought this might be the best place to ask a question or two.

    For the first time im stuck when debating a flat earther...
    I may go into more detail about my debate if needed, but the simple question is, does watching a ship appear to sink behind the horizon prove curvature? Or can the bottom of a boat disappearing the further away it gets be explained equally just by how light can bend?
  4. Trailblazer

    Trailblazer Moderator Staff Member

    It certainly demonstrates curvature. My response would be to get the flat Earth believer to draw a diagram of how he or she imagines the light rays to be bending, and why.
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  5. Chris Mist

    Chris Mist New Member

    Well... he says its due to perspective [...]

    Normally i could argue his simple "perspective" response, but im not totally sure about one thing. Which is, can a mirage make an object totally disappear?
    Could a ship, sailing further and further away, be obscured completely due to the mirage, and not curvature?
    Last edited by a moderator: Jan 23, 2018
  6. Mick West

    Mick West Administrator Staff Member

    It theoretically can, but there's two rebuttals:

    For a mirage to significantly hide or bring something into view, it's going to distort it. So the best examples are when there's a clear horizon, and an undistorted ship behind it.
    Metabunk 2018-01-23 09-37-21.

    It can't hide a mountain. So use that instead.
  7. Z.W. Wolf

    Z.W. Wolf Senior Member

    A ship disappearing below the horizon is not at all important to the theory, anyway. That the earth is a sphere explains why the ship disappears. But to my knowledge this was never cited by Aristotle or any philosopher before him as evidence for the spherical shape of the earth. Nor has it ever been an important part of the theory since then. There is much stronger evidence.

    There's a lot of misinformation out there about what led the Greek astronomers and philosophers to the sphere earth theory.

    Here's a good example, with my comments in brackets:


    This is what Aristotle actually wrote:


    Some people, it seems, are having a hard time visualizing why stars appear and disappear on a sphere Earth as you move north and south (not east and west). I haven't seen a good visual demonstration of this anywhere. The best thing I can recommend is getting a really big ball, the kind they have in a gym. Put your eye up to it really close at the top and then and move your head - without moving the ball - down across the surface. Notice what parts of the room are visible and not visible.

    Here's a crummy little GIF I made:

    The red line is your line of sight at your local southern horizon: things "below" the red line are hidden by the rim of the earth. Below the southern horizon, in other words. This is why new southern stars become visible as you move farther south on the sphere earth. Just reverse this and you'll see why Polaris disappears. The rim of the Earth is hiding it.

    The fact that the Greek astronomers of Aristotle's time had observed this phenomenon was the cruncher for them. From this time on the Greeks took it as fact that the earth is spherical.

    This explains why Europeans, when they sailed for the first time into the deep southern hemisphere saw things in the southern sky at night that no European (that we know of) had ever seen before. Things such as the Magellanic Clouds.


    Ships are relatively small objects seen at relatively short distances. And the atmosphere can play tricks. At times you can see the ship quite clearly, at other times it is highly distorted. This muddies the waters.

    You can sort of put a spin on the ship disappearing below the horizon phenomenon by citing largely fictitious quirks of refraction or fuzzy ideas about perspective, just because of the small scale involved. But how can you explain away the macro-phenomenon of new stars continually coming over the southern horizon as you travel hundreds or thousands of miles south?

    The real proof to the Greeks was the behavior of the stars and it should be immediately apparent in our time. This phenomenon is tremendously well established through the experience of millions of people over history. It is also easily noted if you personally travel a significant distance to the north or south, (and you are capable of keeping track of individual stars.)

    As has been pointed out, if you don't want to put in the effort of traveling hundreds of miles and observing stars. Rather than looking at ships, it's much better to look at relatively large things - e.g. islands - and change your altitude by hundreds of feet not just a few. You'll see big differences. Ships small, islands big.

    But it remains that the stars are best.

    I have to add one more thing. Another bit of misinformation: Aristotle himself made these observations of the stars and he originated the idea that this was proof of the sphere earth. False.

    There were many astronomers in his time but almost all records have been lost. Aristotle's writings do exist and preserve the earliest extant argument. But this was a team effort and Aristotle was citing a general consensus of the time.
    Last edited: Jan 23, 2018
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  8. DavidB66

    DavidB66 Member

    Moving on a bit from the Greeks, the philosophers of the Middle Ages also (for the most part) believed that the earth is a sphere. The reasons they gave are concisely set out in the most popular astronomical text of the period, the Tractatus de Sphaera of John of Holywood [Sacrobosco], written not long after the year 1200:

    THE EARTH A SPHERE. -- That the earth, too, is round is shown thus. The signs and stars do not rise and set the same for all men everywhere but rise and set sooner for those in the east than for those in the west; and of this there is no other cause than the bulge of the earth. Moreover, celestial phenomena evidence that they rise sooner for Orientals than for westerners. For one and the same eclipse of the moon which appears to us in the first hour of the night appears to Orientals about the third hour of the night, which proves that they had night and sunset before we did, of which setting the bulge of the earth is the cause.​

    FURTHER PROOFS OF THIS. -- That the earth also has a bulge from north to south and vice versa is shown thus: To those living toward the north, certain stars are always visible, namely, those near the North Pole, while others which are near the South Pole are always concealed from them. If, then, anyone should proceed from the north southward, he might go so far that the stars which formerly were always visible to him now would tend toward their setting. And the farther south he went, the more they would be moved toward their setting. Again, that same man now could see stars which formerly had always been hidden from him. And the reverse would happen to anyone going from the south northward. The cause of this is simply the bulge of the earth. Again, if the earth were flat from east to west, the stars would rise as soon for westerners as for Orientals. which is false. Also, if the earth were flat from north to south and vice versa, the stars which were always visible to anyone would continue to be so wherever he went, which is false. But it seems flat to human sight because it is so extensive.​

    SURFACE OF THE SEA SPHERICAL. -- That the water has a bulge and is approximately round is shown thus: Let a signal be set up on the seacoast and a ship leave port and sail away so far that the eye of a person standing at the foot of the mast can no longer discern the signal. Yet if the ship is stopped, the eye of the same person, if he has climbed to the top of the mast, will see the signal clearly. Yet the eye of a person at the bottom of the mast ought to see the signal better than he who is at the top, as is shown by drawing straight lines from both to the signal. And there is no other explanation of this thing than the bulge of the water. For all other impediments are excluded, such as clouds and rising vapors.​

    Also, since water is a homogeneous body, the whole will act the same as its parts. But parts of water, as happens in the case of little drops and dew on herbs, naturally seek a round shape. Therefore, the whole, of which they are parts, will do so. [English translation by Lynn Thorndike.]
    The Tractatus de Sphaera was a standard introductory text used in universities throughout Europe until the 16th century. A full text is here http://www.esotericarchives.com/solomon/sphere.htm . It can be used as an antidote to anyone who claims that the spherical earth was an invention of Columbus or Copernicus. (I haven't checked the online version against a printed source, but I do know that the quoted translator, Lynn Thorndike, was a very distinguished historian of science.)
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  9. Rory

    Rory Senior Member

    It's difficult to imagine you'll have much success getting through to someone with such an odd understanding of perspective.
    Are they suggesting this also? And are they therefore suggesting that the same mirage is present everywhere whenever a ship is seen to disappear bottom first?
  10. Chris Mist

    Chris Mist New Member

    I appreciate all the replies. The 'debate' i was having ended.
    Basically i stuck to the simple fact that a ship will always disappear from the bottom up and curvature best explains this.
    The photos that Mick posted got me thinking about how there isnt always atmospheric distortion, and therefore a mirage is obviously not the best explanation.
  11. Z.W. Wolf

    Z.W. Wolf Senior Member

    If you ever have a similar conversation, I think it should start with this: https://www.metabunk.org/all-the-ships-at-sea-a-pragmatic-test-of-earths-shape.t8954/

    IMO all FE conversations should begin with this. The conversation is dominated by discussions about theory. But theory has to be tested. Which model and which map has passed the test?

    FE belief is predicated on the odd idea that the map of the world is unknown and down right mysterious. But people have been traveling between the continents for hundreds of years. It's now a mundane activity.
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  12. Rory

    Rory Senior Member

    Some lovely diagrams from that text: very contemporary for something nearly 800 years old. :)


    Even got the tilt right (unlike some of the Wallace diagrams).
  13. Bunkmeister

    Bunkmeister New Member

    It is all about line of sight. Why does going up higher let you see more? Because it removes obstructions to line of sight. If you rise up 10 feet in your back yard, you will see above your neighbor's fence, higher yet and you see over a treeline further out, keep going and eventually you will be seeing over the curve of the earth. Zooming in can't remove an obstruction.
  14. Rory

    Rory Senior Member

    This is one of the best "zooming in to show a ship beyond the horizon" videos I've seen:

    Source: https://www.youtube.com/watch?v=HHXuJQ3_8J4

    Or, in gif form:


    The closest ship is the Princess Paula, stated at 8.86 miles, and the furthest one is the Glorious Mahuta, at 12.6 miles.

    With a camera height of 30 feet, the predicted hidden amounts at those distances are 1.5 feet and 17 feet.

    One thing I'll say, though: it sure looks like more than 17 feet of the Mahuta is missing.

    I've contacted the videographer to ask about that.
    Last edited: Apr 5, 2019
  15. Loki Thorson

    Loki Thorson New Member

    I see in that video that the Princess Paula is going across the horizon, would have been a good opportunity to test it by going to the beach or get lower. Must also point out that both the p900 and p1000 have short focal lengths of about 4mm at widest angle, this will give the effect of the scene being viewed much further back than with eyes only and so gives the impression of bringing back a ship into good view. In real life, the camera user will see the scene more clearer than the short focal length.
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