# An Easy Experiment to Debunk the Flat Earth by Observing the Size of the Sun

Discussion in 'Flat Earth' started by Mick West, Jan 31, 2016.

1. ### Mick WestAdministratorStaff Member

Agreed, although it's a bit disheartening that there's already a lot of photos on YouTube showing the sun getting "bigger' as it gets "closer". It's just flare though.

Really you'd just need two photos, say at 8AM and 12PM (noon) (then maybe at 4 also).

Again though the thinking that allows people to think "perspective" makes the sun go behind the horizon might also make it hard to them to accept this as evidence.

Here's an interactive simulation of what the sun would look like. Posted by David Ridlen on Facebook
http://tube.geogebra.org/student/2141849

I made a couple of GIFs for viewpoints in the Southern and Northern hemispheres, simplifying the text for easier communication. There are two thing to point out to the Flat Earth proponent:

1) The sun grows and shrinks in the Flat Earth model, but not in observed reality.

2) The sun never goes below the horizon in the Flat Earth model, but it does in observed reality.

Last edited: Aug 8, 2016
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2. ### Mick WestAdministratorStaff Member

I did a brief version of this experiment with a 50mm lens and some welders glass.

Unfortunately the images were not particularly good, and only taken two hours apart. But the goal here is more to develop a simple test that people can do at home.

While this does look a bit like trying to disprove a broad theory, it does actually debunk a specifci claim of evidence - that the sun gets bigger as it gets higher in the sky, proving it is is moving towards you. There are several videos along these lines:

Are they just trolling? Hard to say, but even if they are, they are attempting to provide an answer for the question "why does the sun sink below the horizon". They attempt to explain this with perspective (where the vanishing point is fixed a few thousand miles from the viewer), and use the "growing" sun as evidence of that. Photos without glare prove the sun is not changing apparent size, so perspective has nothing to do with it.

Again, this may seem too ludicrous to even address, but I think it's that ludicrousness that will eventually get people to see the light. Providing instructions for a simple test might give them the clarity to see the problem with "perspective" as a solution.

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3. ### Henk001Active Member

"Are they just trolling?" At least some seem to be sincere. I had a few "discussions" with them. Most seem to be inspired by religion combined with conspiracies as a "general explanatory model" (they have to assume that almost every scientist must have been deliberately lying for some millennia). On the one hand it is kind of fun sharpening your mind by thinking about why we take some things for granted and in the course of that finding out how solid the scientific evidence can be. On the other hand it can be frustrating, because most of them, when confronted with rebuttals don't seem to have the most basic knowledge about physics, mathematics and spatial awareness (space perception?) -- or they react like putting fingers in their ears and squeeze their eyes shut and singing loudly "lalalalalala, I can't hear you".

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5. ### ChewSenior Member

Dave Greg, an amateur astronomer in New Zealand, did it.

https://www.facebook.com/dave.greg1...32259086821.1073741921.100002201677137&type=3

Here is a compilation of his three photographs:

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6. ### Ross MarsdenSenior Member

Doesn't the Sun move from east to west, regardless of the shape of the Earth?

7. ### Mick WestAdministratorStaff Member

Yeah I think they were overly focussed on the size of the sun there, and missed that.

8. ### IntiActive Member

I like this: I've tried to make the same point here : http://roundearthsense.blogspot.co.uk/2016/03/55-if-sun-circles-over-and-around-earth.html

However, I've just posted a new thread about this video clip, which claims to show just what you describe: a sun shrinking as it sets.

https://www.metabunk.org/sun-apparently-shrinking-as-it-sets.t7408/

Last edited by a moderator: Mar 17, 2016
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9. ### ChewSenior Member

Good stuff. A few extra points for some of the stuff you briefly mentioned:

I've seen two flat earther claims about how the diameter of the Sun was measured with a sextant.

1. The altitude of the Sun was measured by flat earthers triangulating the altitude angle above the horizon from two different locations and then the angular diameter of the Sun was measured with a sextant and simple trigonometry was used to calculate the actual diameter. Of course this failed because they assumed the Earth was flat.

2. The angular diameter of the Sun was measured with a sextant and "since one minute of arc is equal to one mile" the Sun is 32 miles in diameter. Seriously. That's what some flat earthers claim. That's like if I were to measure your height with a sextant and it reads 45° then I concluded you are 2700 miles tall. They confuse the fact that one minute of arc of latitude on a map is equal to one (nautical) mile and since sextants can read in minutes of arc, then hey!, they must be the same. They also ignore the fact that according to their own model the Sun should appear smaller the closer it is to the horizon. And that they can measure the angular diameter of the Sun themselves using a sextant and see for themselves the Sun doesn't change size through the course of the day (barring refraction effects at very low altitude angles).

You said the lowest the Sun could appear is to perhaps touching the horizon. The most quoted diameter of the flat earth I've seen is 25,000 miles. If you were at the "south pole" of the flat earth (i.e. standing at the edge) then the lowest the Sun could ever appear is when it is on the opposite side of the disc during the December solstice. The Sun would be the distance from the edge to the north pole (180°) to the equator on the other side from you (another 90°) then down to 23.5° South to the Tropic of Capricorn. That is 293.5° of latitude, or 20,266 miles. At an altitude of 3000 miles then the Sun should still be 8.4° above the horizon. Even that is too far above the horizon for them to invoke their magical "vanishing point".

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10. ### ChewSenior Member

Any celestial body you can see can be used for celestial navigation if you know their coordinates. I once shot Comet Hale-Bopp with a sextant using coordinates printed in Sky & Telescope magazine. The Sun is often used for determining your latitude at Local Apparent Noon. The coordinates for the Sun published in the Nautical Almanac and all other almanacs are for the center of the Sun. You can't accurately eyeball the center of the Sun so you will line up the upper or lower limb of the Sun with the horizon in your sextant and apply a correction for the apparent angular size of the Sun. This correction, called the "Semi-diameter", abbreviated "SD", is printed at the bottom of the Sun column on the Daily Pages. Three days of data are covered by one page. A perusal of the semi-diameter of the Sun through the Daily Pages shows it changes very slowly from day to day. If the flat earth model were true then you would need a table of corrections to correct for the changing size of the Sun (and for the Moon) as it changes altitude angle above the horizon. But there is no such table in any almanac.

https://books.google.com/books?id=C...UKRSYKHamLCywQ6AEIPjAE#v=onepage&q=SD&f=false

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11. ### Henk001Active Member

There is still another problem with the sun hovering above a flat earth disk.

Given the observational fact that every degree of latitude is the same distance (111km or 69 miles; but that is irrelevant) the Flat Earth Model (FEM) is mathematically impossible. As I will show.

For the sake of simplicity, let us assume it is march 21 at noon. The sun is right above the equator. Now lets consider an observer α degrees north along the local meridian. Then we see the sun under that same angle α and the distance to the equator is 111km x α. [Math alert] In the FEM the distance and the sun’s hovering height h form the rectangle sides of a rectangular triangle and h is the adjacent side to α. Thus h (km)= 111α/tan α. [end alert]

Conclusion: for every latitude the computed hovering height will be different. Which is impossible. Flat Earth is flat out wrong.
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And now I'm at it, another impossibility lies in the fact that for observers below the equator (for FE's: "outside" the equator) looking south at the night sky (for FE's: looking outward towards the big ice wall of Antarctica), two observers on opposite sides of the disk (say, Sydney and Buenos Aires) see the same south celestial pole at the same time.
You cant see the same point looking in opposite directions.

Last edited: Mar 22, 2016
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12. ### Mick WestAdministratorStaff Member

Eventually the hard core flat earth believers are forced to invoke some kind of bending light. i.e. the Earth is flat, but light bends in such a way that it appears round.

At that point it's probably best to just leave them alone.

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13. ### GuiNew Member

Good Afternoon,

A flatearther here (the page is brazillian, so it's in Portuguese) made the following claim about the sunset in a Flat Earth:

The translation is followed below:

Does this makes sense or that is any error in the explanation?

14. ### Henk001Active Member

It doesn't make any sense. The decrease in size has nothing to do with a plane you are in, or to put it otherwise: the observer and the sun are always together in some mathematical plane.

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15. ### RorySenior Member

It seems most flat earthers say the sun is around 3000 miles high - I've seen other answers - but when I ask them how high exactly and how this figure was arrived at they don't seem to know.

In this video, however, a non-flat earther checks the flat earth method and comes up with a figure of 3,594 miles.

He uses places on the equator, on the equinox, where the sun is either 60 degrees east or 60 degrees west at the same time.

I checked his figures and got more or less the same result. Then I tried it with 30 degrees and again found a similar figure of 3,599 miles. But when I tried 45 degrees it was 3,105 miles.

Another fella has a video with some pretty groovy autocadding going on, where he triangulates angles from three cities and comes up with locations for the sun:

His first result gives a height of 3,052 miles, and then he does it again for an hour and two hours later, which gives results of 3049 and 2668 miles respectively.

First conclusive 100% proof that the flat earth sun has a variable altitude!

Another fun thing to do is look at simulations of how the sun actually works on a flat earth. This guy has a video up which demonstrates a program he made to grab longitude/latitude coordinates and create a map. Bit of a roundabout way to arrive at what we already have, but I found it interesting.

He also compares the map his program creates with the flat earthers' beloved Gleason projection map and finds, surprise surprise, that they match up perfectly.

I suppose a switched on flat earther would deduce from this that the Gleason map is actually a projection map after all, and not some secret rediscovered genuine map of the diskworld.

The other thing I like about his video is that, by using sunrise/sunset data, he's plotted what the sun looks like on the projection map, and therefore on the Gleason map too. Again, nothing we didn't already know, but arriving at it in this manner, and then seeing that weird, impossible elliptical/crescent area of light on the flat map is pretty neat.

If I had the knowhow I'd probably make a little video of a year's worth of real sun moving over the Gleason map. Any flat earthers, therefore, could tally it with reality and note that it simply doesn't work.

Yeah, right!

How they explain that the sun goes from illuminating a crescent in January:

To illuminating an ellipse in June:

To a...well, yeah, I'm not sure what kind of shape this is, in March:

is beyond me.

What a magic sun they have! Much better than ours. ;-)

Last edited: Jul 13, 2016
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16. ### The PhaneronNew Member

The size of the sun as it orbits the disc due to perspective is not the only variable here. There is something very significant that they are failing to consider, and it absolutely destroys the theory once and for all. Let's assume that they could somehow explain the sun remaining the same size, so the argument that the sun would change drastically due to perspective is rendered irrelevant. It doesn't matter in the least. Consider the implications of being able to see the sun for up to 12 hours or longer in the first place. Regardless of whether we are showered by it's light or not, the fact that it can be seen for an entire day presents flatties with a huge hole in the model which they outright fail to address. Let's explore how: The sun takes 24 hours to travel around the equator which is 40,008 km in circumference, meaning that it would have to be RACING above our heads at 1,667 kms/hour to make a full rotation (i.e. 1 day).

This means that during 12 hours of sunlight, it would have to travel at least 20,000 km; the equivalent of half way around the disc (and travel significantly longer and faster during the northern winter due to it being closer to the Antarctic perimeter). Take New Zealand for instance: A relatively small southern hemisphere country that is only 450 km wide at it's widest point (Taranaki to Gisborne). During the summer solstice, the longest day in N.Z is 14 hours! And flat earthers state that the vanishing point for sunset is merely a "few thousand kilometers away tops." How is it even remotely possible that a) independent of solar parallax, a local sun of 32 kilometers wide appears in the same point in the sky at noon no matter where you are located in the country, and b) how is the sun visible for 12-14 hours in N.Z when it should be on the opposite side of earth near South America before it even sets (bearing in mind the horizon is roughly only 4.7 km away at sea level)?

In short, the fact that it would have to be on the opposite side of earth and still hasn't set proves that earth must be round. The sun simply wouldn't set on a flat disc. Instead, the lowest it could possibly get is 12.9 degrees above the horizon, but could never pass below it... There would be midnight sun everywhere. Similarly, the Arctic circle would always have a midnight sun, as the sun could never pass lower than a whopping 30 degrees above the horizon!

Every time I ask this question, they respond with silence. They cannot provide me with an answer, let alone a convincing one in the least Instead they dodge it and quickly change the subject. Thoughts??

Last edited: Aug 14, 2016
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17. ### IntiActive Member

To test this, watch a bird flying away from you. Does it appear to become smaller, even though it is rising steadily above you?

Do houses on a mountainside seem the same size as this near you on the plain?

How can people make such claims, s that contradict what we can see around us every day?

18. ### IntiActive Member

You seem to be right, in general principle. However, FE believers often say that the sun circles over the northern, inner region of the disk earth during the northern summer, and further out over the southern ring beyond the equator during northern winter. This implies that the sun's velocity increases in proportion with its distance from the north pole.

For no natural reason, of course, like everything in their models.

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19. ### Hama NeggsSenior Member

I have never understood about this supposed "circling" motion of the Sun. Is it supposedly orbiting something? Just defying all laws of physics?

Last edited: Aug 15, 2016
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20. ### IntiActive Member

I really don't think most FE believers think that laws of physics are real. Unless they get the idea that something might "prove" their case.

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21. ### Hama NeggsSenior Member

So massive objects can just "circle"??

22. ### Bass In Your FaceActive Member

The most common answer I see Flat Earth-ers give, is that the sun and moon are either created by "them", or they are moved by "them" ("them", being NASA or governments or the UN or whatever, that is a variable that changes depending on the person), which usually relates directly to the "dome" of lights pretending to be stars/planets, I see it implied that the sun and moon are attached to the dome in some way, if they are actually a physical object (and not a hologram as many suggest).

23. ### The PhaneronNew Member

I agree. I did mention the fact that it would have to change speed and distance throughout the year, "(and travel significantly longer and faster during the northern winter due to it being closer to the Antarctic perimeter)..." and it makes no sense that it would speed up or slow down, considering they can't even tell us the supposed composition of the sun (if not thermonuclear fusion then what fuels it?), and nor can they tell us the mechanism that drives it's movement in the first place. Flat earthers tend to deny the existence of gravity, so they cannot attribute it as a cause for the sun's orbit. Many flat earthers do not believe that the sun is not attached to the firmament, but rather suspended in the air and free-roaming (despite the fact that the sun moves at the exact same speed as the stars from our perspective). It makes sense that it is not the sky that is rotating. It is the Earth.

Last edited: Aug 15, 2016
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24. ### The PhaneronNew Member

Precisely. See the above reply to Inti

25. ### The PhaneronNew Member

That's the most ridiculous F.E explanation I've ever heard, but unfortunately this primitive idea is propagated by many conspiracy theorists as fact. The sun has been adored as a natural everlasting object for centuries, possibly even millennia. Even the ancient cultures were aware the sun wasn't "man-made." Rather, they considered it an immortal, life bringing deity. It was worshiped as a God by many cultures and religions for many hundreds if not thousands of years B.C., at least until Christianity plagiarized the Egyptian sun God myth and turned the allegory "Horus" into "Jesus." If the sun is artificial, how was it created prior to the development of even the most primitive technology? If not thermonuclear fusion, it must be undergoing exothermic combustion...

And if that is the case, how could it burn for many thousands of years (or 4.6 billion years if you accept the cosmological evidence)? I'm pretty sure that if it utilized an organic fuel source,then- like a massive fire- it would have depleted most (if not all) of it's gas and burnt itself out by now! Physics and photosynthesis tells us that the sun would have to release and churn out millions of times more energy than a synthetic 32 mile-in-diameter shining orb to fuel and initiate every biological process on the planet. Pancake worshipers fail to understand that we have known earth is spherical for roughly 2,300 years- long before the establishment of NASA or the NWO. We don't even need NASA to know that the earth is an oblate spheroid... "They" only provided the images. Lol I really despise the 'pronoun game!'

Last edited: Aug 15, 2016
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26. ### IntiActive Member

Yes; the precise mythology and cosmology seems to vary at the whim of the particular Flat Earth group, but the essential function of flat earth belief is to underpin a complete rejection of all modernity.. And the idea of causation and regularity expressed in laws or models is part of modernist thinking, so it is rejected.

For instance, when they reject gravity, some FEers substitute "density" as an explanation, and I have even been told that "air pressure" makes things fall. But underpinning this is a crude version of Aristotlean physics, where everything seeks to find its proper place. Things fall down because that is where they belong, and ultimately that is by divine command.

Of course, even the more educated never quote Aristotle, because he was a globe earther.

Last edited: Aug 15, 2016
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28. ### RorySenior Member

I know this is off-topic but...huh?

You don't mean the whole weird massively debunked Zeitgeist theory, do you?

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29. ### Globe headNew Member

http://tube.geogebra.org/student/2141849

When I click on this link, it just takes me to the home page for geogebra. I don't know how to find the interactive simulation by David Ridlen.

Btw, excellent diagram on the flat earth measurements and elevations!

32. ### Globe headNew Member

I have a question. In finding any angle of view to the sun from my location on a flat earth,can I use tan-1=o/a?

33. ### Mick WestAdministratorStaff Member

Can you include a notated diagram with questions like this, otherwise it's a bit hard to follow.

35. ### Globe headNew Member

So, my question is for any distance from my location, can I use this formula to figure the angle of view or altitude of the sun over the horizon on a flat earth?

The reason I am asking is because I want to be accurate if I post someone like this on a flat earther site.

Last edited: Jun 15, 2017
36. ### Mick WestAdministratorStaff Member

Yes, assuming light travels in straight lines.

Obviously under normal physics the sun would be constantly visible on the Flat earth.

The FE argument is that "perspective" makes it sink and set. This can obviously be falsified by use of trigonometry (as you seem to be doing), but some people view that as an appeal to authority. They prefer something that looks like a propositional-logic proof over a math one.

That's why I like to open discussions of the sun with noting the unchanging size through the day. Perspective makes things like planes get closer to the horizon. So you'd expect perspective to make the sun get closer to the horizon on a flat earth. However perspective make things get smaller. It makes planes get smaller. It does not make the sun get smaller. Therefore it's not perspective. No math required.

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37. ### Globe headNew Member

The angular size of the sun from 10440 (the hypotenuse of 3000 and 10000) mile distance and 32 miles in diameter is .17°.

The all-magical perspective. It makes a 3000 mile sun fit the current path. it's rises and sets way too fast to be traveling over a FE.

If they want to keep things in perspective, if the earth is 3000 miles below the sun at noon, how far is the earth below the sun at the horizon? Either the sun has gotten very, very close to the flat earth or it's a huge curve or a very fast slope to keep the earth at 3000 miles below, wouldn't you think? Or is that not a valid argument?

38. ### RorySenior Member

Sorry, I don't think it's quite clear what you're saying.

39. ### SvartbjørnSenior Member

Sounds to me like he's saying that at a 90 degree angle from the disk, the Sun is 3k Miles from the surface. For the sun to remain the same size it must either A) Increase its speed from horizontal, to vertical, to horizontal or B) the sun must get SUPER close to the earth in the morning and evening and SUPER far away at noon. If it didnt do one of these things, the perspective would change, the sun's size would change and theyd have to find another explanation with the given that this is occurring on a disk world.

40. ### Amber RobotMember

Their argument doesn't work. It doesn't pass even the mildest of scrutiny and comparison to the real world. But I think Mick put it best when he said, "They prefer something that looks like a propositional-logic proof over a math one." They like the "proof" that *feels* like it agrees with their notion, regardless of the obvious observational consequences.