Top 10 Ways to Know the Earth is Not Flat

A few months ago I released an experiment video explaining how Eratosthenes calculated the circumference of the Earth using the shadow of sticks. The method was performed almost two millenia ago, and produced quite accurate results (considering the ‘equipment’ used). But it was far from being the only (or first) method to understand our planet’s shape.

Humanity has known the Earth to be round for a few millenia and I’ve been meaning to refine that video and show more of these methods of how we figured out the world is not flat. I’ve had a few ideas on how to do that, but recently got an interesting incentive, when Phil Plait (The Bad Astronomer) wrote about a recently published BBC article about “The Flat Earth” society. Phil claims it’s ridiculous to even bother rebutting the flat earth society – and I tend to agree. But the history of our species’ intellectual pursuit is important and interesting, and it’s very much well worth writing about. You don’t need to denounce all science and knowledge and believe in a kooky conspiracy theory to enjoy some historical factoids about humanity’s quest for space.

Though I have researched this subject, I am quite certain there will be much more to be said about it – feel free to add more in the comments. If all goes well, this might actually be a good post to refer to whenever anyone wants to discuss a bit of ancient science and the source of cosmological thought.

On we go to the top 10 ways to know the Earth is unequivocally, absolutely, positively, 100% not flat:

(1) The Moon

Now that humanity knows quite positively that the Moon is not a piece of cheese or a playful god, the phenomena that accompany it (from its monthly cycles to lunar eclipses) are well-explained. It was quite a mystery to the ancient Greeks, though, and in their quest for knowledge, they came up with a few insightful observations that helped humanity figure out the shape of our planet.

Aristotle (who made quite a lot of observations about the spherical nature of the Earth) noticed that during lunar eclipses (when the Earth’s orbit places it directly between the Sun and the Moon, creating a shadow in the process), the shadow on the Moon’s surface is round. This shadow is the Earth’s, and it’s a great clue on the spherical shape of the Earth.

Since the earth is rotating (see the “Foucault Pendulum” experiment for a definite proof, if you are doubtful), the consistent oval-shadow it produces in each and every lunar eclipse proves that the earth is not only round but spherical – absolutely, utterly, beyond a shadow of a doubt not flat.

Refer to the following image from Wikipedia for more details on what happens during a lunar eclipse:

Click for the Original

Click for the Original

(2) Ships and the Horizon

If you’ve been next to a port lately, or just strolled down a beach and stared off vacantly into the horizon, you might have, perhaps, noticed a very interesting phenomenon: approaching ships do not just “appear” out of the horizon (like they should have if the world was flat), but rather emerge from beneath the sea.

But – you say – ships do not submerge and rise up again as they approach our view (except in “Pirates of the Caribbean”, but we are hereby assuming that was a fictitious movie). The reason ships appear as if they “emerge from the waves” is because the world is not flat: it’s round.

Imagine an ant walking along the surface of an orange, into your field of view. If you look at the orange “head on”, you will see the ant’s body slowly rising up from the “horizon”, because of the curvature of the Orange. If you would do that experiment with a long road, the effect would have changed: The ant would have slowly ‘materialized’ into view, depending on how sharp your vision is.


(3) Varying Star Constellations

This observation was originally made by Aristotle (384-322 BCE), who declared the Earth was round judging from the different constellations one sees while moving away from the equator.

After returning from a trip to Egypt, Aristotle noted that “there are stars seen in Egypt and [...] Cyprus which are not seen in the northerly regions.” This phenomenon can only be explained with a round surface, and Aristotle continued and claimed that the sphere of the Earth is “of no great size, for otherwise the effect of so slight a change of place would not be quickly apparent.” (De caelo, 298a2-10)

The farther you go from the equator, the farther the ‘known’ constellations go towards the horizon, and are replaced by different stars. This would not have happened if the world was flat:

(4) Shadows and Sticks

If you stick a stick in the [sticky] ground, it will produce a shadow. The shadow moves as time passes (which is the principle for ancient Shadow Clocks). If the world had been flat, then two sticks in different locations would produce the same shadow:

But they don’t. This is because the earth is round, and not flat:

Eratosthenes (276-194 BCE) used this principle to calculate the circumference of the Earth quite accurately. To see this demonstrated, refer to my experiment video about Eratosthenes and the circumference of the earth – “The Earth’s curvature is tasty!“.

(5) Seeing Farther from Higher

Standing in a flat plateau, you look ahead of you towards the horizon. You strain your eyes, then take out your favorite binoculars and stare through them, as far as your eyes (with the help of the binocular lenses) can see.

Then, you climb up the closest tree – the higher the better, just be careful not to drop those binoculars and break their lenses. You then look again, strain your eyes, stare through the binoculars out to the horizon.

The higher up you are the farther you will see. Usually, we tend to relate this to Earthly obstacles, like the fact we have houses or other trees obstructing our vision on the ground, and climbing upwards we have a clear view, but that’s not the true reason. Even if you would have a completely clear plateau with no obstacles between you and the horizon, you would see much farther from greater height than you would on the ground.

This phenomena is caused by the curvature of the Earth as well, and would not happen if the Earth was flat:

(6) Ride a Plane

If you’ve ever taken a trip out of the country, specifically long-destination trips, you could notice two interesting facts about planes and the Earth:

  • Planes can travel in a relatively straight line a very long time and not fall off any edges. They can also, theoretically (and some do, though with stops along the way), circle the earth.
    Correction (Courtesy of Klaynos, from Apparently, planes can circle the Earth without stopping!
  • If you look out the window on a trans-Atlantic flight, you can, most of the times, see the curvature of the earth in the horizon. The best view of the curvature used to be on the Concorde, but that plane’s long gone. I can’t wait seeing the pictures from the new plane by “Virgin Galactic” – the horizon should look absolutely curved, as it actually is from a distance.

(A picture of the curved horizon from a Concorde plane can be seen here).

(7) Look at Other Planets

The Earth is different from other planets, that much is true. After all, we have life, and we haven’t found any other planets with life (yet). However, there are certain characteristics all planets have, and it will be quite logical to assume that if all planets behave a certain way, or show certain characteristics – specifically if those planets are in different places or were created under different circumstances – our planet is the same.

In other words: If so many planets that were created in different locations and under different circumstances show the same property, it’s likely that our own planet has the same property as well. All of our observations show planets are spherical (and since we know how they’re created, it’s also obvious why they are taking this shape). Unless we have a very good reason to think otherwise (which we don’t), our planet is very likely the same.

In 1610, Galileo Galilei observed the moons of Jupiter rotating around it (click here to see a beautiful video reconstruction of his observations). He described them as small planets orbiting a larger planet – a description (and observation) that was very difficult for the church to accept as it followed a geocentric model where everything was supposed to revolve around the Earth. This observation also showed that the planets (Jupiter, Neptune, and later Venus was observed too) are all spherical, and all orbit the sun.

A flat planet (ours or any other planet) would be such an incredible observation that it would pretty much go against everything we know about how planets form and behave. It would not only change everything we know about planet formation, but also about star formation (as our sun would have to behave quite differently to accustom a “flat earth” theory), what we know of speeds and movements in space (like planets orbits, and the effects of gravity, etc). In short, we don’t just suspect that our planet is spherical. We know it.

(8) The Existence of Timezones

The time in New York, at the moment these words are written, is 12:00pm. The sun is in the middle of the sky (though it’s hard to see with the current cloud coverage). In Beijing, where Michael Phelps is likely getting ready for yet another gold medal, it’s 12:00am, midnight, and the sun is nowhere to be found.

In Adelaide, Australia, it is 1:30am. More than 13 hours ahead. There, the sunset is long gone – so much so, that it’s soon going to rise up again in the beginning of a new day. Here’s a list showing what time it is around the world when it is 12:00pm in New York city.

This can only be explained if the world is round, and rotating around its own axis. At a certain point when the sun is shining on one part of the Earth, the opposite side is dark, and vise versa. That allows for time differences and timezones, specifically ones that are larger than 12 hours.

Another point concerning timezones, the sun and flat/spherical Earth: If the sun was a “spotlight” (very directionally located so that light only shines on a specific location) and the world was flat, we would have seen the sun even if it didn’t shine on top of us (as you can see in the drawing below). The same way you can see the light coming out of a spotlight on a stage in the theater, even though you – the crowd – are in the dark. The only way to create two distinctly separate timezones, where there is complete darkness in one while there’s light in the other, is if the world is spherical.

(9) The Center of Gravity

There’s an interesting fact about mass: it attracts things to it. The force of attraction (gravity) between two objects depends on their mass and the distance between them. Simply said, gravity will pull toward the center of mass of the objects. To find the center of mass, you have to examine the object.

Consider a sphere. Since a sphere has a consistent shape, no matter where on it you stand, you have exactly the same amount of sphere under you. Imagine an ant (perhaps the same one from the previous point) walking around on a crystal ball. Assuming the crystal ball is polished, the ant’s only indication of movement would be the fact it’s moving its feet. The scenery (and shape of the surface) would not change at all.

Consider a flat plane. The center of mass of a flat plane is in its center (more or less – if you want to be more accurate, feel free to do the entire [shriek] integration [shriek] process), and the force of gravity will pull a person toward the middle of the plain. That means that if you stand on the edge of the plane, gravity will be pulling you toward the middle, not straight down like you usually experience.

I am quite positive that even for Australians an apple falls downwards, but if you have your doubts, I urge you to try it out – just make sure it’s nothing that can break or hurt you. Just in case gravity is consistent after all.

Further reading about the center of mass and about distribution of mass can be found here. And if you are brave enough to handle some equations (not involving integration), you can learn some more about Newton’s Law of Universal Gravitation.

(10) Images from Space

In the past 60 years of the space exploration era of humanity’s history, we’ve launched satellites, probes and people to space. Some of them got back, some of them still float through the solar system (and almost beyond it) and transmit amazing images over to our receivers on Earth.

Here’s a list of some of the pictures we’ve seen from space throughout the years:

October 24, 1946: A group of scientists in the New Mexico desert saw the first grainy photo of the Earth. The photograph was taken from a height of 65 miles (104.6 kilometers) by a 35-millimeter motion picture camera riding on a V-2 missile.

August 14, 1959: First crude photo of the Earth from the Explorer VI satellite. The photo showed a sun-lit area of the Pacific ocean and cloud coverage. It was taken from about 17,000 miles (27,350 kilometers) above the surface.

(Image Courtesy of the NASA GRIN Website)

June 5, 1966: Astronaut Eugene Cernan took this amazing picture of Gemini 9 and the Earth during his EVA (Extravehicular Activity). The spacecraft itself and Cernan’s “umbilical” (the cord that keeps him connected to the spacecraft’s systems) are visible on top of a beautiful background of the Earth.
(Image Courtesy of the NASA GRIN Website)

August 23, 1966: First view of Earth from the Moon. This picture was taken by Lunar Orbiter I when the spacecraft was on its 16th orbit and was just about to pass behind the Moon. (Image Courtesy of the NASA GRIN Website)

December 29, 1966: A spectacular view of the rising Earth from the Moon, taken by the crew of Apollo 8 after coming out from the other side of the Moon, approximately 239,000 miles (384,000 kilometers) from Earth.

(Image Courtesy of the NASA GRIN Website)

December 1, 1968: Photo of Earth from Apollo 8. This photograph was taken by an 80-mm lense, at a point very close to the Moon.

(Image Courtesy of the NASA GRIN Website)

More pictures from the NASA Missions throughout the years can be found at NASA GRIN Website:

Brief List of Manned Missions to Space

In the past 60 years humanity’s quest for Space has produced hundreds of pictures, videos and audio records from more than just the United States. Some of these countries used to be enemies. Some still are. The amount of proofs, from opposing countries and ‘sides’, for the non-flatness of the Earth, if nothing else, should cast serious doubt on any possibility for the existance of “Global Conspiracy”. Here is an abbreviated list of some of the first missions to space:

  • April 12, 1961 (USSR; Vostok-1): Yuri Gagarin, becomes first man in space.
  • May 5, 1961 (USA; Mercury-3): Alan Shepard becomes first American in space.
  • July 21, 1961 (USA; Mercury-4): Gus Grissom performs the second sub-orbital flight at an altitude of 126 miles (203 kilometers).
  • August 6, 1961 (USSR; Vostok-2): Gherman Titov becomes the first man to spend an entire day in space.
  • February 20, 1962 (USA; Mercury-6): John Glenn orbits the Earth at a distance of 100-162 miles (161-261 kilometers).
  • May 24, 1962 (USA; Mercury-7): Scott Carpenter orbits the Earth three times.
  • August 11, 1962 (USSR; Vostok-3): Andrian Nikolayev leads the first four-day flight, and first “group” flight with Vostok-4.
  • August 12, 1962 (USSR; Vostok-4): Pavel Popovich mans the other half of the “group” flight with Vostok-4.
  • October 3, 1962 (USA; Mercury-8): Walter Schirra orbits the Earth six times.
  • May 15, 1963 (USA; Mercury-9): Gordon Cooper pilots the longest (and last) Mercury mission, lasting 34 hours in space.
  • June 14, 1963 (USSR; Vostok-5): Valery Bykovsky is the first to stay 5 days in space.
  • June 16, 1963 (USSR, Vostok-6): Valentina Tereshkova becomes the first woman in space, spending three days in orbit.

You can find a full list of the chronology of manned space missions at the University Corporation for Atmospheric Research.

More Methods Throughout History

  • Abu Rayhan Biruni (sometimes known as “The Father of Geodesy“), has managed to calculate the circumference of the Earth using complex triangulation equations. I couldn’t find the actual calculation, or the method, so I can’t judge it this as a relatively easy “DIY” way to do it, but it’s still worth mentioning. If anyone has any more information about the method used, do post in the comments.
  • Bedford Level Experiment: At the Bedford river in Norfolk, England. The experiments were done initially in order to prove that the Earth is flat. Though the first results of this experiment seemed to agree with the flat-earth contention, later attempts to repeat this experiment agreed with the fact that the Earth is, in fact, spherical.
  • A Bit of History: Neil Armstrong narrating this video of the Earth as viewed from the Apollo 11 Command Module on its way to the Moon.

Credits and Thanks

This is a very long post, but it was fun to write (and learn about!). There is some credit due to other people, and I am not one to hold out the cheers:

  • Klaynos, from scienceforums, for his Physics mastery late at night.
  • insane_alien from scienceforums, for directing me on the path of a good #9.
  • Cap’n Refsmmat from scienceforums, for clarity issues, physics help, and saving you (the reader) some of my ramblings.
  • Keren, for her editorial help and general (good) advice.
  • Daniel and KerenG, for their mental and grammatical support.

Extra Resources


The earth we are told has a diameter of @8,000 miles or roughly 40 million feet.  Times 3.14 for the earth circumference is @ 125 million feet.  A line from either pole to the equator is thus one quarter of the circumference or @ 32 million feet.  A line from either pole to the equator descends below the pole 4,000 miles or 20 million feet. Thus, for each foot from a pole to the equator there is a descent of roughly 2/3 of a foot.  Thus, a mile and a half from the pole there is a descent of of @ 1 mile according to these calculations. 

This is not what we see here on earth.  In Los Angeles, for example Catalina Island is 26 miles off shore but is visible to the naked eye most days.  According to the calculatons above we  should not be able to see Catalina Island.  Catalina should be miles below the horizon.  How can this be unless the earth is not spherical?

This simple calculation must be explained in order for the spherical earth theory to remain viable.


If the earth is spinning on its axis while orbiting around the sun, then you couldn't have the polaris rotation. Since the polaris rotation is real you can't have a spinning rotating earth. That's one huge score for the flat earth model (geocentricity) team.

Discovery Boii
Discovery Boii

The earth is not round, it's spherical, if u say round u speak of a 2 dimensional object.


If the earth was flat there would been an ending point on the earth


I hate how people say the phrase, "Round Earth Theory" it is not a theory it is a fact that the earth is round. Flat Earth THEORY believers are ignorant and refuse to listen to reason. So basically Flat Earth THEORY people believe that all the world's governments and science authorities lied to everyone for almost no reason, and that all the astronauts and everyone who works at NASA are lairs who are hell bent on spreading the idea that the Earth is round.  Oh yeah and everyone who has ever piloted and airplane is in on the conspiracy too.     


Oh, and FET, or Flat Earth Theory, is written a lot in these parts. "Conjecture," would be the more accurate term.


I’m struggling to believe that the picture shown at:

… was actually taken from a Concorde (cruising height approx 11 miles according to that page).

Doesn’t the curvature in that image look greater than in another picture you link to:

… which was “taken from an altitude of 65 miles”, according to that page?

I think the sciencemuseum pic is just there to illustrate the curvature of the Earth – their text is arguably misleading. (And if they’ve changed the picture since you linked to that page, fair enough!)


@SB, that’s a good point, I found that picture on the museum’s site, but that was after I have read in a few places that you can see the curvature of the Earth from the concorde.


Critical thinkers, we got here: Focal length. Cropping. Seemingly, the very fundamentals of photography, and simply, imagery (with lack of description), elude you.


great it really helped in my science essay so thanks and i really appreciate it thanks for making a great website i will recomend it to me friends!!!!!!!!!!!!!!!!!!!!!!!!!


i love this site coz it gives a lot of info we need

Rikard Nilsson
Rikard Nilsson

I only glanced over the page but I think you forgot the simplest one of all:

Start walking in one direction, when you reach your starting point you've disproven that the earth is flat.

John D de Vries
John D de Vries

I wonder...

If I take a photograph of the horizon with a wideangle 105 deg at eye level (1.75m)

Wkat would be the width of the horizon covered on my final image in km

Thanks in advance,

John d de Vries

Todd G
Todd G

The joke is on everyone who is bothered by or spends time trying to refute the Flat Earth Society. Nicely played, FES, nicely played. ;-)


I would like to point out a few flaws in the arguments against a flat Earth provided.

FET = Flat Earth Theory

RET = Round ' '

1) This starts with the assumptions that the the darkening of the Moon is a shadow, and that it is of the Earth. Two things that need to be supported.

2) Ships dipping below the horizon can be explained.

There have been cases where using a telescope has been able to restore parts of the hull that were "hidden"

4) The assumption "If the world had been flat, then two sticks in different locations would produce the same shadow" is not backed up and is contrary to what would be expected in modern FET.

6) Circumnavigation can be explained in FET. You travel in a circle around the Earth, just like in RET.

7) This a form of begging the question. You are assuming the Earth shares enough qualities with other celestial bodies so that they can be classified together. You then use that as an argument to show that the Earth shares properties with other celestial bodies.

8) The Sun travels in a circle along the equator. When the Sun is directly overhead an area, it is noon. Noon is at different times in different areas, ergo time zones are explained.

9) Gravity as we know it does not exist in FET. The Earth accelerated upwards.


We actually account for all of this, as you might have discovered had you researched FET as thoroughly as you did RET.

Alivia Hooper
Alivia Hooper

Christian Dillstrom had a book mark to your post. Any idea why? Mobile + social media marketing virtuoso's do not recommend something without a reason.


Well... I can see someone's been successfully trolled... Seriously, there's no point in arguing with these people. It's like arguing with the DHMO people, or YouTube commentators. Honestly, they're just trying to get attention and reaction.



Gilles Feyrit
Gilles Feyrit

Congratulations for this brilliant & crystal clear compilation of centuries of human doubt & deductive thinking!


what's the distance in kilometer if a man with the height of 1.7m stand on sea to the point of the sightview limit of the earth's curvature?



You didn't get my last question clearly otherwise you would have understand that I believe Darwin's evolution is also wrong. That's what I am saying, I am discarding both because they use the same scientific methodology namely near-sighted.

Flat earth was very evidence at their time and knowledge. If someone never traveled far at their time, skies to them were more understood as mythology than coordination of the planets. The ground of their great empire underneath them was flat because their measurement of "their flat earth" was limited by their thinking and knowledge. They were probably right at their time and place, but the earth underneath them does not represent the Earth we known today. Because our knowledge of sky today is beyond our own planet.

Change the "earth" into "time" and expand it in the above explanation, you would understand why Darwins theory of evolution is the flat earth equivalent of the formation of living things on earth.

Would someone understand Darwin's theory of evolution answer my above question why primates choose to be primates rather than humankind after millions of years. If people believe their ancestors are apes, why then their scientific name is different from us. Why didn't apes classify as homo sapiens?

Why is it there's a huge difference between the intellectual level of human and primates? Ok, The answer is the brain. But what makes brains of different species so different if they all originated from single cell organism living on the same earth for millions of years?

What determine the branching of species among highly intellectual species? Why can't you find a living example of apes at the transition stage into human somewhere in the secluded forest?

Until today those believe in Darwin's evolution still can not resolve the missing link and they just come out with whatever conjecture. Trying whatever unfounded bits and pieces trying to fill the missing link Otherwise they would not call it the "missing link" but some terms more concrete.


Well, with a powerful telescope, a gigantic ship so that the size of the ship compares to the earth is proportional to an ant to an average size orange. Then, it's a different story.


Flat earth is certaily stupid but evolution is only partially true and many fallacies equate part to whole. Can you explain the following with evolution?

"Considering the long existent of primates on earth, they are good in mimicking, able to use tools and the fact that they have so much similarities with human genes? Being human certainly has the advantage over primates.

Q. Why don't they choose to evolve into human beings like us instead of evolved into primates if they were once your ancestors? The answer can only accepted with proven science. Therefore do not answer with intelligent design?


@nick100 Your calculation has an error. The earth's surface curves at ~8 inches per mile. Also, the island isn't flat, it's sticking out of the ocean with its highest point at 2,096 feet.

Using correct calculations, you can see approximately 1,600 feet of Catalina island (from the horizon to the peak of Mount Orizaba) from 26 miles away - i.e., the mainland. If the island were to "drift" away, the peak would disappear behind the horizon at approximately 59 miles

So from the mainland you can easily see a portion of the island. Just do the research...


@Rikard Nilsson no, it just means one of your legs is longer than the other and you've just walked in a circle.


@Harutsedo If the earth is constantly accelerating upwards, it shouldn't be long before we're all in heaven.


@Alivia Hooper,

I don't know, I would like to believe he liked the post. Otherwise, I'd ask him ;)


I am not surprised such a web site about flat earth theory exists nowadays.

Our society are full of those kind of people. They are the average class in a society. Imagine if everyone are smart like you guys, I am sure you won't be able to get the affordable services/products you are enjoying now.

Just get any celebrity, someone persuasive to tell some stupid things that appears to be turth, chances are you will get a bunch of followers. To the wise people, "Partial Truth" appears to be truth but is not exactly truth.




From what I've come to know, species evolve as species, not a single organism at a time. We don't find half-evolved chimp/humans in the rainforest because we ARE the evolved and evolving creatures. Every species that exists today is in the product as well as in the process of evolving. Difference in similar species such as the different classifications of Homos are due to separation of some sort in time for a long period of time, be it geographic or social. They became separated and evolved so differently that they became separate species. But there are no members 'left behind' evolution-wise according to this theory. This is just the most widely accepted theory in science.

I'm a creationist but I've done a lot of research from either point of view and I find it all fascinating :) I hope this helps


If people believe their ancestors are apes, why then their scientific name is different from us. Why didn’t apes classify as homo sapiens?

Genetically speaking, you want the work Chimps, and to be technical, the Bonobo. That's like asking why we don't call dogs feline or birds canine. They aren't the same thing, and unless you've been hanging out in a jungle eating bugs from your family, then I don't think you're a chimp. Primates are part of the family Hominidae, with Gorillas (gorilla), Humans (homo), and chimps (pan) all being part of the same sub family. The genus seperation is for pretty obvious reasons.



Evolution is very well evidenced in science, not just history. The only "missing links" the theory has are the same "missing links" a ladder might have in between its steps - that is, there are no missing links. Everything we find in geology, physics, history, chemistry and biology fits absolutely perfectly to the validity of the theory. Interestingly enough, whenever a new evidence is found to support the theory (hence, a new "filling" to a previous "missing link") it serves to strengthen the theory further, but also create two more missing links "before it" and "after it".

But those aren't really missing links, are they?

Furthermore, it seems interesting that you decidedly claim that flat earth is wrong because of scientific evidence, but choose to ignore the same methodology used and state that evolution is wrong. Both explanations are evidenced in science, through the scientific method. If you accept the methodology, they're both quite well evidenced.

If you discard one, shouldn't you discard ALL theories that use the scientific method? Otherwise, what system do you use to differ between the theories that are "correct" and those that aren't, other than personal bias? How do you get rid of personal bias and treat reality objectively facing theories that you like and dislike?

The scientific method is meant to get rid of as much bias as possible in a situation where human beings (who are prone to biases) are doing the research. If you decide to toss that methodology aside, you will encounter problems with biases in your view of reality. How do we learn about objective reality and toss our personal biases aside?



@nazzer @nick100 

tangent 90 degrees to the radius gives vaying results when the length of
the tangent is increased.   A tangent of 10, 100, or 1000 will bring a
curvature much greater than when using 1 mile tangent.   Chord sagitta
works better.

2//3 of the curvature of a circle or circumference from a tangent  accounts
for 1/2 the descent of the circumference along the radius from the
tangent.  Thus, the final 1/3 of the circumference accounts for 1/2 of the
descent of circumference along the radius.  This is a peculiar aspect of a
circle.  Lots of peculiar aspects of the earth hiding in plain sight.

The earth is a sphere. Everyone knows that.  The earth does have some

For example, The nile river is over 4,000 miles long and is the longest
river on earth.  Strangely, it is one of the few rivers that flows south to
north uphill and it flows through a desert with very few feeder rivers.
The curvature of the earth seems to have no effect on the nile river.

My research shows your method of calculation does not work.   The curvature
of an 8,000 mile diameter sphere is much greater than 8" per mile.


There are still people who never leave their hometown their entire life who can esily believe the earth is flat. It's hard and a waste of time to convince them otherwise.


OK, I made a mistake in the sentence "Why is it there’s a huge difference between the intellectual level of human and primates?" I was trying to say human and other primates according to your scientific definition.

The key point I was trying to say are:

1 Humans and apes are from different ancestors even they appear to be similar in the eyes of some scientists. If your scientific knowledge insists you and chimps or bonobos are of the same family or sub family, you are welcome to believe so but we are pretty sure our ancestors were not coming from the same family as the chimps and bonobos. Please don't ask me why.

2. Science may not be 100% correct. Sometimes they are just the theory of a handful scientists who happened to know more than the majority. Time and time again many so called scientific facts had turned out to be wrong. E.g. are the flat earth theory in the old days, Pluto as a planet, etc. The more powerful tools and data we got, the more we get closer to the truth.



Just a question, what do you believe to be the strongest evidence behind evolution?


@nick100 @nazzer The curvature is 8" per mile, it's just that the calculation is parabolic. If you move that 1 mile, the earth will curve another 8" for another mile FROM your new starting point. From your initial starting point though, the drop of course is greater than 8"; it is in fact 32". Basic mathematical principles, does this make sense?


@nick100 @nazzer Just think for moment... you said, "Thus, for each foot from a pole to the equator there is a descent of roughly 2/3 of a foot.  Thus, a mile and a half from the pole there is a descent of of 1 mile according to these calculations." That sounds like a steep hill to me. A person with average height can see about 3 miles to the horizon. And the Nile flows uphill??? No, the higher ground is in the south.


I thought that's what I did... is there any "proof" for the flatness of the Earth that disproves all the points I made? Do show, if there is.


@nazzer @nick100 

Maybe the issue is semantic. 8" per mile is not enough to account for the traverse of the circumference along the radius or 4,000 miles.

Did you try your equation with the tangent at 100 miles or a 1000 miles?  The longer the tangent the greater the difference above the earth.  Inconsistent results.  The traverse of a circumference along the radius starts slow and increases dramatically near the end of the radius.   We know a traveler following the radius to a tangent will traverse 4,000 miles along the circumference relative to the radius.  That's a big drop and a lot of curve most dramatic near the end of the radius because of the nature of a circle.  Your quote above needs to account for this unique aspect of a circle. 

My question about the nile was in regards to the curvature of the earth and the impact the curvature should have on the nile.  the height of the land does not compensate for the curvature of the earth.  

Think of it in miniature.  A 2 foot beach ball with a 1/16 inch raised secion from half way down the beach ball more less like the terrain the nile flows upon.  What would happen if a 1/32 " flow of water was put on that raised section?  It would not move towards Cairo because the curvature of the beach ball would cause the water to flow downfill towards the source of the water.


@nick100 @nazzer You didn't understand, that's okay... . The curvature of the earth has no or little impact on the Nile, gravity affects the flow; hence, high ground to low ground. Earth has radial gravity (it is a planet after all), it's not linear O.o what is this nonsense about a beach ball?


@nick100 @nazzer You just have to think of the 8"/mile thing as parabolic in nature. If you don't move: after one mile, each consecutive mile is going to cause a greater increase in "drop" relative to your initial starting position. However, If you move, the tangent also moves; the angle changes.

You take care too.


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