Is the Earth Really Round?

In Astronomy by Brian Koberlein10 Comments

Whaddya mean?! Of course the Earth is round. It’s so mind numbingly obvious that the Earth is round. It’s an idea we rarely question. But suppose a curious child asked you to prove it. Pointing at a globe or a photograph isn’t enough for this young scientist. She wants to discover that the Earth is round for herself.

The Fata Morgana effect. Credit: Wikipedia

One of the most common demonstrations to support a round Earth is the fact that ships sailing away from shore appear to drop below the horizon as they are farther away. It’s an effect that’s particularly clear with tall sailing ships, but is more difficult to observe with low cargo ships and the like. It also doesn’t always work that way. When observing objects on the far horizon, it can appear that a ship actually rises above the horizon (what’s known as a Fata Morgana). We now know this is due to the refraction of light through the atmosphere, but if light can be refracted upward, who’s to say it couldn’t be refracted downward?

The Eratosthenes experiment. Credit: Julian Rubin

The Eratosthenes experiment. Credit: Julian Rubin

Since refraction is a problem on the horizon, you could measure the Sun at its highest point in the sky at two different locations on Earth. This was first documented by Eratosthenes around 240 BC. He noted that at the solstice the Sun passed directly overhead in the city of Syene, but cast a shadow on the same day in Alexandria.  By measuring the distance from Syene to Alexandria and using a bit of geometry, Eratosthenes not only demonstrated a round Earth, but he also measured its size to within a few percent.

Aristotle's observations of the constellations. Credit: Moriel Schottlender

Aristotle’s observations of the constellations. Credit: Moriel Schottlender

Even before Eratosthenes, Aristotle noted his evidence of the round Earth in “On the Heavens,” written in 350 BC. He noted that when traveling to Egypt that certain constellations seen from Greece could not be seen in Egypt. This was only possible if the surface of the Earth was curved. So if you take your curious scientist on a road trip, you can easily see the Earth is not flat. With a bit of careful measuring you can even get a rough estimate of its size.

The round shadow of Earth against the Moon.

The round shadow of Earth against the Moon.

If you’re not able to travel, one other way you can see evidence of a round Earth is through a lunar eclipse. It just so happens that there’s a lunar eclipse at the end of this month. As the shadow of the Earth passes over the Moon, you’ll notice that the shadow of the Earth is circular. This is always the case, whether the Moon is near the horizon or high overhead. The Earth’s shadow is always round. Perhaps it’s just an optical illusion, but that’s very unlikely. Observations of lunar eclipses were used to argue in favor of a round Earth for centuries before the measurement of Eratosthenes.

So we’ve known that Earth is round for a very long time. What’s interesting about this question is that it shows how careful observations can lead to an amazing discovery, and how a confluence of evidence can build to support a scientific idea. From our modern perspective a round Earth is obviously true, but it was once hard-won knowledge. But even now we don’t need to rely on past authority to support long-standing scientific ideas. We can always go back and prove it for ourselves.


  1. Only the brain washed believe in a round earth. They refuse to study for themselves and be zetetic and prove if those things are so.
    The faked globe earth is because of hatred towards God. Copernicus hated God, and without any proof he claimed a globe earth, even though most cultures all had a flat earth model.
    Since the Devils in the catholic cult could not stop the printing press, they had to devise fake science to dumb down the people.
    Besides, the bible shows the earth to be flat. Some 200 verses of obvious proof.
    Ships disappearing past the horizon. First off, it is called sea LEVEL for a good and obvious reason, as is so with the HORIZON, not the CURVISON. Hello! Next AFTER that ship or ANY ship disappears from sight, try binoculars or a telescope and you will be shown to be a liar supreme.
    It is nothing but perspective.
    The same faked globe earth with stars can just as easily be shown to be from a flat plain. One can see many videos on this very topic.
    Off the coast of Powell river are a couple of islands some 5 to 6 miles away. Texada and Harwood islands. According to the faked globe theory the curvature for that length should be some 16 to 24 feet. But we all can see the waves lapping the shores of Texada from out own shore in Powell River.
    See how they lied to you with the fake globe in the class room? They want to make you their prisoner.
    Isn’t it interesting that we never ever see a supposed satellite flying past the moon? And the fake pictures of the earth are all CGI. From NASA, who started the same year the ANTARCTIC treaty was put in place. How come no thousands of satellites in the sky? because iot is a lie. The sun and moon are close. The moon does not get its shadow from the earth as the moon is very small and is only a few thousand miles away or closer.
    Plus, In the recent history of star gazing, there have been at least 50 accounts of BOTH sun AND moon in the sky in our vision AT THE SAME TIME.
    Plus the moon has a daily circuit but the tides have double that as it gets at least TWO high tides per 24 hours.
    You have been lied to and ya actually believed it, like I did at times, when not truly concerned.
    Faked NASA with swimming pool pictures instead of actual space.
    That is because the earth has a dome over it called the FIRMAMENT.
    There is no outer space. This is ungodly people telling you lies of your world and of you.
    They are hiding God and his creation from you
    Think about it, and prove if these things are so.
    Peter Fuhrman

    1. Why do you feel that science and a round globe would disprove God? If anything the sheer magnitude of space, the wonder there is to be seen trough science reveals an even greater, more miraculous creation. God and sciense are not mutualy eksclusive! In fact, plenty of astronomers and nuclear physisist are religious. You don’t hear the Pope aguing for a flat earth and he has his own telescope. Why do you seek to limit God in this way? You are making Him smaller by insisting that a group of people writing tekst 2000 years ago knew everythin there is to know about the wonderful earth we live on, when there is so much more to know, so much more to see! You are missing out big time!

  2. lee,
    wow, what an awesome rebuttal of the evidence peter cited and directed people to examine for themselves

    all we need are personal attacks and science has been achieved

    look at bill nye, a character from a skit tv show
    but multitudes believe he is a real scientist

    indoctrination is not science, science is and always will be examination of our physical world

    prove it to yourself,
    don’t let others indoctrinate you

  3. Nah, the earth is flat. Anyone who does their own research instead of drinking the koolaid of fake scientist hacks like Bill Nye and just blindly accepts whatever is thrown at them in the name of science (which is actually pseudoscience) and does so with an open mind and not with a confirmation bias that the earth is round, they will see the earth is indeed flat. Any and every “proof” for the globe earth joke has been debunked. Don’t believe me? Then do your research, kiddos.

  4. Truth will set you free! And believing that water sticks to a ball,ridiculous! The blind leading the blind. Even those who do not believe in THE CREATOR, can never make free flowing water mold around a ball, Heavens are above the earth and Hell is below it, vast and wide where many devils will end up for lying and teaching falsehood about CREATION. A flat, Square, triangular, pear-shaped earth does not bring salvation; But The Almighty tells us to seek wisdom and tells us that people perish for lack of knowledge. You can never prove HIM wrong as HE is who created it all. Try and go find out all the pics from NASA are fake.
    Nobody is spinning on a ball, ludicrous! Hahaha

    1. Author

      Fun fact, for most of the Christian era the the Church has held that the Earth is round. During the Protestant reformation, protestant churches claimed that the Catholics held that the Earth is flat as a way to disparage them. The idea of a flat Earth really came to popularity among Christian fundamentalists in the early 1900s, largely in connection to opposition to Darwinian evolution (i.e. the Scopes Monkey Trial, etc.) So historically Christian cosmology has had a round Earth.

      On the other hand, Norse mythology did envision a flat Earth with the world tree Yggdrasil in the center. So maybe you’re right, and we should all accept our CREATOR, praise Odin!

  5. Why are we still asking if the earth is round when a guy proved it hundreds of years ago with a stick in the ground. People claim the world is flat and science is bullshit, and do this on the internet using a cellphone or a computer… How exactly were those things created?

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