Almost everyone knows that the Earth is a sphere. Someday, we’ll be able to  drop the “almost” from that sentence.  Unfortunately, today is not that day. Two different flat Earth societies have now raised enough money for billboards.  First, “The Infinite Plain Society” put up a billboard outside of Philidelphia that says “Research Flat Earth”. Soon afterwards, “The Flat Earth Society”, which somehow has over 80,000 likes on Facebook, probably not all of which are ironic, put up a billboard in Oklahoma that asks the question “Is the Earth flat?”

Just to be clear, the answer to this question is a very definitive “no”.

At UYBFS, we have written about the flat Earth people before. However, the billboards are a distressing new twist to this sad story. The folks at The Flat Earth Society are even claiming to be “persecuted” for their beliefs. “We get accused of being idiots, of doing it for money,” lamented Bob Knodel, a flat-Earther from Denver.

Everyone in this country has the right to “believe” what they want and flat Earthers have the right to talk about their theory too.  However, I think persecuted is the wrong word here. Flat Earth is not a religion, a way of life, or value system. It is a statement of implied fact: “I believe the Earth is flat.”

There is inherently no difference between this statement and saying “I believe that clouds are made of spaghetti”. Both are statements made implying that the author has weighed the available data and is drawing a conclusion. Not only are both wrong, but they are just as easily refuted. You can look up at the sky and see there is no spaghetti (Cloudy with a Chance of Meatballs is just a movie), just like you can look at the literally millions of photographs of the Earth and see it is not flat. The willingness to believe that there is a massive conspiracy involving the fabrication of a moon landing, gravity, long distance flight and sea travel, satellite communications, and the millions of PICTURES of the Earth is not a value system to be protected. In fact, it demands action from those of us willing and able to educate.

We at UYBFS are not fans of calling people “idiots” – any adult person who possesses the mental capacity to hold a discussion about the shape of the Earth is inherently smart enough to understand the facts demonstrating that it is a sphere. The issue here is education, so let’s do some educating!

In the spirit of education, UYBFS will answer any and all “proofs” that the Earth is flat with actual science. We’ll do it point by point, starting with some of the most common “proofs” today and and continuing as long as needed until either we run out of proofs to refute or the billboards come down! If you know of any flat Earth proofs we have missed, please add to the comments below. If you actually think the Earth is flat, tell us why, and we can help set the record straight. Let’s do this!

PART I.  THE MOST OFTEN CITED FLAT EARTH PROOFS

1) The Horizon Proof. The horizon always appears flat except for the fake NASA photos. It’s even flat when seen from a plane. 

This is an easy one to start. The problem here is one of perspective. The Earth is a very big sphere, so it is difficult to get high enough to see the curvature of the horizon. You have to be at least 35,000 feet above sea level to see this effect, which means there is no way you’ll ever see it from a mountain. Even in a plane, you need a pretty wide view of the horizon (meaning it’s hard to see it from a passenger window) and it helps to have a very clear day. You’ll find some good videos taken from planes clearly showing the Earth’s curvature here and here. Plus, here’s a picture taken from the cockpit of a plane at 40,00 feet:

But if you are talking to a flat Earther about this theory, you may run into the “those photos and videos are all fake, along with all the photos from space showing a round Earth” argument. Beyond the truly phenomenal logistical challenge of coordinating such a vast conspiracy, the feasibility of this argument collapses easily under this easy experiment that doesn’t require gaining access to the cockpit on a high-altitude flight:

Go to the beach. Preferably one near a busy harbor leading to the open ocean, and take a pair of binoculars. Bring sunscreen too – you may be there for a while. Find a large ship going out into the ocean (or just appearing on the horizon) and watch closely. You’ll notice that instead of just appearing or disappearing all at once (as would be expected on a flat Earth), at some point you will only be able to see the top of the ship before it disappears. This is because the horizon is curved, and the lower part of the ship will slip below the horizon before the top. Give it a try!

2) The Water Proof. If the Earth were round, rivers would have to flow uphill, and oceans would all move to the bottom of the globe.

This comes down to gravity. True flat Earthers don’t believe in gravity, because the flat Earth model is not compatible with our understanding of gravity – for numerous reasons that will become obvious as we go through each flat Earth proof. Gravity is a force that pulls objects with mass towards each other. The greater the objects mass, the stronger it’s gravitational pull. The Earth is big – it weighs around 5.9 septillion kilograms (that’s 24 zeros, it might interest you to know that we know this because of gravity – you can’t put the Earth on a scale). Because of this mass, it pulls smaller things towards it – you & I, buildings, cars, our atmosphere (gases have mass too!), the moon, and yes, water. Importantly, this gravitational pull is towards the center of the mass of an object – and so objects are pulled towards the center of the Earth. Since the earth is round, the gravity experienced by the water in rivers, lakes, and oceans is constant across the entire globe with two exceptions:

A) Inclines and declines created on the surface of the not completely smooth surface of the Earth. This is why rivers flow downhill – gravity!

B) Tides. In this case, the gravity from the Earth is uniform, but that rascally moon has sufficient gravity to give large bodies of water a pull too. The moon weighs 7.4 sextillion kg (22 zeros), which is 1/6th the size of the Earth, but it is over 230 million miles away, reducing it’s gravitational pull.

So what would happen if the Earth was flat? Water would be drawn towards the center of mass of the flat Earth – which would be somewhere towards the middle (depending on how uniformly thick the flat Earth would be). If you assume that gravity is real (try flying and tell me it’s not), then on a flat Earth, water would not always flow downhill – on the edges of the Earth it would flow towards the center. This is one of many reasons that gravity and flat Earth don’t mix.*

3) The Spinning Atmosphere Proof. If the Earth were round and spinning, things in the air would move in relation to the Earth. For instance, helicopters would just need to hover and wait for the Earth to spin underneath them to “move” or smoke would never move straight up – instead immediately appearing to move as the ground spins away. Also it would be impossible to make any progress by plane going against the rotation of the Earth.

We touched on the path to debunking this one in #2 above. The atmosphere has mass.  In total, it weighs about 4.9 quintillion kg (18 zeros). That’s a lot, but still much, much lighter than a similarly sized mass of liquids or solids. There is a very easy way to prove this by rapidly changing elevation in a car or a plane. At sea level, the mass of the atmosphere above you exerts 14.7 pounds per square inch (psi) on you. As you go up, there is less mass of atmosphere above you, and as a result less pressure. That reduction in pressure causes the air in your inner ear to expand as you go up, causing your ears to “pop”.

So when scientists say the Earth is spinning, they mean the whole Earth – including it’s atmosphere. The air above us is moving right along with us as the same speed – with the exception of wind currents which move relative to the surface of the Earth. So on a windless day, smoke will rise straight up until it hits the winds of the upper atmosphere. For their part, planes and helicopters will need to expend energy to move through the atmosphere, but they will not need to counter the rotation of the Earth, since the atmosphere they are flying through is moving the same way the Earth is. Make sense?

Here’s an easy way to show this works. Next time you are on a plane or a bus, sand up and jump. You’ll notice that you will land in the same spot that you took off from, despite the fact that you are traveling (in the case of a plane) at several hundred miles per hour. That’s because the air in your plane or bus is moving with you – it won’t push you back.

It is important to note that the rotation of the Earth does affect winds and ocean currents. This is another way we know the Earth is round. If the Earth wasn’t spinning, the atmosphere would circulate between the poles and the equator in a relatively straight line. However, because of the Earth’s rotation, atmospheric circulation (winds) and ocean currents are deflected, moving generally to the right north of the equator and to the left below the equator. This is called the Coriolis Effect, named after Gaspard Gustave de Coriolis, who died in 1843 knowing that the Earth was a sphere. In theory, the Coriolis Effect could cause the water in toilets in different hemispheres to drain in different directions. However, in practice, this is actually not true.

4) The Round Atmosphere Proof. If the earth is really a sphere, airplanes would fly off into space unless they adjusted their flight down.

This is a silly argument. Any pilot will tell you that maintaining level flight is not as simple as pointing the plane forward in a straight line and forgetting about it. There are down drafts, up drafts, turbulence, etc. Generally, a pilot maintains a level flight in one of two ways: by keeping the horizon in the same place relative to the nose of the plane, or by adjusting flight to keep a constant altitude according to an altitude gauge. Both methods will take into account the curvature of the Earth such that the plane will not go off into space. “Level” in the context of flight is literally defined by the curvature of the Earth.

In actual practice, it is impossible for planes to fly off into space anyway. First, since the atmosphere gets thinner as you get higher, the lift produced by the wings will eventually be too weak to keep the plane aloft – or at least to allow it to climb.  You can overcome this to some degree with very powerful engines, but there is also less oxygen in the upper atmosphere, and this makes the engines less efficient too. At some point, lift and thrust become limiting, and this defines the “ceiling” of a plane. Commercial airliners have a ceiling of about 45,000 feet – they can’t really go any higher. So you don’t have to worry about flying off into space the next time you fly out to see your friends in Las Vegas. You only have to worry about the hangover you’ll have on the way home.

5) The Lack of Motion Proof. If the Earth is spinning at 1000 miles per hour, how come I can’t feel it? Similar arguments are made about the movement of the solar system or universe through space. Also, why don’t we bounce around like in a car or plane?

We’ve covered that the atmosphere moves with the Earth, which is why it doesn’t feel like you are moving even though the Earth is spinning at 1000 miles an hour. The Earth doesn’t bounce around because it’s huge and traveling through the vacuum of space. Have you ever traveled on a large cruise ship or a really big plane (like an A380)?  These large boats and planes are way more stable and comfortable than smaller pleasure boats or commercial aircraft because of their size.  Well the Earth is about 1 quintillion times more massive than an A380.  A few gusts of solar wind aren’t going to cause it to bounce through space.

Click here for part 2 of UYBFS’s Flat Earth series.

Got a flat Earth proof you’d like debunked?  Add to the comments below.

* Interesting fact! Based on this same reasoning, on a flat Earth you would actually weigh less when standing on the edge of the Earth than you would when standing in the middle (wherever that would be).  This is because you would be farther from the center of the mass of the Earth out on the edge.  This would be easily testable with a sensitive scale.