What If the Earth Suddenly Turned Flat?

By Ryan F. Mandelbaum on at

The Earth is a round orb, almost four thousand miles in radius, orbiting a star alongside some other orbs of varying sizes. We’ve taken pictures of it. But some folks don’t believe any evidence presented to them by a government agency. Many have come to the conclusion that the Earth is actually flat.

What does flat mean? The models I’ve seen posit that the Earth is a disk with the North Pole in the centre, bounded by Antarctica at the edges.

We wanted to know what would happen if the Earth really did become flat. In this instalment of Giz Asks, we asked weather and climate researchers, seismologists, astronomers and physicists to consider our planet suddenly turning to a pancake. The answer is, pretty universally, certain death.

Susan Hough

Seismologist at the United States Geological Survey and Author

If the earth were to suddenly flatten, presumably all sorts of hell would break loose. I guess it would depend on how flat is flat. If we’re talking pancake flat, gravity would be an immediate problem: gravitational attraction goes as G(m1*m2)/r^2, where G is the gravitational constant, m1 & m2 are two masses, and r is distance. A sphere is the 3D shape that maximises surface area relative to volume, which kind of gives gravity the biggest bang for its buck. If you flatten the sphere, the far side gets closer to the new centre point, but the ends spread way out, so surface gravity goes down at the centre, and way down at the edges. Lose gravity and bye-bye atmosphere.

Other first-order problems: heat, radioactivity, etc. In our spherical earth, both of these are concentrated in the core. If the earth were flattened, they would have to go somewhere—presumably a lot closer to the surface.

Marek Kukula

Public Astronomer at the Royal Observatory in London

The Earth is round because its own gravity inevitably pulls it into a spherical shape. To somehow make it go flat and stay flat, you’d first have to find a way to switch off the effects of gravity. This would have the unfortunate side effect of allowing the Earth’s atmosphere to float away into space, rapidly followed by anything else not physically attached to the surface. So, unfortunately, there’d be no weather and no life.

Carol Finn

Research Geophysicist at the U. S. Geological Survey, and Past President of the American Geophysical Union

Here are some thoughts. I made several assumptions—one is that the Earth would be flattened like the Flat Earth people think about it—that is all continents and oceans are on the same side (as opposed to the northern hemisphere on one side and the southern hemisphere on the other—although many of the things that I talk about below would operate in both cases). I also assume that the Earth is rotating on its axis, that is spinning like a Frisbee, and still revolving around the sun which is still 93 million miles away:

1) Gravity: in the centre of the flattened Earth, it probably would feel similar to now. At the edges, the gravity field would start to point slightly toward the centre, making it increasingly difficult to move toward the edge. It might feel like you are going up an increasingly steep hill. Once you hit the edge, you could walk more easily on the side of the Earth disk, as you’d be pulled toward the centre of the Earth again (might feel like now). If there was a bottom side (occupied by the 80% water and parts of South America and Africa, as well as Australia, New Zealand, etc.) you’d be pulled toward the centre (walking down a steep slope) once you got off the side of the disk. Because of the large mass of even a flat disk, I doubt someone would fall off the edge into space. I don’t know what the Flat Earthers think lies under the Flat Earth disk, if all of the current Earth were on one side.

2) Everyone would see the same stars over a 24 hour period.

3) On clear days, you would see forever—you wouldn’t for example, see the bottom of a boat disappear before its top from the horizon as it does now because of Earth’s curvature because there would be no curvature.

4) If Earth were totally flattened, there would be no plate tectonics as we know it today, because that requires large (1000s of km) of convection cells in the mantle, so I imagine those would stop moving. So that means that it is unlikely that new mountains like the Rockies would be formed nor would deep trenches in the ocean. But even without mantle convection generating heat, the core radioactive heat sources would be close to the surface so could make it very hot with possibilities for lots of volcanism until the radioactive core stopped generating heat. This would be like current day Mars and Venus. The oceans might boil away. We’d probably be dead.

5) Depending on the thickness of Earth there probably would not be a magnetic field because it requires two poles and a flat disk would only allow one pole. Without the magnetic field the solar wind would strip away the ozone layer that protects us from harmful ultraviolet radiation and we’d be dead.

6) Lots of volcanism would cool the climate. All air currents like the jet stream and ocean currents like the Gulf Stream would change which would drastically change the weather. I just don’t know how—better to ask a meteorologist or person studying climate, ocean currents, etc.

Jeff Masters

Director of Meteorology at Weather Underground

Let’s assume the Earth is flat like on the UN logo, with all the continents surrounding the North Pole, bounded by oceans. To keep the oceans contained, the edge of this flat Earth has a huge wall (with lots of advertising billboards and a considerable area of solar panels.) We might as well have the Sun orbit this flat Earth. The weather would be pretty boring (but much safer!) on this flat Earth, since there would be no seasons. Seasons come about because of the tilt of the spherical Earth’s axis, and a flat Earth would see no change in incoming sunlight at different times of year. Furthermore, the flat Earth would not have a North Pole and South Pole with cold weather and an equator with hot weather, since the sun would shine down with uniform intensity over the entire flat Earth. Temperatures world-wide would be about the same, though the land areas would be warmer during the day than oceans, and cooler at night. There would be no snow except at high elevations in mountains.

The only physical process to drive weather, then, would be land breezes, sea breezes, and topographically-induced winds. With the Earth no longer rotating, there would be no spinning motion to drive storm systems, and thus no hurricanes or large rain-bearing low pressure systems would form. In order to get rain, one needs a mechanism to get air rising so that the moisture in it cools and condenses. Thus, the only rain would occur in the afternoon, when solar heating of land areas would create a sea breeze which would move inland, forcing air to rise along the edge of the breeze, creating gentle showers or the occasional mild thunderstorm. Heavier thunderstorms might occur in mountains where the sea breeze hits some topography, forcing the air to rise more violently upwards. Severe thunderstorms with hail or tornadoes would be extremely rare. Since the sea breeze would likely only penetrate a few tens of kilometres inland, due to the relatively low contrast in temperature between the oceans and land areas, the interior regions of all the continents would be vast deserts where rain never falls. It would never rain at night anywhere over land, though some weak nighttime showers might develop over the ocean areas, due to land breezes that would blow out over the ocean at night. The best analogue in today’s world to the weather of the flat Earth would be Saudi Arabia’s weather. I predict employment of meteorologists would be very low.

Anders Sandberg

Futurist, Future of Humanity Institute at Oxford University

So, let us assume that Earth for some reason (a wizard did it?) unpeels and turns flat. Let us also assume that we can ignore the first order effects of accelerating enormous masses at huge speeds (which are likely to produce enough heat to melt the whole thing). Instead, we now have a layer cake with the Earth’s crust on top of a cylinder of mantle on top of a cylinder of core. The thickness under the flat top is a third of the original radius, 2123 km. (Why? Volume 4piR^3/3 divided by area 4piR^2 = R/3.)

Problem 1: If you flatten a sphere by peeling it like an orange skin you get titanic rifts and edges. This is a bit like Jack van Wijk’s myriahedral map projection.

Problem 2: Gravity. If we assume the world is now roughly cylinder-shaped the gravitational acceleration at the centre will be weaker than on Earth—there is less stuff below your feet to pull you down, so gravity will be about 30%! (Assuming I calculated right based on 5.4.7.) However, near the edge of the flat Earth gravity will be weaker and point downwards towards the centre - it will be slanted relative to the surface.

This spells trouble: essentially the edge regions are like immensely high mountains, and the air will rush down toward the centre of the flat surface. Crazy storms and suffocation will ensue. A bit more slowly the oceans will be arriving. And after that, the rocks. There is a maximum height for mountains in a given gravity set by the strength of rocks. On Earth it is about 10 km. Even if we divide by the weaker gravity the “mountains” of the edge will be thousands of kilometres too tall.

Roughly the same problem happens near the giant rifts, with the added entertainment that on one side of the “mountain” you have normal landscape, on the other side millions of square kilometres of really hot lava. Which is currently and instantly releasing all the stored volcanic gases in the ultimate pyroclastic eruption. The Siberian Traps flood basalts (suspected of causing the end-Permian mass extinction) would look like a flickering candle next to this.

If we assume we just have a flat disk with no rifts, and the wizard keeping it disk-like through magic rather than allow it to collapse into a molten ball of lava, gravity will produce a central ocean. This will be roughly a hemisphere of radius 863 km, far deeper than any current ocean (a bit like the ones imagined on exoplanet waterworlds with high pressure ices at the bottom) covered by a normalish atmosphere, a ring-shaped beach zone where maybe life could continue, and barren rocky uplands with no air.

Living around the ocean might not be too weird. Sure, there is a sloping mountain stretching forever and the ocean gets super-deep, but other than that it would look like many places on Earth. Of course, this assumes Earth’s rotation remains reasonable...

Were the rotation axis to go through the centre of the disk you would have a half-year summer of 24 hour sunlight followed by half a year of no sunlight—the temperature swings would be fierce. If the axis is instead such that you get normal days I think the temperatures would be pretty normal. Since the ocean would be closer to the rotation axis than most of the surface of our current earth, the Coriolis forces that drive cyclones would be weaker: the weather would be more convection-driven rather than driven by big cyclones and fronts. Probably no big hurricanes, which might always be something.

In short, a flat Earth would—if it did not turn into an apocalyptic implosion straight away—be a smaller, calmer world with lighter gravity. But make sure the wizard keeps things in shape.

Janine Krippner

Volcanology and Remote Sensing PhD Candidate Department of Geology and Environmental Science University of Pittsburgh

What an interesting question! One I haven’t thought of before beyond the meme that if the Earth were flat, cats would have knocked everything off by now. So here are my thoughts.

As a volcanologist, the first question that comes to mind is how would we have magma for volcanoes? I guess a flat earth would be a slab? This would mean that we wouldn’t have our sphere with increasing pressures and temperatures with depth that melts rock. Plate tectonics are the planet’s way of recycling material. Very simply—plate goes down under another plate, releases water, water rises and reduces the melting temperature of the rock, rock melts in tiny bits, tiny bits of melt rise (because they are less dense than the surrounding rock), this eventually forms a magma reservoir, which can rise and pressurise—leading to an eruption. The majority of volcanoes are produced at these tectonic boundaries, either where they move apart, or one subducts under the other. I can’t imagine how this would continue without the Earth being a sphere. So if plate tectonics stopped, and we eventually stopped having volcanoes, we lose all the precious resources that come with them—they contribute to very fertile soils around the world for one major example. If a flat Earth did manage to obtain an atmosphere, I wonder what would happen when we lose volcanoes—that have been contributing to our atmosphere (including a lot of water!) since the beginning of time on Earth.

Over millions of years, mountains would erode—there are no plate tectonics to keep them growing upwards. Think the Appalachian mountains in the eastern US—they used to be a large mountain chain which eroded, and all that material filled in a large depression which now includes states such as Pennsylvania. That is a huge amount of eroding material that has to go somewhere so lower areas around them would flatten out. Not to forget how much it would suck for there to be no more gorgeous mountains, or to have no more snowboarding and skiing, but those mountains store a lot of water in snow that feeds rivers and provides drinking water for people to live. Everything would eventually get very flat—think Illinois. I haven’t been there, but the mention of it brings people to complain about how boring it is to drive through because it is so flat. So everyone that lives on a mountain, or in a lower area around a mountain, is going to have to adapt to their home disappearing or being buried (if we can imagine that people lived to see that).

So beyond the concerns of how would we maintain a magnetic field without a moving core, how would we survive radiation without a magnetic field, and would our water just fall into space? I struggle to think how we would maintain volcanism, a global process that has occurring throughout Earth’s history. Plus, I guess I would be out of a job and that would be pretty devastating.

Dave Stevenson

Professor of planetary science at the California Institute of Technology

It’s a rather ridiculous question. I’ll give you an answer that is, if you will, a physics answer. Imagine if you took the Earth as it is now and changed it into a flat pancake or a hockey puck. Then what would happen is that because of gravity, it would want to go back to being a sphere. It would do so catastrophically. The amount of energy released would be similar to what you would get if you made the entire Earth out of high explosive such as TNT. It would literally collapse upon itself and break. There’s no material strong enough to hold it up. It would collapse from something shaped like a hockey puck to something shaped like a sphere. It would do so on a timescale of an hour.

You would die for sure.

Leila Ertolahti

A adjunct professor in geology at Fairleigh Dickinson University

I’m guessing we’re just ignoring air/space travel, how unusual it would be for our planet to be flat when all the other objects in the sky are round, and the fact that Earth would collapse back down immediately, if we suddenly flattened it and the same laws of physics still apply...

Assuming it doesn’t collapse back down, but stays flat, we would additionally need to assume that the magnetic field magically is maintained. The magnetic field is generated by something called the dynamo—essentially the movement of molten metal in the outer core, around the inner core of solid metal. Without the current structure of the Earth and this motion the magnetic field would collapse, and we would end up much like Mars. The solar wind would quickly strip us of most of our atmosphere and life (as we know it) would perish.

If we somehow artificially managed to create an atmosphere (one that also can protect us from UV radiation, in addition to allowing us to breathe, or we’ll all get cancer), no magnetic field would still wreak havoc in terms of navigation for both people and animals, we wouldn’t have the northern or southern lights (auroras) anymore. The loss of the dynamo means no plate tectonics—which means no more volcanoes, no more earthquakes, no more plates moving around on the surface of the Earth.

If none of those mattered...

I originally assumed that the Earth would be flat, and horizontal (since that seems to be a popular depiction and that people/water could just fall off the edge if one went far enough). Looking at the sky, no matter where you went the stars would be the same. You wouldn’t have different stars on one half of the disk as you would on the other. The moon would have a straight, not curved shadow (since it’s Earth’s shadow). If it’s a horizontal disk there is no more night and day. Also in this case changes in relief (elevation) would not change your field of view (eg. being on top of a mountain wouldn’t offer a further view than standing on a flat prairie would).

What about if we made the Earth entirely vertical? (And everything magically stays on the disk, even though it’s sideways). We would have night and day then though everywhere would have the same length of day. The sun would always travel overhead, so “land of the midnight sun” would no longer exist. Climate would be the same everywhere. We wouldn’t have wind belts etc.

Tanya Harrison

Director of Research at the Arizona State University NewSpace Initiative

If the Earth were to suddenly become flat, all the stuff that’s currently inside the spherical Earth would have to go somewhere. That means the radius of the flat Earth would have to increase to accommodate the displacement of the interior layers. Or, the flattening surface would experience a hellfire of volcanic activity as the mantle became increasingly compressed. (Cool side note: This is why Jupiter’s moon Io is so volcanically active: It’s being squished and squeezed by tidal forces from Jupiter.)

A change in the Earth’s radius would create chaos on the ground as it messes up the orbits of satellites, critical for everything from communications to navigation to timekeeping in today’s society.

In the answer below, I am assuming the Earth is still rotating on an axis orbiting around the Sun.)

Flattening would affect climate and weather as it would increase or decrease the amount of direct sunlight a particular location receives, depending on if the flattening occurred along the polar vs. equatorial axis. If the Earth flattened along the equatorial axis, global temperatures would decrease. The flat surface of the Earth perpendicular to the Sun would experience perpetual twilight, with the Sun never raising much above the horizon. If the flattening occurred along the polar axis—that is, the Earth essentially became a disk facing the sun—temperatures would increase. The transition from day to night would be quite abrupt, without lingering sunsets to enjoy.


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