Would cats push everything off a Flat Earth? A thought experiment rooted in real physics

Anyone who shares their home with a cat knows the fundamental rule of the feline universe: if it lies on the table, it must be pushed off. Whether it's glasses, pens, or phones, nothing is safe. This quirky behavior has earned cats media stardom and even placed them center stage in debates about the shape of the Earth. After all, who could resist the argument that if our planet were flat, cats would have already pushed everything off it? Yet if we take the subject seriously and apply real physics, we discover that gravity on a flat Earth would behave in ways that may surprise both sides.

Fig. 1. Artistic illustration of gravity on a flat Earth. Objects would not fall off the edge but would be pulled back to the planet, even when pushed off the rim.

When we try to imagine gravity on an alternative Flat Earth model, we often stumble because our intuition is shaped entirely by life on a spherical planet. Limited to a single experience, we inevitably draw analogies from what we know, not realizing how much our lives would change on a planet with a different shape. Having said that, altering the shape would not alter the fundamental laws of gravity. These laws would still apply, allowing us to build a physically consistent model of this highly speculative scenario.

What would remain unchanged?

When we watch a cat knock a mug off a table, it is tempting to imagine a flat Earth as if it were simply a giant tabletop. However, it is not the table that pulls the mug downward; it is the planet beneath it. Even on a flat Earth, objects would still fall to the ground, responding to the inward gravitational pull exerted by Earth’s mass. Gravity is always radial, meaning it pulls objects toward a planet’s center of mass (COM), as illustrated in Fig. 2. This remains true regardless of the planet’s shape.

Fig. 2. Radial gravity field of a spherical Earth.  Gravity vectors point toward Earth’s center of mass (COM), remaining perpendicular to the surface everywhere, which is why surface gravity feels uniform across the planet.

As a result, objects on a flat Earth would continue to fall toward the ground, even near the edges. Pushing an object off the rim would not make it “fall into space” any more than tossing it up makes it escape Earth's gravity in our environment. Gravity would constantly draw the object back, forcing it to follow an inward path toward the planet's surface. In both scenarios, to break free from Earth's gravitational hold, the object would need a propulsive force far greater than even the most determined feline can provide.

What would differ on a flat Earth?

On a flat Earth, cups, glasses, and pens would still fall toward the floor, bound by the planet's gravity. Earth would still have the same total mass, and that mass would still generate a radial gravitational field. What would change significantly is how mass is distributed around the planet's center of mass. And that is where things become interesting.

To visualize how gravity would behave on a flat Earth, imagine stretching the spherical planet into a flattened disk (Fig. 3). This transformation redistributes mass, decreasing its amount vertically and increasing it across a horizontal plane. As a result, those near the center of two bases would have less mass beneath, and therefore experience weaker gravity than those closer to the edge. As there is more mass distributed sideways, gravity at the edge would be stronger than in the middle, an outcome that often surprises both supporters and critics of a flat-Earth model.

Fig. 3. Gravity on a flat Earth. Gravity vectors point toward the planet’s center of mass, causing surface gravity to tilt inward everywhere except the central regions. As a result, most locations would feel sloped rather than flat.

Flat shape, different gravitational landscape

On a spherical planet, weight is constant everywhere because mass is uniformly distributed about its center. On a flat planet, we would be lighter at the center and heavier at the edge. The direction of gravity would also change, creating a new gravitational landscape beyond our imagination. The gravity would be perpendicular to the surface only at the center of both bases and along the midline of the lateral surface (Fig. 3). In those locations, we would feel fairly normal, albeit lighter than on the spherical Earth. Elsewhere, gravity would be skewed; the more so, the closer we get to the rim.

To adapt to the slanted gravity and avoid falling over, we would need to tilt. In our environment, tilting is required only on slopes, since gravity is otherwise perpendicular to the ground. On a Flat Earth, however, tilting would become a way of life, with the angle becoming steeper as we travel toward the edge. This would be a significant and unmistakable feature, constantly reminding us that we live on a flat planet. You can find more about this phenomenon in the post Gravity on a Flat Earth: living in a skewed wonderland.

Fig. 4. Gravity Orientation on a Flat Earth Disk. On a flat Earth, gravity would be perpendicular to the surface only near the center of the base and near the midpoint of the rim. Everywhere else, gravity would tilt inward toward the planet’s center of mass (located inside the disk), forcing people and objects to lean to remain balanced. As a result, in most regions, we would feel like standing on a continuous slope rather than on flat ground.

Due to the tilt, travelling from one edge to the other would feel like descending and ascending a slope. Starting from the edge, you would move along the gravitational vector (Fig. 3), which would assist your movement, making it feel like you were walking downhill. As you approach the center, it would seem like the slope levels out, and in the central part, it would feel like walking on flat terrain. Once you pass the central part, you move against the gravity vector. Consequently, this segment of your journey would feel like climbing uphill, with the slope growing steeper.

Comparing two incomparable worlds

Traveling across a flat Earth would feel like descending a slope and then climbing back up again. This would give us the impression of traveling along a concave curve (Fig. 5). Ironically, the more we flatten the Earth, the steeper this perceived curve would become. Flattening spreads mass farther from the center, therefore increasing the tilt experienced at the surface. This leads to a peculiar conclusion. The sensation of walking on a flat surface is only possible on a spherical planet. A flat Earth would destroy this sensation and create the illusion of moving over a curved terrain.  If Flat Earth proponents lived on a flat planet, they would probably claim it was curved.

In this strange setting, you'll find yourself caught between two conflicting signals. Visually, the land would appear flat, yet your body would insist otherwise. This sensation of a skewed landscape arises from the gravitational force acting on your body. Although the land's curvature is an illusion, the force itself is real. It's the same force that makes you lean forward or backward when ascending or descending hills in our own environment. This sensation is so strong that visual cues are unnecessary; you can feel a slope with your body. On a flat Earth, you would have this feeling on level ground

Fig. 5. Bowl analogy for surface gravity variation. The curved shape illustrates how gravity strength would vary across a flat Earth, with weaker gravity near the center and stronger gravity toward the edges.

The seeming curvature reflects the variation of surface gravity across the planetary disk. If we plotted surface gravity values along a cross-section, the resulting profile would resemble a bowl-shaped curve (Fig. 5). Traveling from one edge of a flat Earth to the other through the center would therefore feel like walking from one rim of a bowl to the opposite rim, passing through the bottom. Gravity would be strongest near the edges, decrease toward the middle, level out near the center, and then rise again symmetrically on the far side.

The bowl analogy provides a useful geometric approximation, but it has a problem. In our environment, if we were to walk inside a giant bowl, we would feel heavier at the bottom and lighter near the rim. This would be exactly the opposite of what would happen on a flat planet, where we would feel heavier and weigh more near the rim. Thus, in addition to sensing a gravitational slope, we would also experience continuous changes in weight as we traveled.

Fig. 6. Inverted arc analogy for gravity on a flat Earth. Walking inside this rainbow curve illustrates how gravity would be weakest at the center and strongest near the edges, while its inward tilt creates the sensation of moving along a curved gravitational path.

We could invert the bowl to correct the weight gradient, but walking upside down hardly helps the imagination. For a better mental image, we could stretch the inverted curve across the sky like a rainbow and imagine walking inside the rainbow curve from one end to the other (Fig. 6). This thought experiment would capture the full sensation of waking on a flat planet, with gravity being stronger at the rainbow ends and weaker at the center. Or we could just accept that this experience is beyond our imagination and trust in science. The laws of physics are consistent throughout the universe, allowing us to test any, even most brave hypotheses, successfully.