The Earth’s familiar spherical shape is a direct consequence of gravity, which pulls all mass toward a common center. For any celestial body exceeding a few hundred kilometers in diameter, self-gravity overcomes the material strength of rock, forcing the object into a shape that minimizes gravitational potential energy—a sphere. This thought experiment explores a hypothetical world where Earth’s mass is fixed in a perfect cube, ignoring the instability that would instantly cause it to collapse. Analyzing a cubic planet allows us to understand the fundamental consequences of gravitational physics on a non-spherical body. The forces governing the distribution of water, air, and the experience of walking would be profoundly different.
The Non-Uniform Pull of Gravity
Gravity on a spherical planet acts uniformly, always pointing toward the center of mass. A cube, however, would present extreme variations in gravitational force across its six faces, twelve edges, and eight corners. Gravity would be at its maximum magnitude at the exact center of each face, where the surface is closest to the planet’s center of mass.
Conversely, the eight corners would be the farthest points, causing the magnitude of gravity to drop significantly—potentially to less than 65% of the face-center value. This difference in distance creates a corresponding difference in gravitational pull. The most important effect, however, would be the direction of the gravitational vector.
As a person walks away from the center of a face toward an edge, the gravitational pull would deviate from the perpendicular, no longer pointing straight “down” relative to the surface. The force vector would point toward the cube’s geometric center, creating a growing horizontal component of gravity. This means the flat face would feel like a constantly increasing incline, forcing one to walk perpetually uphill toward the edges. Near an edge, gravity would point at a significant angle to the surface, making standing upright a balancing act against a massive sideways pull.
Where Would the Oceans Gather?
The behavior of liquid water on a cubic planet is determined by the gravitational equipotential surfaces, where gravity exerts no tangential force. Liquid water cannot sustain shear forces, so it would flow away from areas of higher gravitational potential energy and pool into the six gravitational “wells” located at the center of each face.
This flow would evacuate all water from the edges and corners, forming six vast, circular oceans centered on the face planes. The cubic edges would become massive, dry, high-altitude ridges separating these six seas, effectively acting as the new global “sea level.” The surface of the water would not be flat, but would form a lens-like shape, following the subtle spherical curve of the equipotential surface within the well.
The eight corners would be desolate, arid peaks towering above the six ocean basins. Precipitation falling on the elevated edges would immediately flow down the steep gravitational gradient toward the center of the nearest face. This creates a world separated into six isolated hydrospheres, with no liquid connection between them across the immense, dry barriers.
Atmospheric Dynamics and Climate
The atmosphere would respond to the non-uniform gravity in a manner similar to the oceans. Air pressure, which is a measure of the weight of the air column, is determined by gravity. Consequently, the atmosphere would pool thickly over the six face centers, creating areas of extremely high pressure and dense air.
Conversely, the edges and corners, being the furthest points from the center of mass, would experience the weakest gravitational pull and have a dramatically thinned atmosphere. At the eight corners, the gravitational force could be so diminished that the atmosphere might leak into space over geological time. The immense difference in atmospheric density would drive chaotic, powerful wind patterns.
Air would constantly flow from the high-pressure face centers toward the low-pressure corners and edges, creating extreme weather systems and perpetual high-altitude winds. The planet’s rotation would twist these air currents, complicating global circulation and distributing heat unevenly. Climate zones would be dictated by proximity to the six gravitational wells, with face centers having temperate, dense atmospheres and the edges suffering from low pressure and exposure.
Geography, Structure, and Habitability
The geography of a cubic world would be defined by stark extremes and the bizarre gravitational field. The six faces would feature immense, relatively flat ocean basins, transitioning abruptly into the massive, high-altitude ridges that form the cube’s edges. The eight corners would stand as towering, uninhabitable peaks under a near-vacuum.
Building any permanent structure outside the center of the faces would be a major engineering challenge due to the significant sideways component of gravity. Near the edges, a building would need to resist not only the downward pull, but also a constant, massive force trying to slide it toward the nearest face center. Over geological timescales, the immense weight of the edges and corners, combined with the uneven gravitational stress, would likely cause the planet’s material to deform and collapse.
Habitability would be restricted almost entirely to the six low-altitude, high-pressure, dense-atmosphere regions at the center of the faces where life could be sustained. Any attempt to venture toward the edges would be met with the sensation of climbing a steep, invisible slope, culminating in an environment with dangerously low atmospheric pressure and a gravitational pull too weak to feel secure. Life would be confined to six distinct, isolated biospheres separated by impassable, arid, high-gravity-gradient mountain ranges.