If the Earth Stood Still

July 12, 2010


The following is not a futuristic scenario. It is not science fiction. It is a demonstration of the capabilities of GIS to model the results of an extremely unlikely, yet intellectually fascinating query: What would happen if the earth stopped spinning over a period of a few decades? ArcGIS was used to perform complex raster analysis and volumetric computations and generate maps that visualize these results.

If earth ceased rotating about its axis but continued revolving around the sun and its axis of rotation maintained the same inclination, the length of a year would remain the same, but a day would last as long as a year. In this fictitious scenario, the sequential disappearance of centrifugal force would cause a catastrophic change in climate and disastrous geologic adjustments (expressed as devastating earthquakes) to the transforming equipotential gravitational state.

The lack of the centrifugal effect would result in the gravity of the earth being the only significant force controlling the extent of the oceans. Prominent celestial bodies such as the moon and sun would also play a role, but because of their distance from the earth, their impact on the extent of global oceans would be negligible.

If the earth’s gravity alone was responsible for creating a new geography, the huge bulge of oceanic water-which is now about 8 km high at the equator-would migrate to where a stationary earth’s gravity would be the strongest. This bulge is attributed to the centrifugal effect of earth’s spinning with a linear speed of 1,667 km/hour at the equator. The existing equatorial water bulge also inflates the ellipsoidal shape of the globe itself.

If the earth stood still, the oceans would gradually migrate toward the poles and cause land in the equatorial region to emerge. This would eventually result in a huge equatorial megacontinent and two large polar oceans. The line that delineates the areas that hydrologically contribute to one or the other ocean would follow the equator if the earth was a perfect ellipsoid. However, due to the significant relief of both the continents and the ocean floor, the hypothetical global divide between the areas that hydrologically contribute to one or another ocean deviates from the equator significantly.

Analogous to the well-known U.S. Continental Divide, this would be the border separating two giant hemispherical watersheds of the new circumpolar oceans.

That’s from the folks at the ESRI.

Interestingly, the earth will eventually stop spinning due to negative tidal acceleration. The moon’s tidal forces on the Earth’s oceans have since the moon’s inception cause days to be about 2 hours longer than they were about 620 million years ago. At that time, there were about 400 days in a year. However, the time when the earth will eventually stop spinning will never come. Due to the Sun’s increase of radiation, the earth’s ocean (there’s only one ocean since they are all connected) will be completely vaporize in about 2.1 billion years from now which will remove the bulk of the mass that causes tidal friction.

Again, due to recent calculations, a time when a day is a month long will also never come because the sun will by then evolve into a red giant and destroy both the Earth and the Moon. Cool stuff.