Thanks, AINZ. The popsci link continues to exclude me, but the ESRI original is excellent. This is the sort of planetary geometry game that I love to play - a "what if" scenario completely out of left field.

of course, slowing the Earth's spin would require the removal of a prodigious amount of energy, but we can pretend that some Sci-Fi device could do that - maybe transfer the spin to Venus or Mercury, or even our Moon (imagine if THAT visibly rotated?).

There would be further consequences of this out-of-equilibrium earth - the rocks would want to sag back to a sphere, too, but this would take a long time. Glacial rebound in the Baltic sea region is moving at the rate of about 1 cm per century, and a 10,000 to 100,000 year timescale should see most of the load relieved, but I rather suspect that a wholly out-of-figure Earth with 8 km of long-wavelength topographic mkissfit would triger planet-scale earthquakes like those that formed the thrust sheets on the crust of Mercury, except they would all be happening in a hurry! The article does mention these effects, but moves on quickly.

An interesting thought experiment...