Back in 1978, moviegoers were treated to an amazing sight: Superman reversing the spin of the Earth, turning back time in the process (and saving his beloved Lois). Preposterous, of course, but what if something did change the Earth's rotation? What if the rotation stopped completely?
Let's get our admittedly far-fetched assumptions on the table. First, let's assume the Earth stopped spinning gradually, as a sudden deceleration would mean disaster. Second, we'll suppose that Earth's ecosystems have survived the transition mostly intact. So what does this new world look like?
For starters, Earth would now take a whole year to do what it pulls off in a day: cycle from night to day and back. Cities would spend half the year in darkness and half the year in full sunlight, just like the North and South Poles do today. And, like the poles, every region would still experience different seasons, but the temperature swings from season to season would be much greater for areas along the equator. An equatorial region would spend infernally hot months very close to the sun, while that area's global counterpart would spend dark, frigid months very far away from it. That's trouble for the plants and animals that have adapted to the climate of a region and, consequently, for the people living there as well.
What's that? You're relocating to the relatively stable (though still awfully cold) polar regions? Bad move. They're deep underwater. In fact, the boundaries between ocean and land on a spin-free Earth would look nothing like they do today. Because the Earth rotates, centrifugal force causes the planet to bulge along the equator. No rotation, no bulge. Without that bulge, all of the extra water held in place along the equator would go rushing back toward the poles. Esri, a company that develops geography-focused technology, modeled the world's land and oceans after its equatorial bulge subsided and found that the Earth would have a band of land -- one giant supercontinent -- that circles the equator and separates two massive oceans to the north and the south.
As if that weren't enough, Earth's magnetic field might go away, too. While we're not entirely sure how that magnetic field is generated, one leading theory states that it's the result of Earth's inner core rotating slightly faster than outer core (yep, two different rotations on one planet). If both of them stop, the mechanism behind Earth's magnetic field may as well, leaving us exposed to potential harmful solar winds [source: Cain].
Where does that leave us? Humans are an adapatable species with powerful technology at their disposal, but survival in this new environment would be a challenge. Sure, we could try to light our homes in the darkness and heat and cool them (at great cost) during wild temperature swings, but not everything would be under our control. Could crops survive the extremes of this new world? Could any plants? If not, the entire food chain would be in danger. Perhaps we could find new crops or modify existing ones to tolerate this new environment. Or maybe we would become dependent on perennials that return with warm weather. It's actually a little comforting to think that, while the world will probably become a hellish place to live, at least our decorative hosta beds might be OK.