Over the past weekend, Saturn reached opposition in the sky—that is, it placed itself directly opposite the Sun, with Earth, in the middle, between the two. This also means that it’s at its closest to us. Even so, it’s more than 830 million miles away.
But what if a cosmic conspiracy pushed it out of its orbit and it took a strange turn and came knocking on Earth’s door? What if it came as near as the Moon? At that distance, it’d be disastrously close for a terrestrial or an orbital camera to take a photograph of it.
The sky would turn an unnameable hue, tinged with a shade of imminent menace. The horizon would be hijacked; the Sun, eclipsed. And there it’d be—a giant, slow-swirling ringed ball, standing four-square, occupying the entire field of vision.
That, of course, is theory. In reality, in the tug-of-war between the two worlds, ours would lose bitterly.
Because Saturn is nine times wider than Earth, and nearly 100 as massive, its immense gravitational force would begin to wreak havoc long ahead of its arrival. To begin with, it’d kick the Moon out of its orbit around Earth. Likewise, Earth’s gravity, though, far punier, would still act on it rings, disfiguring them.
But even if they were spared Earth’s token fury, they’d still not escape the Sun’s intense heat. As Saturn would head Sun-ward, the ice in them would sublimate—go from a solid to a gaseous state—creating a gigantic, trailing cloud of water vapor.
On the other hand, what would happen if Earth flew past Saturn? As one of its halves would be closer to Saturn than the other, Earth would be pulled more and more apart by Saturn’s mounting gravitational field.
When Saturn is at a distance 20 times greater than the Moon, its tidal forces would begin to come into play, exerting a pull equal to that of the Moon’s. That force would jump by a factor of 400, when Earth is about six million miles away. At this point, our oceans would be roiled, bringing biblical floods.
When Earth is at the same distance from Saturn as the Moon is from Earth—some 239,000 miles—fault lines would rupture, volcanoes would erupt, and anything left on the surface would be crushed.
At about 80,000 miles, Earth would collide with its rings. The tidal forces would then escalate to 200,000 times that of the Moon’s. As that proximity would fall well within Saturn’s Roche Limit (the distance at which a celestial body is ripped apart by the tidal forces exerted on it by another celestial body)—Earth would be ripped apart. And a new asteroid belt would be born as a result.