Carpe diem—seize the day; everything passes quickly away.
We see Saturn’s rings as an abiding feature of the solar system. But if we are to believe “Observations of the chemical and thermal response of ‘ring rain’ on Saturn’s ionosphere,” the rings are transitory. In a mere three hundred million years, less time than has elapsed since the Permian Extinction, the rings may be reduced to wispy remnants of their former glory, like the frail rings we see around Jupiter, Neptune, and other outer planets.
Nor are Saturn’s rings the only marvel slated to vanish in the near future. Mars’ moon Phobos is spiraling inwards toward the planet; it will either form a ring system or impact the surface of Mars. This may happen in fifty million years or so, less time than has elapsed since the more enjoyable Paleocene–Eocene Thermal Maximum.
Consider Earth’s Moon. It is slowly migrating away from the Earth. At present, the Moon’s apparent diameter is almost exactly the same as that of the Sun. When the two line up, we get to enjoy total eclipses of the sun. But as the Moon recedes, its apparent diameter will diminish and there will be no more total eclipses. Just transits of the Moon. How sad! At the Moon’s current rate of retreat, this may happen in a mere six hundred million years, which is barely enough time for a couple of supercontinents to congeal and then swirl apart.
And Mercury’s orbital eccentricity is apparently increasing. In just a billion years, it may swing out to collide with Venus, which would be bad. It could even collide with Earth (which would be worse). But we would probably have killed ourselves off by then, so it’s all cool. Except perhaps for the cockroaches that have inherited the Earth.
Neptune’s moon Triton may be a captured Kuiper Belt Object (like Pluto). If so, its arrival trashed the moons already orbiting Neptune, scattering some and absorbing others. Now it is the largest body orbiting Neptune; it’s way more massive than all the other moonlets added together. It has a highly inclined, retrograde orbit. It will be drawn toward Neptune until it is torn apart by tidal forces … in four billion years or so. That’s just about the time that the Andromeda Galaxy and the Milky Way will be busy with their long-anticipated merger.
So don’t delay seeking out the chance to marvel at Saturn’s rings, total eclipses of the sun, or other wonders of the cosmos. All are temporary—and even if that’s on a scale that seems unimaginably long to you, you’re an even more transient event in a civilization that may eventually be a smudge between two adjacent sedimentary layers. Never send to know for whom the bell tolls; it tolls for thee.
In the words of Wikipedia editor TexasAndroid, prolific book reviewer and perennial Darwin Award nominee James Davis Nicoll is of “questionable notability.” His work has appeared in Publishers Weekly and Romantic Times as well as on his own websites, James Nicoll Reviews and Young People Read Old SFF (where he is assisted by editor Karen Lofstrom and web person Adrienne L. Travis). He is surprisingly flammable.