Sail On, My Little Honeybee

There is an altitude above every planet where a moon can orbit forevermore. In millions of miles of ups and downs, there is one narrow passageway of permanence. If a moon can reach this groove, it will never crash down like masonry nor drift away like a mood; it will be inalienable; it will circle its planet at the exact speed that the planet rotates, always over one site, like the badlands or Brazzaville or the Great Red Spot, so that the planet neither drags the moon faster nor slows it down. Moons not locked into this synchronous orbit are either being perturbed up or down.

The law is stringent about this; there are no clauses; and all moons are dutiful followers of the law. But, as all good followers of the law discover in the end, unless you happen to roll onto a track precisely determined by your mass and your planet’s mass, the law ejects you or dashes you down. One moon in our solar system has achieved synchronous orbit, being pledged forever to its planet--Pluto’s moon Charon. The other 168 moons have not.

Mars has two small moons whose names mean “panic” and “terror.” Phobos looks like a potato that experienced one terrible, and many average, concussions. Phobos hurtles around Mars every eight hours, which is three times faster than Mars rotates, which means Mars pulls it back and slows it down. Slowing down makes a moon lose height; in the end Phobos will smite its planet, or else get wrenched apart by gravity into a dusty ring of aftermath. Mars’s other moon Deimos is a slow and outer moon--an outer and outer moon--someday it will be a scrap moon, rattling around in the outer darkness, where drift superannuated spacecraft and exhausted starlets.

So fast moons slow down and slow moons speed up, and only during excerpts of time do planetary dalliances appear permanent. Our moon through many excerpts--the Moon--is a slow moon. Thus it is speeding up, thus it is falling up, coming off like a wheel, at one and a half inches per year. Let us now reflect upon the Moon; for the Moon has long reflected upon us.

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