Quoth Harold Groot on rec.music.filk:
Actually, it's not a PERFECT lock. I understand that you do get just
a bit of wobble back and forth (the orbit isn't a perfect circle,
etc.). If the Earth is right on the horizon, the (libration?) would
make it rise and fall just a tad. I don't know if it would be enough
to cover the entire diameter of the Earth.
Is this the Terra that we gazed on?
Is this the planet that we knew?
I don't remember seeing it vary...
When did you?
When did we undergo libration
When did the earth begin to move?
Hasn't it locked us in a cosmic groove?
Earthrise, earthset
Earthrise, earthset
Every day the same
Unchanging, there on the horizon
Bordered in atmosphere and flame
Earthrise, earthset
Earthrise, earthset
Gently flow the weeks
Barely perceptible nutation
Tracing its undistinguished peaks
How did we get to have a wobble?
Why do we move from side to side?
Shouldn't the motion have been braked
By tides?
Isn't it time the world was stable?
What good's an orbit if it veers?
Why must we wait another billion years?
Earthrise, earthset
Earthrise, earthset
Still it carries on
Hanging there over the horizon
Flooding the shadowlands with dawn
Earthrise, earthset
Earthrise, earthset
Gently flow the years
Harmonies superposed on cycles
Thrill to the music of the spheres