No, no, no. Your fiancee has got it all wrong. Let me explain IO's madness. It all has to do with the Moon (It is full right now isn't it? Go ahead look outside!) Let me just take a minute here to explain the phenomenon very clearly in laymen's terms.
You see, the Moon moves around the Earth in an elliptical orbit of small eccentricity, inclined by 5 deg 8' 43''.4 to the plane in which the Earth revolves around the Sun. Its distance from the Earth varies between 356,000 and 407,000 km (221,000 and 253,000 mi) in the course of each month; the average distance is 384,400 km (238,900 mi), less than 1% of the distance to Venus and Mars, even at the time of their closest approach. The lunar globe appears in the sky as a disc of a little over half a degree (31' 5''.2) in apparent diameter.
The period in which the Moon completes an orbit around the Earth and returns to the same position in the sky--the sidereal month--is 27 days, 7 h, 43 min, and 11.6 sec. Because the Earth is moving in its orbit around the Sun in the same direction as the Moon, the time needed to return to the same phase--the synodic month--is longer: 29 days, 12 h, 44 min, and 2.8 sec. This period is the time interval that, for example, elapses between two successive full moons, a period that was known within a second even in ancient times. The Moon's average velocity is 1.023 km/sec (0.635 mi/sec), corresponding to a mean angular velocity in the sky of about 33 minutes of arc per hour, a little greater than the apparent diameter of the Moon.
In addition to its motion through space, the Moon also rotates about its axis in a period of one sidereal month, so that it keeps approximately the same side toward the Earth at all times. Nonuniformities in its orbital motion, however, together with the inclination of the orbit to the ecliptic, cause "optical librations" that allow 59% of the entire lunar surface to be seen from the Earth at one time or another. The remaining 41% was hidden until the Soviet LUNA 3 spacecraft photographed the far side in October 1959.
I hope you now see how obvious it is that IO is behaving the way it is.
If anybody wants to talk about IO's fundamentals, I don't want to hear it! Ignorance is bliss!
BTW, I'm sure glad I held on to my stocks that I loaded up on in the teens. I was tempted to sell, but I think this still has some (no, a lot of) gas left in it. |
