The Seventh House

When the Moon is in the seventh house

And Jupiter aligns with Mars

Then peace will guide the planets

And love will steer the stars.

   James Rado, Gerome Ragni

   In “The Age of Aquarius”

Among the constellations of the zodiac, the seventh house is Libra, the scales. Those born between September 24 and October 23 are born in Libra, but (and don’t be surprised) the sun doesn’t rise in Libra at that time of year. Astrology is, as it were, behind the times. The actual, you might say physical, period of Libra’s rule arrives on November 6 and lasts until November 20. There was a time, of course, when the sun, rising at dawn—and not yet shining brightly enough to obscure the sky immediately above it—would be rising in the seventh house. But that was a long, long time ago. The culprit here? It is the precession of the equinoxes.

Now that’s a subject for the geometrically challenged (turns out) and also for the linguistically lazy. Precession? Well it means “coming before.” But what is it that “comes before”? Well the phrase tells us. The equinoxes come before. But before what? It drives you crazy all this techno-jargon. The answer is that every year, the equinoxes arrive 20 minutes before they…ought to—that is to say if we measure time not by our experience of the sun, thus locally, but in reference to the stars. Junk yard dog that I am, today I discovered that there is a so-called sidereal year and also a tropical year. The first comes from the Latin sidereus, “starry,” the second from tropicus, “related to a turning,” thus of the seasons. The first of these is the time it takes for the sun, as seen from the earth, to be in the same place against the fixed stars, thus in the House of Libra, for example. That time is 365.25636 days. Remember. We’re measuring by the stars. The tropical year is the time it takes the equinoxes to return; days and nights are of equal length.  That year takes 365.2421988 days. The difference here is 20.4 minutes. Thus the end of the year, as measured by seasons, comes 20.4 minutes before it should, looking at the fixed stars.

But this, of course, presents a logical problem. What causes this 20 minute difference? The answer is that the earth has two different kinds of rotation. The whole of the earth rotates around its axis—once every twenty-four hours. But the axis itself also rotates—describing a circle, if viewed against the fixed stars, every 25,920 years. It’s movement is tiny—but it results in a slight change in the seasons if their beginning is measured against the fixed stars. Therefore Polaris is only our North Star temporarily—and by 4100 it will point at the Constellation Cepheus, where that constellation’s bright Alderamin will have become the “pole star.” To explain the “wobble” of the axis most people refer to the behavior of gyroscopes or to the wobble of a spinning top. Those examples illustrate axial wobble—but in our case the time scale is so great, speaking of a wobble suggests more motion than is perceivable. We’ve known about this wobble, however, since the Greek astronomer Hipparchus (circa 190-120 BC) discovered it.

There is, therefore, no logical problem. The fixed stars are a great clock—and measure time unerringly. But in their case it really matters from where you’re looking as you are consulting the clock. That wobble moves us ever so little every year, hence we must correct for that movement every time. When we do, those twenty minutes of discord disappear; they are just apparently present because of our change in position relative to the  sidereal clock.

The moon is in the seventh house? Yes. Every night for a while. When Jupiter aligns with Mars? That means that one is above the other in a vertical direction. That happens every twenty-seven months. The Age of Aquarius? It has everything to do with the precession of the equinoxes, to be sure, but let’s do that tomorrow. Today our condolences to every Libra—or Leo, or Aquarius, for that matter. If constellations are responsible for our characters, we’d better talk seriously to our astrologer.
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Image credits: Libra: Skywatching, Daviod H. Levy, Time/Life Books, 1994, p. 183. Top: Wikipedia (link). On that site you can see it spinning—but keep in mind that the bottom of the axis also describes a circle in the case of the earth.

I found the site Astroplot (link) helpful in sorting actual versus astrological dates. And Precession of the Equinoxes, by Roy Taylor (link) is a very good all-around explanation.