Okay, let's jump in with part 2 of my #aspects in #astrology mega thread. Yesterday I spoke about aspects being visual relationships between planets, and that visual connection is what makes them "work," conceptually. We don't actually know what the mechanism is.
The mechanism by which astrology works is NOT SOMETHING I AM TALKING ABOUT TODAY PLEASE & THANK, I'm much more interested in digging into the ways in which the glances that the planets ping back and forth to one another in the heavens manifest.
Remember from everything I said last night: each planet casts seven glances, or aspects. A planet can observe anything where one of its glances falls in the Zodiac, as well as the sign it is in at the time. So each planet can behold eight spots.
But a planet does not interact with another planet unless that other planet is in range of the width of that planet's aspect. This is where we get into the discussion of orbs, and where I realize I need to make more roughshod graphics. Bear with me.
Remember the difference between lux and lumen? Lux is what's visible, lumen is what's ethereal. Look at a picture of a candle flame (and I'm indebted to @wadecaves and Deb Houlding for this example). 
Do you see how there's the bright flame in the center with a clearly delineated visual boundary, but there's this diffuse glow spreading out from it? Do you also see how the candle wax is gently illuminated? The light of the flame itself is lux, the diffuse glow is lumen.
Consider too that the Sun fills the whole solar system with light, but we don't see that light unless we're looking directly at the Sun (lux—and this is a bad idea, please don't blind yourself), or unless we're looking at something reflecting the Sun's light.
So in astrology, each planet demonstrates this difference between lux and lumen. And the difference between lux and lumen is the difference between an aspect and the _orb_ of an aspect. In Latin, aspect orbs are called "orbes stellae luminis," or "orbs of stellar lumen."
(That's directly out of the Bodier text I'm translating—I'll give you chapter and verse later.) So, returning to our example of Mars, we consider that Mars has an aspect, that is Mars' lux, and orbs of lumen on either side of that aspect. Comme çi:
This would be the same situation in any of the signs that Aquarius can behold: Aries, Taurus, Gemini, Leo, Libra, Scorpio, and Sagittarius. Mars' aspects in each of those signs is surrounded by this 14º wide ball of lumen.
Mars lumen extends 7º in front of and behind him, per Lilly. Orb sizes vary. The size of a planet's orb is related to its distance from the Earth, with the exception of the Sun and Moon. Practitioners use varying orbs but what is important is that they are applied consistently.
IMPORTANT: Things that do not emit light do not cast aspects and do not have orbs. So, the nodes, the Arabic parts, the angle degrees (Asc/MC/Dsc/IC), and house cusps do not generate aspects. Those points can only receive aspects generated by light-bearing bodies.
Needlepoint that on a pillow and keep it on your couch. No light, no aspect!
So, how do aspects become active? They become active when the luminous orbs of two planets, either in body or by aspect (remember, Ptolemaic aspects), begin to touch as the faster (or "lighter" one) moves forward towards the slower planet. Like this:
We say that the faster planet, which is Mars here, "applies" to Saturn. The Saturn glow here can either be the glow of lumen around the body of Saturn, or the lumen around one of Saturn's aspects. Saturn has an orb of 9º on either side, and he's at 29º here.
So Mars' and Saturn's aspects have just begun to mix together. Mars continues to move forward until such a time as he too hits 29º Aquarius (supposing Saturn isn't moving too—this is just for the sake of example). At that point, the aspect "perfects," and what it signifies...
...will become fully manifest. Like this:
What actually _happens_ as a result of this aspect perfecting depends on what houses the planets rule and what the nature of the aspect (whether it is harmonious & consonant or tense & dissonant) between them is. #aspects #astrology
Suppose this is a horary question about a job, and this aspect perfects as planned without any interruptions from other planets or one of the planets stationing retrograde and moving backwards before the aspect perfects (like "noooooope"-ing itself out of there).
Here's where aspects get really evocative. If Saturn rules the MC and Mars rules the Ascendant, in this case, the person will get the job as a result of their industry and diligence in pushing for the result they want, and the employer will see that and like it!
That's because Mars applying to Saturn from Aquarius is being received, but that's a whole other thread.
But say instead that Saturn rules the ascendant (so, Cap or Aquarius on the ascendant), and Mars rules the MC in Scorpio. In this instance, the job is basically in the querent's lap and the employer will take the initiative to seek them out to offer it to them.
The quality of the planets themselves and the aspects help us determine what will come to pass. I'm assuming this is a trine or sextile, but, if this aspect were an opposition or a square, I wouldn't be so positive, because both of the planets are malefics.
Trines don't always indicate _good_ things; Bernadette Brady describes them simply as representing that there is motion. All the wheels are greased and what is promised in the aspect will come to pass with ease. This is important to note.
Meanwhile, squares and oppositions don't always represent qualitatively _bad_ things; sometimes the tensions that they produce are creative. I'm speaking to this as someone with a partile-to-the-minute square between my Sun and my Ascendant ruler natally.
So aspects are either applying, perfecting, or separating. The Sun-Saturn square I have in my natal chart is applying. Applying aspects indicate what is to come, perfecting aspects indicate what is happening now (within the degree), separating aspects indicate what is past.
This is something that susses out a little more easily in horary and electional astrology than it does in natal or mundane work, but in my opinion the principle still remains true. Applying natal aspects will become more significant as you age. Separating will diminish.
Perfecting (within the degree) aspects natally, we might surmise, are keyed into who you are and will be more or less constant throughout your life. This is my working theory and I need to do more work to validate it for myself, but I believe the logic holds, considering horary.
So how do we interpret aspects? We need to take into consideration the natural significations of the planets and their condition first (whether dignified or debilitated, whether they're slow or fast, etc.), then the nature of the aspect itself.
Then we take all of the material we've derived from our technique, getting it as accurate as possible, and then put that in our black box symbolism machine called our "intuition" and see what lands. That's where astrology then really becomes a conversation with the moment:
Everyone born this week will have Venus applying to a conjunction to the sun, but everyone born this week will have Venus and the Sun ruling different houses in their charts and will be planted in different circumstances in which to grow up and manifest their natal promises.
(I've realized that these two tweet threads are basically a conference talk outline, or an introductory class lecture. Woof.)
