I’m learning about transits & aspects. I got to thinking…if Mercury & Pluto & the Vertex, et al affect me as they aspect my natal chart, how does the Earth affect me on a daily basis? Is my natal chart basically considered “Earth”?
You are based ON the planet called Earth, so it cannot transit you. The natal chart is calculated using geographical reference points based on your location at birth ON the Earth and the planets are recorded as to their positions in space on that day/time in relation to that geographical position.
So in that sense the chart is calculated on the basis that you are the Earth in that moment of time you incarnated in a physical body. Our bodies are connected to the Earth in terms of matter, they consist of cells, minerals, water, etc. We are affected by the energies of the Earth while we live upon it, the Earth is affected by us, and in turn we are all affected by the cosmos we reside in, everything is connected. It's helpful to develop your relationship with the Earth considering this powerful connection.
That is an extremely elegant explanation. I especially like how you put this:
The Earth effects us by rotating on its axis thru all 12 signs on a daily cycle. It is like a distributor in an old style engine.
Of course I don't know diddly about car engines, but I just watched a couple youtube videos (my grandfather would be proud), and I think it makes sense! I used to think of the zodiac as a sort of randomization machine. But now with your analogy, I can see how it's a more orderly process.
I don't totally understand the conduit thru our MC/IC but I will try some more to visualize it... I also love this:
There is breathing happening thru the Earth that reanimates us daily.
I strongly believe in the power of the sun's rhythm (and the moon's monthly rhythm for women).
Thank you! @don
The highest point the Sun reaches in the sky on our day of birth indicates the Midheaven. The opposite point is the IC or Nadir. The two together define the Meridian - an imaginary north south line on the Earth's surface that connects both geographic poles. It indicates the longitude at our place of birth.
In our solar system - most planets move within the confines of the horizontal plane of the ecliptic. The geographic poles of the Earth and our Midheaven /IC chart angles are vertical - up and down to the ecliptic.
When we get to working with the IC in particular - it is Moon related root hunger and needs darkness to germinate and emerge.
@don Thank you, that is so helpful. My midheaven is at 1d Aries, and my husband's sun is conjunct my IC, so this info is of particular interest to me... You clarified a lot, and inspired me to read some articles with diagrams. I really enjoy learning how to orient myself physically with respect to the heavens. I have always loved geometry, but I've never tried drawing my chart with a compass and a straight edge. Now I really want to!
My balsamic Moon in Sag conjunct the GC trine Pisces Chiron conjunct the IC is singing along. 
Thank you for sketching this out so clearly.
@don My Midheaven is 27 Gemini and my IC 27 Sagittarius which is very close to the degrees of Polaris and the Sag black hole on the world's axis as you were describing. I wonder if this relates to why my interest in astrology is weighted towards the energetic and is interwoven with my interest in human evolution on a soul level. Of course lots of factors to consider but when I read that I felt even more like an arial or antennae! I note that Neptune is squaring those degrees, thus the axis, from Pisces last year and this, I really enjoyed the transit to my DC at 27 also, because I felt so tuned in and supported by the universe. Hopefully it's positive for the collective too.
That is a potent IC. The galactic Black Hole carries the feminine creative force and gnosis of the physical universe. It is related to emotion and gravity as opposed to the Sun which is spirit and light . The other ally to the Galactic Center in our individual charts is the lunar apogee - the Black Moon.
@don I'm starting to get a feel for the framework you are describing. I'm wondering how does Uranus link to the IC?
@sophiab ,
If the Midheaven is defined by the highest point the Sun reaches in the sky on the day of birth - the IC describes the nite sky after 12 hours of the Earths rotation. Uranus is the nite sky.