There is a term in astrology called ‘Black Moon Lilith’ that scares the pants off a lot of people with the mention of ‘Lilith’ (due to religious teachings/upbringing most likely), so let me explain a little about the ‘black moon’ in scientific terms.
Firstly – the Moon does not orbit about the centre point of the Earth. The earth and moon work as a two-body system, both spinning around a common centre of gravity. That’s what keeps the moon ‘attached’ to the earth. This centre-of-gravity point, about which they both turn, is called the Earth-Moon Barycenter – about 3,000 miles/4,700 km from the middle of the earth and so the earth wobbles around this off-centre point within itself. Plus because the moon also orbits the same point it has its unique wobble as well.
Then there is one more thing to consider. In reality, the moon experiences a stronger gravitational pull from the Sun than it does from the Earth and so this disturbs its orbit a lot, resulting in a lunar orbit which looks like an ellipse (oval shape) drawn with a wavy, wobbly line.
Astronomers have a term called the Mean Lunar Orbit that is a mathematical calculation to even out the wobbly line into a nice smooth ellipse, by averaging out the moon’s positions over time in order to make predictions about the moon’s ‘behaviour; eg. when there is going to be a Super Moon etc.
The term ‘mean’ in their dictionary needs to be interpreted as the ‘average’ (rather than ‘mean’, as in scrooge).
The apogee (farthest away from the earth) that the mean orbit is, is known as the Mean Lunar Apogee, or Mean Black Moon. In my interpretation, the ‘black’ is equating as being less under the influence of – on this occasion, the earth. Hence the fear of being out of control by the earth’s inhabitants; in chaos. We then have the term, Black Moon Lilith.
The BML completes the circuit of the zodiac in 9 years, staying approximately nine months in each zodiac sign; a gestation period. In an astrology horoscope, where the BML is located represents/points-to where we experience our greatest challenge to overcome ourselves in order to thrive; our weakest point.