We now travel back to the date, time and location of your birth. The very moment you take your first breath we pause. We imagine that at in that instant everything around you freezes. This means everything from you to the ends of the universe itself is suspended where it was in that instant. Keeping that self centric point of view in mind- you begin to look around you. In different directions you see the sun, moon and all the planets, frozen in place. Next you notice the constellations of the zodiac as well, all 12 signs creating the starry backdrop where the planets sit.
Imagine that there is a direct line connecting you to every planet. A direct line like that ray of sun light. A direct line in the form of a moon beam. Whatever the physical make up of it, there is a direct connection between you and each of these planets in that moment of birth. The same goes for the constellations.
As you look out towards each of the 12 signs surrounding you, there may or may not be a planet in that same direction. In some cases the planets will be scattered evenly in different directions, falling in front of various signs. In other cases they may seem to be bunched up in groups, all landing in the direction of the same sign. Where they’ve landed in this frozen moment in time, from your point of view, is how we decide that your Sun is “in” Aries. Or your Mars is “in” Pisces. It means that from your view point you are looking at the sun and further on the constellation of Aries. That direct line from the Sun to you is overlapping with and combining with the direct stream from Aries. When you look towards Mars, it is the constellation of Pisces that is the backdrop.
This is what it means when a planet is in a sign. The planet being in the sign essentially means that the behaviors or actions represented by that planet will be colored by the traits of that sign. Ex: you will express Mars behaviors in a Piscean way. The planets are always in a sign. But a sign does not necessarily always have a planet in it, due to the obvious that there are less planets than signs.