Is the plane of rotation of the planets around the Sun , vertical of horizontal?
Depends on what you mean by vertical and what you mean by horizontal. The plane of the orbits falls into a sort of wide swath that is the same as the path that the sun appears to take as it crosses the sky from sunrise to sunset. This is called the plane of the ecliptic, and on any clear night you can find all of the planets that are not washed out by being close to the sun lying roughly in that plane. Some will be visible in the early evening – some will not rise until near morning. The apparent motion across the sky is due to the rotation of the earth on its axis, but the position is defined by the angle of the orbits relative to the angle of the earth as it spins. Pluto is sort of an exception, but it’s sort of an exception in other ways as well.
