The sun, moon and planets all follow approximately the same path from east to west across the sky; none of them is ever seen in the far northern or far southern sky. What does this suggest about the arrangements of these members of the solar system in space?
Think of terms of the plane in which each planet and moon moves, in relation to the Earth's orbital plane. That should give you a clue. Another important factor is that the earth's axis is only tilted 23 degrees away from a perpendicular to its orbital plane.
Planets and the moon certainly DO appear in the southern sky once a day from the northern hemisphere. What the question really means to say is that they do not appear anywhere close to the north or south celestial poles, which are the directions to which the polar axis points.
Look at a diagram of the solar system as you ask your question out loud. Think about what the sky would look like if you were standing on the equator, and then each of the poles.
The fact that the sun, moon, and planets all follow a similar path from east to west across the sky implies that they are all located within the same plane known as the "ecliptic." This plane is essentially the Earth's orbital plane around the sun.
To understand this concept, you can visualize the solar system as a flat disk where the sun is at the center and the planets orbit around it. This disk represents the ecliptic. The Earth's orbit is also in this plane, and as a result, the sun, moon, and planets all appear to move in the east-west direction as seen from Earth.
Now, let's consider the Earth's axial tilt. The Earth's axis is tilted about 23 degrees away from a perpendicular to its orbital plane. This tilt gives rise to the changing seasons on Earth. However, it also affects our view of the sky.
Imagine standing on the equator and observing the sky. You would see the sun, moon, and planets travel across the sky from east to west, passing through the zenith at some point during the day. Now, if you move towards the poles, the view changes. At the north pole, for example, the celestial pole is directly overhead, and everything else appears to move in a circle parallel to the horizon. This means that objects near the celestial pole, including the sun, moon, and planets, never rise too high in the sky in the northern hemisphere. The same applies to the southern hemisphere's view from the south pole.
So, while it's not accurate to say that planets and the moon never appear in the southern or northern sky, the question likely refers to their absence near the north and south celestial poles – the directions to which Earth's polar axis points.
In conclusion, the consistent east-west motion of the sun, moon, and planets across the sky, combined with the Earth's axial tilt, suggests that all members of the solar system lie within a common plane - the ecliptic.