* Orbital Planes: Each planet in our solar system orbits the Sun in a slightly different plane. Imagine them like slightly tilted plates, so they won't all line up perfectly.

* Orbital Periods: Planets have different orbital periods (the time it takes to go around the Sun). This means they are constantly shifting positions relative to each other.

However, there are moments when planets appear to be close together in the sky from our perspective on Earth:

* Conjunctions: This is when two planets appear close together in the sky. It's not a true alignment, but a visual effect.

* Planetary Alignments: These are rare events where several planets appear clustered together in a small area of the sky. Even these "alignments" aren't perfectly straight lines, but still a fascinating sight.

The order of planets from the Sun outward is:

1. Mercury

2. Venus

3. Earth

4. Mars

5. Jupiter

6. Saturn

7. Uranus

8. Neptune

To know when the planets are appearing close together in the sky, you can check online resources or astronomical calendars.