For some reason last week's post got a lot of attention, so this became a busy week. Find the complete list on the Q&A page.
1) Were there larger stars in the distant past ?
2) Were there larger planets in the distant past ?
3) Have we detected aliens ?
4) Why shouldn't we assume mysterious signals are aliens ?
Because we don't know what alien signals would look like.
5) Why are we assuming aliens would communicate using technologies we can detect ?
The clue is in the question.
6) How come I can see Polaris all year round ?
7) Is the expansion of the Universe really like a balloon ?
8) Do gravitational waves cause winds in space ?
9) Will the collision of the Milky Way and Andromeda cause dangerous gravitational waves ?
10) Was Praxis, the Klingon moon, destroyed by a gravitational wave ?
11) Why do different planets move at different speeds ?
A wizard did it.