Why is the moon so special? Why do we think a giant impact created it? Why didn’t the same thing happen to other planets?
What is 21-cm radiation? What (and who) produces it? What causes it, and what does it tell us about the universe?
What is an Alcubierre warp drive? What would it take to make it work? Could it propel spacecraft even below the speed of light?
What is an axion? How could axions make a star, and what does that have to do with dark matter? What would these stars look like?
Where do parallel universes exist? Could we use wormholes to travel to them? What does time travel have to do with all this?