Is the universe infinite? What about the cosmological horizons, the limits to what we can see? Will we ever know for sure what’s beyond them?
Why did we develop the International Space Station in the first place? What have we learned in its 25+ years of operation? When is it coming down, and why? And what’s coming up next?
How do particle colliders work? What kinds of energies are we talking about? Are there any uses for colliders except for physics experiments?
What are some sources of gravitational waves that aren’t black holes? How did inflation create gravitational waves? How can we possibly detect them?
How do we measure the sizes of stars? What are the biggest ones today, and how big could stars have gotten in the past? Is there any way for a star to cheat and get even bigger?