Why didn’t the big bang collapse in a singularity? What would a universe-sized black hole be like? Now that I think about it, do we live inside a giant black hole already?
Could we nudge the orbit of the Earth to avoid the death of the Sun? Could it get kicked out of the solar system altogether? What are rogue exoplanets?
If light always travels at the speed of light, how does it slow down when passing through air or water? Does it matter if light is made of particles or waves? What’s the difference between phase velocity and group velocity, and how does that all play into this?
What are the biggest mysteries facing modern astronomers? What questions do I wish could be answered in my lifetime? What are most astronomers working on right now?
What discoveries and insights made the biggest impacts in astronomy and physics? What were the biggest surprises? What results took the longest to achieve?