Where is the Oort Cloud and what is it made of? Why do we think some comets from there? If the Oort Cloud exists, how did it form?
What makes time so hard to understand? Why is it so different from the spatial dimensions? Is time in any way connected to that most difficult of concepts, entropy?
How much energy is needed to blow up the sun? How is this connected to the idea of binding energy? Where is all the energy in the universe?
What do brown dwarfs teach about stars? What do they teach us about planets? What keeps them warm, and how long do they live?
What are the many sources of light in the universe? Why is a spectrum so important? What’s the difference between synchrotron and Cherenkov radiation? What’s the best word ever in physics?