How do cracks appear in spacetime? What does it have to do with symmetry?
Why is it so hard to predict solar eclipses? How did Newton and Halley team up to solve it? What have we learned from solar eclipses since then?
How hard is interstellar travel? What are the possible ways to achieve the required energy?
What’s the deal with redshift? How can we actually interpret velocities when it comes to cosmic expansion?
Is light made of waves or particles? Is matter made of waves or particles? What does it mean for matter to “wave”, anyway?