What was going in the very early universe? How does inflation provide the seeds of larger structures?
What are some weaknesses with the standard Big Bang model? What are the horizon and flatness problems? How does accelerated expansion solve these?
What is the cosmological constant? How is the expansion of the universe related to quantum fields? How does a vacuum energy produce accelerated expansion?
What is a quantum state? How can two particles share the same state? What is entanglement, and does it really allow for faster-than-light communication?
Were the dark ages really dark? What is a perturbation, and how did they grow in the early universe?
What does momentum have to do with rockets? Why are nozzles so dang important?
What is the so-called “OMG Particle”? Where could it possibly come from, and how are magnetic fields involved? How can we detect these cosmic rays?
Seriously, What is Gravity? Another story of gravity about How did Einstein develop General Relativity? What does it mean for different kinds of masses to be equivalent? How does gravity do what it does? Why is curvature so important in understanding gravity?