How do black holes get close enough to merge? What causes them to emit gravitational waves, and where do the waves come from? What does the merger process look like?

How did Pluto get demoted? What makes a planet a planet anyway? Why do we now have so many different kinds of planets, and should we make things simpler?

How do gravitational lenses work? Where would a spacecraft need to be to use the Sun’s gravity as a telescope? What could we learn about exoplanets with this on weird trick?

What’s behind the Martian Methane Mystery? Is it a sign of life, or just some strange chemical process? Or are we just fooling ourselves?