Solar. Wind. Batteries. Nuclear. Geothermal. Reduction. Anything energy related!
Discuss modern energy, especially in the context of renewables, using less energy, and the likely futures coming. This isn’t the place to just blindly say that, of course, fusion will happen, see, it’s only 10 years away (as it’s been for the past 60 years), and that anything that means we’ll have to use less energy is unthinkable so therefore cannot happen. Wrong place for that!