Geology, palaeontology, archaeology, atmospheric science, climate, climate change and meteorology...
At what altitude above the Earth is zero gravity experienced?
What's so special about the size of the Earth that makes life more likely?
If an asteroid wiped out the dinosaurs, but birds are dinosaurs, what the heck is going on?
How great is the damage humans are causing to the oceans by discharging so many chemicals and excreted drugs into them?
Why don't compasses point to East or West?
...and where does the sky end?
...and if so, why?
Could the testing of nuclear bombs lead to earthquakes?