And I do not write, prove, because finding proof is hard.

Topic Question Example
 Sun & Moon How does the angular size of the Sun does not change?  
  How can we see the sun move at the same speed in winter, as in summer on the equator  
  What causes solar/lunar eclipses  
  How are we able to predict solar eclipses and equinoxes, which are based on mathematical formulas and a globe model.  
  How do seasons work, why is there a difference in southern and northern summers/winters?  
  How can we see the same angle to sun and moon on  
Stars and planets
How do southern hemisphere stars revolve around a single point and see the same star pattern everywhere on the southern hemisphere  
  What is the mathematics behind the movement of the stars and celestial bodies?  
  Where did Aristarchus, Eratosthenes and Kepler go wrong in calculating the distances between celestial objects?  
Maps  Why is it impossible to create a (flat) map with both distance and angles correct?  
  How can current models work (google maps/earth, Stellarium, SolarSystemScope)?  
  How does GPS and Glonass work?  
Gravity  Why is there gravity?  
  If everything we observe about the solar (the path of the planets around the sun, and moons around the planets), why does that not apply to us (i.e. Gravity)?  
  Why is there a direction of gravity?  
  How do tides work?  
Density and Buoyancy  Why is there a direction? And why is this direction up/down and not any other direction?  
  What is the force causing this?  
Curvature  Why do we see curvature in viewing mountains at a distance, that cannot be explained on a flat earth, even with extreme refraction?  
  Why do we see only the top of ships and lighthouses and not the bottom, unless they are compressed  
  How does refraction work on a flat-earth, as the layers of air are not bend and light should travel straight through these layers  
Seismology  How does sound travel through the earth, from one place to another, from any spot on the earth to the opposite spot, regardless of the position on the globe ?  
  How do earthquakes sound maps go around the globe, and around again? Do Earthquakes (dis)prove Flat Earth?
Magnetic Field  How do compasses work on a flat-earth model?  
  Why do we need different compasses on the southern and northern hemisphere, to compensate the tilt  
  How is earth's magnetic field generated?