How far away are the planets from the sun?  
Students took beach ball planets outside today and estimated how far they thought each planet was away from the sun and from neighbouring planets.  We talked about comparing the relative distances. They were surprised how "close" the inner planets are compared to the lonely outer planets!

Estimating the planets' relative distances from the sun.
Those not in line with the planets represent the asteroid belt.

Actual relative distances from the sun.