Children in a car
Horizontal
During a car trip children can be enjoyed with mathematical concepts.
They can observe the following things.
A turn to the left or right.
A straight line.
S-curve with an inflection point.
More difficult are
Bend at its sharpest or strongest curvature.
Northernmost point (or other direction).
Point closest to the sun or moon.
Vertical
In hilly or mountainous landscape possibilities are extensive.
The road is horizontal, climbing or descending.
The steepness increases, decrease or remain the same.
Greatest slope up or down; inflection point.
Peak or valley.
Pass and saddle point (in the direction of a top valley).
Sometimes horizontal and vertical events happen simultaneously.
Planet Movement
If you drive in a bend, try to keep an eye on a tree trunk.
It moves relative to the background.
You'll see when you pass the tree,
the direction of movement of the tree reverses relative to the background.
It moves 'retrograde'.
In the same way, the temporary backwards motion of the planets
relative to the star background is explained.
Because the speed of the planet is not as great as the pace of the
Earth, the direction of the line Planet Earth is always changing.
The planet reaches a reversal point when the earth goes straight to it or
when the earth moves away from it straightly.