Parallel vs. parallax

Parallel has always been a fun word for me.  I always wondered why the put the double l  in the middle of the world.

Parallax is a related almost opposite) word that ha the same double l .

Must people know the definition of parallel but here it is again.  Basically, if two lines are parallel, they are equal distance apart everywhere.   They run side-by-side and never intersect.

Parallax is a bit more complicated.  In general, it mean an apparent change in the position of an object resulting from a change in position of the observer. A good example is two people in different location in the world viewing a star.

I first heard of parallax in the context of viewing a gauge or dial. If you stand directly in front of it, you get a true reading.  If you move a foot or two to the side, you get a different and erroneous, reading.