The finish line in a race is there as a reference point for the racers, the judges and the audience. This is true for track and field, auto racing and horse racing. Its key characters? It is clearly defined and does not move. So as the race participants run over it,it is possible to determine who won the race. Likewise a controlled variable in any valid experiment is clearly defined and does not change. They are both static reference point.
Feel free to be the first
Please review the linked page for context.
If you can think of something better than this,
please add it to the database