To give you an idea of the dangers involved in using any sort of "ladder," let's work our way through a simple example. It's difficult to perform astronomical observations during the day, and inside a classroom, so we'll make an analogy: instead of distances, we'll measure volumes of
Your goal is to figure out how many spoons it would take to fill the big storage container. In astronomy, we use a method involving nearby objects to calibrate a second method which applies to distant objects; in this example, we'll use a method involving small objects to calibrate the volume of bigger objects.
You can perform these steps inside the classroom:
For the final step, please go outside, so that we can use a hose and spill water on the ground. Because the final step involves a difficult measurement with big instruments -- like using the Subaru or Keck telescopes -- you only get 1 attempt per team. You'll have to estimate the uncertainty as you go.
When every team has finished, we'll compare all the values. I wonder if the values will agree with each other ....