The Equation of time

Use the graph on the equation of time page to answer the following.

A person lives in Greenwich. In their garden they put a stick vertically in the ground and over the course of a day they measure the length of the shadow produced by the stick.

On a certain day the shadow is shortest at 12:14pm

1. How many minutes behind is the shadow stick?

2. What month do you think this day was in?

3. In what months might the shadow be shortest before 11:50am?

On a particular day in May the equation of time = 4 minutes.

4. At what time will the shadow be shortest?

5. If you moved 100 miles East will the sunrise happen sooner or later?

6. For every degree of longitude you go how many minutes earlier does it happen?

7. For every degree west you go how many minutes later does it happen?

The captain of a ship leaves England heading west with a watch that accurately tells him GMT. A week later he finds that the Sun is at its highest at 12:24p.m. The equation of time on this day =0.

8. How many degrees west has he travelled?

9. If the equation of time on this day was 7 minutes at what time would the Sun culminate?

9. Why did the measurement of longitude rely on the invention of accurate portable timepieces?