Question

1) explain why we see the moon rise 52 minutes later each evening, and 2) explain why the moon looks different sizes over the course of a month.

Answer 1

1) Please refer to figure-1 and figure-2 below which are drwan at an interval of 24 hours.

The first figure shows a line joining you and the moon at an instant of time today.The moon completes 1 revolution i.e 360°in 27 days.In 1 day(24 hours) it would move by an anangle=360°÷27=13.3=13^°(approximately). And the earth completes 360^° in 1 day to come back to the same position.The very next day (after 24 hours) moon is ahead of your position as shown in figure-2.So, the moon is 13^° ahead of your position tomorrow at the same time.

The earth moves 360^°in 24h=24×60mintues=1440 minutes.

So, for completing 1^° earth would take 1440÷360=4minute.To catch up with the moon it has go 13^° extra .The time taken to do so =13×4=52 minutes.Therefore every other day we can see the moon 52 minutes later than we saw it the previous day.2) The moon goes around the earth along an elliptical path as shown in the diagram below.For some part of the month it is closer to the arth and appears bigger whereas at some other part of the month it is farther and hence appears smaller.