This question may require the use of the Earth
Science Reference Tables.|
Which observation provides the best evidence that Earth rotates?
The position of the planets among the stars changes during the year.
The location of the constellations in relationship to Polaris changes from month to month.
The length of the shadow cast by a flagpole at noontime changes from season to season.
The direction of swing of a freely swinging pendulum changes during the day.
Correct Answer Number: 4
Explanation: Rotation means to spin on an axis. For Earth, rotation causes night and day (24 hour period). The Foucault pendulum as stated in choice #4 is a good indicator that the earth rotates even though one cannot feel it. The pendulum looks similar to the arm of a grandfather clock and swings freely in a circular pattern. As the arm swings it will knock over pegs that are place in 15-degree increments around the perimeter of the circle. The pegs are knocked over, every hour for 24 hours. This leads to the notion that if 24 pegs, which are 15 degrees apart, are knocked over the earth makes one rotation in that amount of time (24 x 15 = 360).