Question

If you live in Earth's Northern Hemisphere, you expect the length of days to change from short in the winter to longest around the summer solstice, June 21st. This is MAINLY because A) the Earth's axis is tilted at about 23.5o. B) of the apparent counterclockwise movement of the Earth. C) of the elliptical orbit the Earth takes around the sun. D) the tilt of the Earth on its axis changes during the year.

Answer 1

The correct answer is "A) the Earth's axis is tilted at about 23.5o". When the Earth completes one revolution on its axis, we have one day; and when it completes one orbit around the sun, we have one year. Besides that, instead of being perpendicular to the sun, the axis of rotation is tilted permanently in 23.5 degrees angle.  This difference in the axis rotation angle causes the northern hemisphere to be exposed to the sun longer, increasing the duration of the day during the summer solstice.

Answer 2

The correct answer is (D) : The tilt of the Earth on its axis changes during the year.

Earth orbits around the Sun as well as spinning on the axis of its rotation once a day. As the Earth orbits the Sun, the tilt of Earth's axis stays lined up with the North Star hence the North Pole is tilted towards the Sun. The Northern Hemisphere is usually tilted toward the sun on the summer solstice while the southern hemisphere is tilted toward the sun on the winter solstice. Northern Hemisphere hence expects the length of days to change from short days in the winter and long days around the summer solstice on June 21st.