Why Earth has seasons
1 min 39 s. The words are spoken and shown in the picture; the player can also show them as subtitles.
For the Earth and Space Sciences Regents. Topic: Axial tilt and seasons, with the past questions on it.
What Dr. Mars says (the words of the video)
Why does Earth have seasons?
Earth goes around the Sun once a year.
Watch the axis: it stays tilted the same way.
Earth's axis is tilted twenty-three and a half degrees.
It always points the same way in space.
In June, the Northern Hemisphere leans toward the Sun.
Dr. Mars measures a high noon Sun in New York: more direct rays, longer days.
In December, the Northern Hemisphere leans away from the Sun.
Now the noon Sun is low: rays spread out, shorter days.
In March and September, neither hemisphere leans toward the Sun.
Day and night are about equal in length.
Seasons come from the tilt, not from distance to the Sun.
Earth is closest to the Sun in early January.
A second cycle: the Moon. The Sun always lights half of it.
As the Moon orbits Earth, we see a changing part of that lit half.
Check yourself! At which position is it summer in New York: A, B, or C?
Think about which hemisphere leans toward the Sun.
Answer: A! The Northern Hemisphere leans toward the Sun there.
That is when Dr. Mars measured the highest noon Sun.
Dr. Mars. Free practice for the New York Earth and Space Sciences Regents.