1. The Earth and its Motions
Science 8
Astronomy Notes Page 6

2. The Earth and its Motions
The Earth rotates or spins on its axis
The rotation time is 24 hours or 1 day

3. The Earth and its Motions
The Earth revolves or travels around the sun
The revolution time is 365 ¼ days or 1 year
Ever wonder what leap year is or why is there are 29 days this month? Click here…

4. The Earth and its Motions
The Earth does not stand straight up on its axis
The Earth is tilted at an angle of ½° on its axis.
Why is 23 ½° North or South of the Equator significant?

5. Putting it all together…
What causes day and night?
The Earth’s rotation and its spherical shape causes half of the Earth to face the sun (day) and half to face away (night).
DAY
NIGHT

6. Putting it all together…
What causes seasons?
The Earth’s revolution and its tilt on its axis causes the sun to hit certain parts of the Earth more directly (summer) and parts less directly (winter).

7. The Winter Solstice Is the 1st day of winter Minimum hours of daylight
Happens around December 21st (in the Northern Hemisphere)
Most direct rays hit south of the Equator (at 23 ½° S)

8. The Summer Solstice Is the 1st day of summer Maximum hours of daylight
Happens around June 21st (in the Northern Hemisphere)
Most direct rays hit north of the equator (at 23 ½ °N)

9. The Vernal Equinox Is the 1st day of spring
Equal hours of daylight and darkness
Happens around March 21st (in the Northern Hemisphere)

10. The Autumnal Equinox Is the 1st day of autumn (fall)
Equal hours of daylight and darkness
Happens around September 21st (in the Northern Hemisphere)