1. The Reason for Seasons

2. Seasons change on the Solstices and Equinoxes
These dates are only approximate…

3. SOLSTICES AND EQUINOXES
Time Zone: 6h 00m west of Greenwich
Vernal Summer Autumnal Winter
Equinox Solstice Equinox Solstice
Year Date Time Date Time Date Time Date Time
Mar 20 6: Jun 21 0: Sep 22 16:23 Dec 21 12:35
Mar 20 12:26 Jun 21 6: Sep 22 22:03 Dec 21 18:22
Mar 20 18:07 Jun 21 12:06 Sep 23 3: Dec 22 0:08
Mar 19 23:48 Jun 20 17:59 Sep 22 9: Dec 21 6:04
Mar 20 5: Jun 20 23:46 Sep 22 15:19 Dec 21 11:47
Mar 20 11:32 Jun 21 5: Sep 22 21:09 Dec 21 17:38
Mar 20 17:21 Jun 21 11:17 Sep 23 3: Dec 21 23:30
Mar 19 23:14 Jun 20 17:09 Sep 22 8: Dec 21 5:12
Mar 20 5: Jun 20 23:04 Sep 22 14:44 Dec 21 11:11
Mar 20 10:57 Jun 21 4: Sep 22 20:29 Dec 21 17:03
Mar 20 16:45 Jun 21 10:38 Sep 23 2: Dec 21 22:48
Mar 19 22:30 Jun 20 16:34 Sep 22 8: Dec 21 4:44
Mar 20 4: Jun 20 22:24 Sep 22 14:02 Dec 21 10:28
Mar 20 10:15 Jun 21 4: Sep 22 19:54 Dec 21 16:23
Mar 20 15:58 Jun 21 9: Sep 23 1: Dec 21 22:19
Mar 19 21:50 Jun 20 15:44 Sep 22 7: Dec 21 4:02
Mar 20 3: Jun 20 21:32 Sep 22 13:21 Dec 21 9:59
Mar 20 9: Jun 21 3: Sep 22 19:04 Dec 21 15:48
Mar 20 15:24 Jun 21 8: Sep 23 0: Dec 21 21:27
Mar 19 21:06 Jun 20 14:51 Sep 22 6: Dec 21 3:21
Mar 20 3: Jun 20 20:42 Sep 22 12:19 Dec 21 9:03

4. When is the Earth closest to the Sun?
July
October
January
April

5. When is the Earth closest to the Sun?
July
October
January
April

6. So what causes the seasons on Earth?
When is the Earth closest to the Sun?
July
October
January
April
So what causes the seasons on Earth?

7. Why are there seasons on Earth? The tilt of the Earth’s axis
Effect 1: Sunlight strikes the surface more directly in summer
 More energy per square meter is absorbed

8. Why are there seasons on Earth? The tilt of the Earth’s axis
Effect 2: The Sun is above the horizon longer in the summer
 More heating time each day

9. So are the summers hotter in the Southern Hemisphere?
(and winters colder?)
Notice much more land mass in the Northern Hemisphere
Much more water in the Southern Hemisphere
Water moderates temperature changes for two reasons:
1) The Sun warms water to a greater depth
2) Water has a higher specific heat

10. The Earth is a giant top, and it wobbles just like one.
Precession
The Earth is a giant top, and it wobbles just like one.
Precession takes 26,000 years to go through one full circle.

11. It’s winter in the northern hemisphere in January because
The southern hemisphere is then closer to the Sun than the northern hemisphere.
The Earth is furthest from the Sun in January.
The northern hemisphere gets no sunlight in January.
Sunlight strikes the northern hemisphere at a shallower angle in January.
Sunlight strikes the northern hemisphere more directly in January.

12. Astro-Cash Cab! Connor Voelkel Erin Henderson Carl Cook Michael Downs
Joseph Sanchez

13. 1) The first day of spring is called the is called the _______

14. 2) What value states your position on Earth east or west of the prime meridian?
Latitude
Longitude
Altitude
Azimuth
Elevation

15. 3) True or False?
At 37º north latitude, the north celestial pole would be 37º above the northern horizon.

16. 4) What season is it in the northern hemisphere in the diagram below?