1. The Seasons
The Tropic of Cancer is a line of latitude.
We experience Seasons because the Earth does not receive the same amount of solar radiation at all times. When the Northern Hemisphere is tilted towards the Sun, we have Summer. The Sun’s rays hit the Tropic of Cancer directly.

2. Winter
Notice here that the Sun’s rays are shining directly on the Tropic of Capricorn in winter. At this time the Northern Hemisphere is tilted away from the Sun….But the Southern Hemisphere is not. They are experiencing their summer .
The Tropic of Capricorn is another line of latitude.

3. What happens at the Poles?
An interesting phenomenon occurs at the North Pole in the winter. When the Northern Hemisphere is tilted away from the Sun, the North pole receive little or NO sunlight!

4. Does this happen at the South Pole?
This can happen at the South Pole, too! In June, while we have our summer, the South pole is tiled away from the Sun and receives little or NO sunlight.

5. Now let’s look at all our Seasons
The word “equinox” literally means equal night. During the Vernal and Autumnal Equinox, the Sun’s rays fall directly on the equator. We experience equal hours of darkness and sunlight.
Vernal means Spring.
Autumnal means Fall.

6. But what happens in the Summer?
In the first slide we learned that the Sun’s rays fall directly on the Northern Hemisphere in the Summer. June 20th is called the Summer Solstice. At that time we have the largest number of daylight hours and the shortest number of hours of darkness.

7. Looking at the Winter Solstice
The winter solstice occurs on December 21st. At this time, the Northern Hemisphere is tilted away from the Sun and it receives the fewest hours of daylight and the largest numbers of hours of darkness.

8. Putting it all together
The Earth rotates Counterclockwise around the Sun.
Summer Solstice= June 21st
Autumnal Equinox (Fall) =Sept 22nd
Winter Solstice= Dec 21
Vernal Equinox (spring)= March 21st

9. But what happens in the Southern Hemisphere
When we put all these ideas together, we can also see that the Southern Hemisphere has Winter when we have Summer AND they have Summer when we have winter. This reversal of the seasons is due to the 23.5o tilt of Earth’s axis.

11. What happens during an ECLIPSE?
An eclipse means some celestial body is cast in shadow. A solar eclipse means the Sun is in a shadow. A Lunar eclipse means the Moon is cast in a shadow.

12. A Solar Eclipse
In a Solar eclipse, the NEW Moon is between the Sun and Earth.
The area of TOTAL shadow is called the Umbra. Think of an “umbrella” that shades you from sun or rain.
The area that is partially eclipsed is called the penumbra.

13. A Lunar Eclipse
Again, you can see the area of total shadow is the umbra and the penumbra is only partially eclipsed.
In a Lunar Eclipse, the FULL Moon is in Earth’s Shadow. The Earth is between the Moon and Sun.

14. Solar and Lunar Eclipses

15. Umbra and Penumbra
The previous simulation shows the umbra and penumbra formation. During a Lunar eclipse, the Moon often appears to be blood-red. In a solar eclipse, we can see the corona of the Sun (the outer edge of the Sun’s atmosphere).