The Seasons

The SeasonsWe 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 Suns rays hit the Tropic of Cancer directly.

The Tropic of Cancer is a line of latitude.WinterNotice here that the Suns 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. 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!

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.

Now lets look at all our SeasonsThe word equinox literally means equal night. During the Vernal and Autumnal Equinox, the Suns rays fall directly on the equator. We experience equal hours of darkness and sunlight.Vernal means Spring.Autumnal means Fall.

But what happens in the Summer?In the first slide we learned that the Suns 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.

Looking at the Winter SolsticeThe 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.

Putting it all togetherThe Earth rotates Counterclockwise around the Sun.Summer Solstice= June 21stAutumnal Equinox (Fall) =Sept 22ndWinter Solstice= Dec 21Vernal Equinox (spring)= March 21st

But what happens in the Southern HemisphereWhen 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 Earths axis.

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.

A Solar EclipseIn 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. A Lunar EclipseIn a Lunar Eclipse, the FULL Moon is in Earths Shadow. The Earth is between the Moon and Sun.

Again, you can see the area of total shadow is the umbra and the penumbra is only partially eclipsed.Solar and Lunar Eclipses

Umbra and PenumbraThe 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 Suns atmosphere).