Why There Are Four Seasons

Caleb Quick

9/19/12

Seasons

The Earth's Seasons

The seasons are not due to the difference in the amount of space between the Earth at any given point in comparison to the other points of Earth from the sun. The seasons are actually exist due of the fact that the Earth's axis isn't on a perpendicular plane from the plane of Earth's orbit, but on a plane that is perpendicular to an inclination of the plane of Earth's orbit around the sun of 23 1/2 degrees. During summer in the northern hemisphere of Earth, the northern hemisphere is inclined towards the sun, so as a result the southern hemisphere is inclined away from the sun and will recieve less direct sunlight as a result of the spherical shape of Earth. Because the Earth is spherical the southern hemisphere will be curved away from the sun and back behind the northern parts of the Earth. During this time the northern hemisphere will experience summer and the southern hemisphere will experience winter. As the Earth revolves throughout its orbit, the axis will stay inclined in the same direction but the Earth will be changing its position in reference to the sun. As a result of this from our reference point we would experience the same thing if Earth'e axis rotated and slowly moved the northern and southern points in circles that took the same amount of time as the Earth revolving once through its orbit or one year*. The sun crosses** the equator on about the twenty-second of March from north to south. This is known as the vernal equinox. During the vernal equinox the days and the nights are equal in length and the northern and southern hemispheres are in an equal state of direct sunlight so it could be viewed as a neutral season or a transitional season. There is also an autumnal equinox which is essentially the same thing as the vernal equinox but it occurs around the twenty-second of September. There are also solstices which are the start of summer and winter which will occur around three months before or after an equinox. During the solstice the days and nights last the greatest difference in time compared to any other day of the year. These dates do not occur exactly on the twenty-second of every third month because the calendar doesn't have exactly the same as year or day as what a year or day is exactly scientifically. Since the seasons aren't affected by the distance from the sun only by the change in direct sunlight everywhere that isn't on the Earth's equator will experience four seasons. Location can effect the distinction between these seasons though because the change may be very subtle and too subtle to realize but it exists scientifically because of the revolution of the Earth and the constant angle of the Earth's axis.

*This picture represents the Earth rotating and its axis moving in circles. From our refrence point the Earth might as well do this to change the seasons and have the same effect.

** The sun doesn't actually move when it "crosses" the equator but from Earth it appears as it does and would have the same effect. The Earth's revolution is changing where the axis is pointing and will cause the most direct point of sunlight to shift north and south on the Earth over time.