On any given day, why does the photoperiod vary throughout the world?
I have no idea about what they're asking? :S
Start with these definitions of photoperiod.
http://www.google.com/search?hl=en&defl=en&q=define:Photoperiod&sa=X&ei=HGdYTeDBA8m4tweFqqzMDA&sqi=2&ved=0CBMQkAE
Then think about the rotation of the earth.
Is it because when one part of the earth is facing the sun they go throught daylight and other side go through darkness?
I'm totally not understanding this.
The sun reaches its northernmost point over the Tropic of Cancer in June. At that time, the north Polar regions receive 24 hours of daylight and the south Polar regions receive 24 hours of darkness.
The photoperiod refers to the duration of time in a day when there is sunlight. It varies throughout the world because the Earth is spherical and tilted on its axis. This axial tilt causes the angle of incidence of sunlight to change at different latitudes and seasons, resulting in variations in the photoperiod.
To understand this concept better, you can consider the following steps:
1. Start by visualizing the Earth as a globe.
2. Picture an imaginary line passing through the North and South Poles, known as the Earth's axis. This is the line around which the Earth rotates.
3. Now, imagine the Earth is tilted on this axis by about 23.5 degrees relative to its orbit around the Sun.
4. As the Earth orbits the Sun, different parts of the Earth receive varying amounts of sunlight due to this tilt.
5. During the summer solstice, the hemisphere tilted towards the Sun experiences longer days and shorter nights, resulting in a longer photoperiod.
6. Conversely, during the winter solstice, the hemisphere tilted away from the Sun experiences shorter days and longer nights, resulting in a shorter photoperiod.
7. The equinoxes, which occur in spring and autumn, are the times when the day and night are of equal length in all parts of the Earth.
Understanding the Earth's axial tilt and its impact on the angle of sunlight hitting different latitudes will help you grasp why the photoperiod varies throughout the world.