Day length varies around the world depending on the time of year. The summer solstice, which occurs around June 21st in the northern hemisphere, is the longest day of the year. It marks the first day of summer. However, the exact day and time of the earliest sunrise and the latest sunset varies from city to city.
On the summer solstice, areas along the equator receive 12 hours of daylight. Meanwhile, the poles experience the most extreme variation. In the North Pole, there are 24 hours of daylight, one full day without night! Conversely, the South Pole experiences 24 hours of darkness.
The winter solstice is the shortest day and longest night of the year. This year, it will occur on December 21st in the northern hemisphere. On this day, the sun reaches its lowest point in the sky before setting. The winter solstice signals the first day of winter.
How It Occurs
Due to the earth’s axial tilt, the winter and summer solstice are reversed in the northern and southern hemispheres. As the earth rotates around the sun, it also spins on its axis and reverses the side of the earth facing the sun. The side of the earth leaning nearest to the sun receives the most light and the longest days, while the opposite pole is at its furthest from the light and warmth of the sun. When the first day of winter occurs in the northern hemisphere, it is also the first day of summer in the southern hemisphere.
Where It Occurs
The earth’s axial tilt causes the poles and those countries nearest to each pole to experience the most extreme variation in day length. Countries such as Norway, Iceland, Denmark, Russia, the U.S., Canada, Siberia, Scandanavia, Sweden, and Finland all witness the dramatic effects of summer and winter solstice on daylight hours. The parts of these countries which fall within the Arctic Circle are affected. However, no countries enter the Antarctic Circle, so there are no other countries in the southern hemisphere which experience this phenomenon.
The Arctic and Antarctic circles are 66.5 degrees from the equator. Areas approaching either pole have longer periods of day or night than those areas bordering the circle. These places have a phenomenon called the “midnight sun,” a term referring to times when the sun never falls below the horizon, allowing sunlight even at midnight. Some areas can have sunlight for 6 months of the year, and night for the other 6 months. Parts of Finland and Norway are among the most affected. Parts of Finland can have permanent daylight for 73 days during the summer. Areas in Norway may experience 24 hour daylight from April 19 though the 23rd of August. In winter, these areas have “polar night,” when the sun does not rise.
Places within 5 degrees of the Arctic Circles, or 60 degrees from the equator, may experience “white nights.” This is a time when the sun remains at the horizon line, creating twilight instead of night. White nights may only last close to 3 weeks.
Effect On People
St. Petersburg, Russia, has festivals to celebrate white nights for 10 days at the end of June. Jewish religious tradition has also been affected as many of their prayer times and rituals depend on recurring regular days and nights. Jews living in affected regions may conform to different standards in order to accommodate the variation.
Personality may also be affected, and people sometimes experience irritability or restlessness. Some develop insomnia or a condition called hypomania, which is characterized by an increase in energy levels and a feeling of euphoria often seen in people with bipolar disorder. People with hypomania during the light seasons are more prone to depression during the dark months. However, many more people are prone to decreased energy and lower mood during the polar nights or acquiring S.A.D. (seasonal affective disorder).
Effect On The Environment
Despite a lack of trees in the Arctic Circle, many plants and wildlife thrive in this environment. A large portion of land within the circle is designated for wildlife or state parks to protect the biodiversity. Before its numerous resources were discovered, only indigenous peoples lived within its borders. As few people have lived in these extreme and cold areas, natural resources are abundant. Somehave tried drilling under Alaska to access its oil reserves, and Russia depends on northern Siberia for 78% of her oil imports and 84% of her natural gas. Industrialization has been encroaching on the area to facilitate drilling and control of these supplies, but pollution due to these endeavors has been disastrous and is still increasing.
I belive every were can be depending on the time and season.
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