What's The Current Earth's Obliquity

 By: Adam Gregory
In the sector of astronomy axial tilt is also known as obliquity. The axial tilt is generally accepted to be the angle between the rotational axis and the line vertical to the orbital plane of an object. Now Earth's axial tilt is 23.4. The orbital plane of Earth is commonly known as ecliptic plane and the there's a different name for Earth's axial tilt 'obliquity of the ecliptic'.

This axis remains tilted in the same direction across the year. This means that when one hemisphere is indicating the sun during one half of the year then in the other 1/2 the other hemisphere will point towards the sun. This is the phenomenon behind the change of season. Whichever hemisphere is tilted towards the sun receives more amount of sunlight every day. Also at 12 noon the sunlight strikes at an angle which is closer to vertical, this results in more energy being received per unit area.

In Polar Regions the obliquity is really low this causes the Polar Regions to receive lesser solar radiation and the conditions become agreeable for the formation of glaciers. While at the regions close to the equator the axial tilt of the earth is bigger and therefore the daylight received is more in these regions. The Earth's axial tilt isn't a fixed quantity. It keeps changing and the cycle has a time period of approximately 41,000 years.

The awareness of Earth's axial tilt is very essential for making astronomic calculations and making findings from the outer surface of the Earth. In the 10th century, Abu Mahmud Khojandi measured the Earth's axial tilt. He made the measurements using the principle with a giant sextant. He discovered that the value of the tilt was lower than those measured by earlier astronomers ; he so concluded that the Earth's axial tilt isn't a continued quantity.

The earth's axial tilt varies between 22.1 and 24.5. At present the tilt is decreasing. In addition to this steady decline in the value of the tilt there are 1 or 2 smaller short term divergences. These are known as nutations and are principally caused by the changes in the plane of the orbit of the moon. This phenomenon can change Earth's axial tilt by about 0.005 degrees in plus or minus.

The four seasons that we experience are a result of the Earth's axial tilt. Together with the earth's revolution around the sun the seasons are also caused by the axial tilt of the earth.

At the end of the nineteenth century Simon Newcomb worked out the Earth's axial tilt and found that the value is 23 27' 8.26". This worth was accepted until improved telescopes were developed. These telescopes authorized more correct observations to be made. The electronic computers allowed more elaborate models to be made which could enable better and more exact calculations. In the year 1976 Lieske developed an updated model which had an axial tilt equal to twenty-three 26' 21.448". This model has become a part of the estimation formula that has been advised by the World Astronomical Union in the year 2k.
Artice Source: http://www.articlesphere.com
Article Tags: earth, planet, world, obliquity, tilt

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