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Saturday, April 29, 2017

What's in a year?

A year is the time it takes for the Earth to make one revolution around the sun which is 365.2252 days. We compensate for the fraction by having an extra day on February 29th every four years. These are called leap years. Leap years do not occur at the turn of a century unless that century is divisible by 400 like 2000 was. Hence 2000 was a leap year.

What happens in a year depends on how far North or South of the Equator you are. If you live close to the equator, you have a year round summer. As you move North or South, you have seasons. Seasons in the Northern Hemisphere are the opposite of the Southern Hemisphere.

When the Northern Hemisphere has winter, the Southern Hemisphere has summer. Seasons are due to the tilt of the Earth. Some people mistakenly think that the distance from the sun causes seasons. It does not. It is the length of the day. Essentially, the longer the day, the more heat is gained. A longer day produces a shorter night when heat is lost. With more heat gained than lost, you have the heat of summer. The length of the day depends on the tilt of the Earth. Longer days occur when the respective hemisphere of the Earth is tilted toward the sun.

Now why don't you have really hot summers as you move toward the poles. Sunlight hits at an angle and is not as intense as a result. Sort of like pointing a flashlight directly on an object and pointing a flashlight at an angle. The direct beam is stronger. So even though you have excessively long days, the light is not as powerful.

The Earth does move closer to the Sun during the Northern Hemisphere's winter and Southern Hemisphere's summer. This is why the extreme of season's is not as harsh in the Northern Hemisphere as it is in the Southern Hemisphere. The Earth's orbit is elliptical.

1 comment:

  1. Hi Ann- interesting to have the 'year' explained quite so succinctly - really useful ... cheers Hilary

    http://positiveletters.blogspot.co.uk/2017/04/z-is-for-zebra-zoo-and-zedland.html

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