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Happy Summer Solstice

posted Jun 20, 2012, 8:03 PM by Anthony Pisano
At 7:09 PM EST today we will mark the official start of summer and the longest day (day light hours) in the Northern hemisphere. 

Now let's look at some interesting facts. 

Day Length in the following cities today:
Stockholm, Sweden: 18h 27m
Moscow, Russia: 17h 24m
Berlin, Germany: 16h 50m
Toronto, Canada: 15h 27m
Washington, DC: 14h 54m
Tokyo, Japan: 14h 35m
Mumbai, India: 13h 27m
Singapore: 12h 12m
Sydney, Australia: 9h 54m

As you can see day length depends on the latitude. Also at more northern latitudes the Sun is above the horizon for longer while at lower latitudes the amount of daylight is shorter, but the Sun climbs higher in the Sky. 

If June 20 is the day when we receive the most sunshine, why is it regarded as thebeginning of summer and not its peak? And similarly, why is December 21, the day of least sunshine, the beginning of winter and not mid-winter day?

Blame the oceans, which heat up and cool down only slowly. By June 21 they are still cool from the winter time, and that delays the peak heat by about a month and a half. Similarly, in December the water still holds warmth from the summer, and the coldest days are still (on the average--not always! ) a month and a half ahead.

Every planet in our solar system has seasons. But the seasons that occur on other planets are extremely different from the traditional spring, summer, fall and winter that we experience here on Earth. Despite what may seem like great variations in temperature, weather and climactic conditions in different places around the globe, in reality, there actually is little variation in Earth's overall climate. Why?

There are two reasons that seasons occur on the planets: the tilt of a planet's axis and its orbit around the Sun. Our orbit is nearly circular, so there is little variation in Earth's overall climate. But, other planets have more elliptical - egg-shaped - orbits, and therefore their seasons are very different than what we experience. The terms "summer" and "winter" tend to be Earth-oriented terms, but can be applied to the other planets as well. When the North Pole of any planet is tilted toward the Sun, astronomers call it the Winter Solstice; when the South Pole is tilted toward the Sun it's called the Summer Solstice.

Now go and enjoy this beautiful day today!