Summer Solstice 2012: What It Means And How It Works

Even though it is the day with the most sunlight, it does not mean that summer solstice will be the hottest day of the year. (Photo : Wikimedia Commons)

Summer is officially here, with summer solstice marking the beginning of summer and the longest day of the year for the Northern Hemisphere. Let's take a look at what exactly is summer solstice and why it occurs.

The reason for the solstice is because the Earth's north-south axis is tilted at approximately 23.4 degrees in relation to the plane of our solar system. Add our elliptical orbit around the sun into the equation, and this means that different parts of the Earth get different amounts of sunlight during different times of the year.

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During summer solstice in the Northern Hemisphere, the North Pole is tipped more towards the sun than during any other day of the year. This means that the Northern Hemisphere will receive the most sunlight, and thus have the longest day of the year.

This year, summer solstice arrives a day earlier than usual due to the fact that this year was a leap year, and since February got an extra day, it falls one day earlier in June. Either way, summer solstice almost always falls on June 20 or 21.

Summer solstice isn't always exactly on those dates, "but there's a bigger jump when you have a leap year," explained Mark Hammergren, an astronomer at the Adler Planetarium in Chicago to National Geographic.

At high noon, the sun will be at the highest point it can be in the sky for those along the Tropic of Cancer, meaning it will be directly above. For those at further latitudes, the sun will not appear to be directly overhead.

On the other hand, during winter solstice, the South Pole faces the sun, and while it marks the longest day of the year for those in the Southern Hemisphere (since it means the beginning of summer for them), it is the shortest day of the year for those in the Northern Hemisphere (who are about to experience winter).

Many festivals and rituals are held around the world during summer solstice.