Today is the first day of summer, which also marks the beginning of 2010’s Summer Solstice. This is basically the “a result of the Earth’s north-south axis being tilted 23.5 degrees relative to the sun; the tilt causes different amounts of sunlight to reach different regions of the planet.” Video after the break.

While the June solstice generally occurs on the same day every year, the date does change every once in a while. For example, in 2008, the summer solstice occurred on June 20.

[via NationalGeographic]