Bet you didn’t know that Spring is coming sooner than most everyone expected. Yup. It’ll be here Sunday, not Monday. Space.com does a great job explaining this:
- A year is not an even number of days and neither are the seasons. To try and achieve a value as close as possible to the exact length of the year, our Gregorian Calendar was constructed to give a close approximation to the tropical year which is the actual length of time it takes for the Earth to complete one orbit around the Sun. It eliminates leap days in century years not evenly divisible by 400, such 1700, 1800, and 2100, and millennium years that are divisible by 4,000, such as 8000 and 12000.
- Another reason is that the Earth’s elliptical orbit is changing its orientation relative to the Sun (it skews), which causes the Earth’s axis to constantly point in a different direction, called precession. Since the seasons are defined as beginning at strict 90-degree intervals, these positional changes affect the time Earth reaches each 90-degree location in its orbit around the Sun.
- The pull of gravity from the other planets also affects the location of the Earth in its orbit.
Something else that is cool that the seasons are changing:
The current seasonal lengths for the Northern Hemisphere are:
Winter 88.994 days Spring 92.758 days Summer 93.651 days Fall 89.942 days
Now this is where it gets cool:
As you can see, the warm seasons, spring and summer, combined are 7.573 days longer than the colder seasons, fall and winter (good news for warm weather admirers).
However, spring is currently being reduced by approximately one minute per year and winter by about one-half minute per year. Summer is gaining the minute lost from spring, and autumn is gaining the half-minute lost from winter. Winter is the shortest astronomical season, and with its seasonal duration continuing to decrease, it is expected to attain its minimum value – 88.71 days – by about the year 3500.
Pretty dang cool. Wonder how many people have considered this in the global warming debate?