Spring officially started last Friday evening, even if a good majority of folks in the north were still seeing snow on the ground and ice on the roads. And while these last legs of chilly weather may seem to indicate that spring has been pushed back, the reality is that the season is actually shortening, with summer expected to come earlier than ever before this year.

That's at least according to a little-known rule about seasons in the Northern Hemisphere. Astronomers know that each year, without fail, the moderate seasons (spring and fall) have been losing time to the seasons that follow (summer and winter, respectively).

But before we go into exactly why this occurs, we should fist discuss the 'what' - that is, what exactly are seasons?

We all should know (sadly, not everyone does) that a full year ends when the Earth completes a full orbit around the Sun. Interestingly, this orbit is not a perfect circle, and at various times in the year, the Earth is closer or further from the massive, fiery ball that hosts it. And just like drawing closer or further from a campfire, this affects how the Sun warms our planet.

"During the first week in January, the Earth is about 1.6 million miles closer to the Sun. This is referred to as the perihelion," the NOAA reports. "The aphelion, or the point at which the Earth is about 1.6 million miles farther away from the Sun, occurs during the first week in July."

Now would be a good time to start scratching your head. 'Now wait a minute! Isn't January colder than July?!'

Well yes, but how a net warming of the planet affects one part of the Earth determines seasonal weather patterns, not the seasons themselves. In the same way, this is why experts have been saying that a warming climate due to climate change could actually mean more snow and extreme weather inbound for some parts of the Northern Hemisphere.

What actually determines seasons, then, is the tilt of the Earth as it goes though its orbit.

"Seasons are caused by the fact that the Earth is tilted on its axis by 23.5°. The tilt's orientation with respect to space does not change during the year," added the NOAA. "Thus, the Northern Hemisphere is tilted toward the Sun in June and away from the Sun in December." (Scroll to read on...)

What causes this shortening of the moderate seasons then, is something called precession (as part of the great Milankovitch Cycle theory).

This phenomenon can best be described as a wobble of the Earth's axis, temporarily changing that all-important axis tilt by the littlest bit each year. Because of this 'wobbling top' mechanism, where the Earth's orbit is when the summer solstice is reached shifts slightly on an annual basis. This shift is only by a few dozen seconds, but over thousands and thousands of years, that can make for some big changes. (Scroll to read on...)

[Credit: NASA]

Larry Gerstman, an amateur astronomer in New York, even recently explained to Live Science's Laura Geggel that the general consensus holds that by the year 8680, spring will be four days shorter than it is now, lasing for a mere 88.5 days. This year, he added, spring and summer will still be the longest seasons, with summer lasting an estimated 93.65 days. Next year, it will be 30 seconds to a minute longer.

So rejoice! Winter may have taken its sweet time ending this year, but you have a longer (albeit, barely notably so) summer ahead of you!

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