They say “If winter is here, can spring be far behind?” This year spring commenced on Friday, March 20 in US. Everyone wants to make the most of it, especially after a dreadful winter which meant snow, snow & some more snow. However, the bad news is that the season of flowers and showers is actually getting shorter every year by about 30 seconds to a minute. This is due to astronomical abnormalities, as per a group of researchers.
For example this year, spring officially started in US at 6:45 p.m. EDT on March 20, as per National Weather Service. At that exact moment, which is called the Spring or vernal equinox, the Earth's axis is at a halfway mark, where it points neither toward the sun (as it does on the summer solstice on 21June) nor away from the sun (as it does on the winter solstice 21 December).
But for thousands of years, spring has been slowly but surely losing time in the Northern Hemisphere. This year, summer has the longest duration, with a duration of 93.65 days, followed by spring lasting 92.76 days, autumn covering 89.84 days, and winter which will last 88.99 days. As the years roll on, spring will continue to lose time to summer, and winter will continue losing time to autumn. If this trend continues, & there are no reasons to think otherwise, by the year 3000, the seasonal lengths would have altered in the Northern Hemisphere. So summer would be 93.92 days, spring will be of 91.97 days, autumn will last 90.61 days, and winter will be of 88.74 days.
What is the reason for this change?
The Earth's seasons are caused by the tilt of the Earth on its axis and not by how close or the farther away the earth is to the sun. This tilt of 23.5-degrees, which means that the axis is not straight-up but instead, for six months of the year, the Earth's Northern Hemisphere is tilted slightly towards the sun. Whereas during the next six months, the Southern Hemisphere tilts toward the sun. The main reason spring is getting shorter is that the Earth's axis itself rotates, similar to a spinning top, in a type of conical motion called precession.
Balancing Act of Equinoxes
Spring will end at the summer solstice, and due to precession, the point along the Earth's orbit where the earth reaches the summer solstice will shift ever so slightly. Hence, next year, the earth will reach the point in its orbit of the solstice slightly earlier. Spring will end, and summer will begin, just a wee bit earlier in the year. Thousands of years later, the shift in the time of the spring equinox will become more apparent. For example, spring will be shortest approximately in the year 8680, measuring about 88.5 days, or roughly four days shorter than this year's spring. After that point of time, spring will start lengthening again.
Spring is shorter than summer
At the point of perihelion, the Earth is nearest to the sun, i.e. at a distance of about 91.6 million miles farther away from the sun. When the Earth is farthest from the sun in early July, during aphelion, the distance is close to 94.8 million miles. This phenomenon is peculiar to US as the seasons in US are governed by equinoxes & solstices unlike other countries where seasons are divided by months.