Spring Is Here! Vernal Equinox Has Just Started; What Is the Astronomy Behind This Seasonal Change?

Scarves, hats, and winter coats can now be stored away because spring is here!

'Astronomical' Spring Is Here!

As per the Daily Mail, the Spring Equinox has taken place, which marks the beginning of astronomical spring. At exactly 15:33 GMT on March 20, the sun directly passed over the equator. This makes the duration of day and night nearly equal across almost the entire earth.

NASA notes that the March equinox, which is also referred to as the vernal equinox, astronomically marks the start of spring season across the Northern Hemisphere. Seasons get reversed in the Southern Hemisphere, where autumn takes place.

Spring equinox usually takes place on March 19, 20, or 21. According to the New York Post, equinoxes generally take place in March and September each year. These events mark the start of autumn and spring. When an equinox takes place, both night and day become equal.

There is, however, a twist to this March equinoxes, as actual day and night duration is not exactly equal. Space reports that, during the dates of equinoxes in March and September, daylight length is longer compared to darkness. They differ by several minutes.

For those from the north, the Spring Equinox will lead to later sunsets and earlier sunrises. In contrast, those from the south of the equator may experience earlier sunsets and later sunrises.

Earth Has Two Types of Seasons

While individuals are generally familiar with the four seasons of earth, many may not know that the earth actually has two types of seasons: meteorological seasons and astronomical seasons.

According to the Daily Mail, meteorological seasons follow monthly calendar changes. They are based on the annual cycle of temperature. The National Geographic notes that, basically, for this type of season, the calendar is chunked into four different seasons that last for three months. For instance, meteorological spring starts on March 1 and lasts until May 31.

Astronomical seasons, on the other hand, are based on the earth's position during its orbit and on the tilt of the planet's axis. These seasons are based on the occurrences of equinoxes that take place every six months. The National Geographic reports that, as the new season moves, the position of the sun changes as well. Depending on which hemisphere one lives in, days may end up darker or lighter until solstice arrives.

Solstices mark the year's brightest and darkest days. They are also based on the tilt of the earth and mark the start of astronomical winter and summer.

Having two types of seasons means that each season starts twice. Generally, meteorological seasons are simpler compared to astronomical ones.

However, aside from these, people tend to unknowingly define seasons phenologically. The Daily Mail notes that individuals may refer to life indicators, such as the blossoming of particular trees or the growth of certain plant species.

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