Vernal Equinox Signals Equal Day and Night Times

Mark your calendar, the next March Equinox (Vernal Equinox) will be on the 21st of March 2018, Wednesday at 12:15 MN, Philippine Time. March equinox also signifies the moment the Sun crosses the Celestial equator – the imaginary line in the sky above the Earth’s equator – from South to North. There are no specific dates in a year when this occurs. It could occur on the 19th, 20th or 21st every year according to Timeanddate.com.

By definition, the word equinox was derived from Latin words aequi (equal) and nox (night), literally translates to equal night. However, it does not necessarily mean that equinoxes have exactly 12 hours of daylight and 12 hours of nighttime. (Time and Date AS, n.d.)

Fig. 1 – Different Equinoxes and Solstices result to changes in seasons across the hemispheres. Image courtesy: WeatherPhilippines

Fig. 1 – Different Equinoxes and Solstices result to changes in seasons across the hemispheres. Image courtesy: WeatherPhilippines

Equator crossing

 Across human history, there are a handful of festivities celebrated by many cultures around the globe which mark the changes in seasons. Nothing is more exciting than that of Springtime which coincides with the Sun’s annual alignment to the equator (See Fig. 2.0).

Little has been known about this phenomenon until the coming of the age of satellites that are put into orbit by man. Man’s fascination of exploration and the insatiable desire to better understand his environment beyond Earth was made possible through innovative ways and advancement in research and technology. This, coupled with ingenuity and seemingly endless quest for knowledge inadvertently unraveled new clues and discoveries of travel well into deep space.

“When the Earth moves around the Sun it actually spins at a tilt which means that most of the year the Northern and Southern Hemispheres are not equally illuminated by sunlight. But during Spring and Fall Equinox, both hemispheres are equally illuminated giving us the astronomical beginnings of Spring,” according to NASA’s Dr. C. Alex Young, a scientist of Heliophysics Science Division at NASA’s Goddard Space Flight Center.

Fig. 2 - The view at the moment about 22,000 miles into space, would be similar to what you see here — two nearly equal slices cut straight down the middle, one light, one dark. Image courtesy: NASA and Eumetsat

Fig. 2 – The view at the moment about 22,000 miles into space, would be similar to what you see here — two nearly equal slices cut straight down the middle, one light, one dark. Image courtesy: NASA and Eumetsat

The spring equinox is a point in Earth’s orbit where the sun shines directly above the equator, creating nearly equal periods of daytime and nighttime across the globe.

Only on the equinoxes do we get that exactly straight terminator,” said Greg Redfern, a solar system ambassador at NASA’s Jet Propulsion Laboratory, referring to the line separating daylight from the darkness of night.

“That line is continually shifting because the Earth is tilted 23.5 degrees on its axis. Without this tilt, we’d always have the straight-up-and-down terminator and we wouldn’t have seasons,” he added.

Time of plentiful warmth

Since the Philippines sits in the Northern Hemisphere, the sunrise becomes earlier and nightfall comes later. It is also the time when plants thrive faster, while the winds grow calmer and the temperature starts to warm up. This signifies the transition from the cool dry season to the much-awaited hot dry months through later June. Then, the country will experience longer days and shorter nights.

In these regions, the vernal equinox signals the start of the hot dry season, which many travelers and vacation-goers look forward to. For many, this is the best time to travel to a popular beach, go camping, or visit water activities locations in the Philippines.

Now that is something to keep in mind when scheduling your out of town trips so you can enjoy this season to the fullest. Download the WeatherPhilippines mobile application and weather-check the areas before visiting your favorite destination. It pays to stay ahead of the weather by being #WeatherWiser!


By: Adonis S. Manzan

Reference:

https://svs.gsfc.nasa.gov/12535

https://www.nytimes.com/2016/03/22/science/what-spring-looks-like-from-space.html?smid=spacecal

https://www.timeanddate.com/calendar/march-equinox.html

©2019 WeatherPhilippines Foundation

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