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Vernal Equinox: Beginning of Spring

Blooming daffodils, a songbird at dawn and the warmth of the afternoon sun – spring is coming!

Vernal Equinox, also called “March Equinox” or “Spring Equinox,” marks the beginning of spring in the Northern Hemisphere. The word equinox is derived from the Latin words aequus (equal) and nox (night).

During equinox, the sun crosses from the southern hemisphere to the northern hemisphere. At some point, the sun shines directly over the earth’s equator, providing each of the earth’s hemispheres with almost the same amount of sunlight. A nearly equal amount of daylight and darkness at all latitudes is a result of the tilting of the Earth’s axis neither toward nor away from the sun.

Equinox means the day and night will be in approximately equal length. The National Oceanic and Atmospheric Administration (NOAA) says the “nearly” equal hours of day and night are due to the refraction of sunlight or bending of the light’s rays, causing the sun to appear above the horizon when the actual position of the sun is below it.

This event takes place at the same moment across the world. In the Philippines, the Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA) said it will happen on March 21 at 6:45 AM in Philippine Standard Time (PST). It occurs when the motion of the sun allows it to pass the first point of Aries, an imaginary location in the sky.

Since we only have two official seasons here, the vernal equinox does not herald spring, but will mark the start of longer number of hours during the day. Because it takes the sun longer to rise and set, days become a little longer at the higher latitudes. According to PAGASA Weather Forecaster Gener Quitlong, higher temperatures will begin as we get longer exposure from sun rays.

Spring as seen from space

Fireball Season

Bill Cooke of the National Aeronautics and Space Administration (NASA) said the rate of bright meteors or fireballs increases during the weeks around the vernal equinox. In spring, fireballs are more abundant– the nightly rate reaching 10% to 30% higher than usual. Fireballs are meteors brighter than the planet Venus. Studies have shown that aside from the fireballs, meteorites are also common in spring.

Photo: http://apod.nasa.gov/
Photo Credit: http://apod.nasa.gov/

Aurora Season

Scientists found out that the weeks around the vernal equinox are prone to Northern Lights. The bright dancing lights of the aurora are caused by the collision between electrically charged particles from the sun that enter the earth’s atmosphere. NASA has deployed a fleet of five spacecraft to study auroras and was named THEMIS (short for “Time History of Events and Macroscale Interactions during Substorms”).

It was discovered that magnetic connections between the Sun and Earth are favorable during springtime. During equinox, the magnetic field of the Earth is best oriented for “connecting” with the sun, giving way for solar wind energy to flow in and spark Northern Lights.

Photo Credit: Jeffrey R. Hapeman of Lac du Flambeau, Wis.
Photo Credit: Jeffrey R. Hapeman of Lac du Flambeau, Wis.