Autumnal Equinox

Autumn has officially arrived in the northern hemisphere leading to longer nights and colder days.

19:08 24 September 2015

Autumn has officially arrived in the northern hemisphere as marked by the autumnal equinox when the Sun passes directly over the Earth’s equator. This is measured by a celestial event that meteorologists use to indicate the end of summer.

 

The equinox takes place twice a year on or around May 23 and September 23 and occurs due to the tilt of the Earth in relation to the sun, causing the seasons.

 

During summer, the Northern hemisphere is titled towards the sun and in the winter, the Southern hemisphere gets the majority of the light.

 

“The Earth’s orbit is [only] about three percent out of round,” explains Jay Holberg, a senior research scientist at the lunar and planetary lab at the University of Arizona.

 

“So in the northern winter—in December—the sun is actually closest to the Earth by a small amount, and in the summer it’s actually farther away,” he told National Geographic.

 

Matthew Holman, an astrophysicist at Harvard University said: “The equinox is defined as the time of an event. It’s really not when the day and the night are of equal length,although that’s what we think of - it’s really that moment is when the sun is on the equator at local noon."