The first day of spring in the northern hemisphere in 2018 is 20 March, according to the astronomical cycle.
This date is when day and night are around the same length, each lasting around 12 hours. It usually takes place on 19, 20 or 21 March every year.
In the southern hemisphere, the opposite occurs, as autumn begins at the same time. Spring starts in September south of the equator on the same day autumn starts north of the equator.
read more
How the spring equinox works
An illustration of the spring equinox. Shayanne Gal/Business Insider
An illustration of the spring and fall equinox and the summer and winter solstice. Shayanne Gal/Business Insider
The Earth orbits the sun once every 365 days and 6 hours. Our planet also rotates once per day around a tilted axis.
That tilt is about 23.5 degrees (for now) and bathes different parts of the world with various intensities of light over the course of a year. Meanwhile, the planet’s rotation keeps the heating even, sort of like a 7,917-mile-wide rotisserie chicken made of rock and a little water.
The spring equinox occurs when the sun’s warming rays line up perpendicular to Earth’s axial tilt.
read more
