Spring Equinox

Although there’s nothing official about it, it’s traditional to say the March or vernal equinox signals the beginning of spring in the Northern Hemisphere and autumn in the Southern Hemisphere. Like all equinoxes, this one will provide a hallmark for the sun’s motion in our sky, marking the passage of the sun across the celestial equator, going from south to north. The coming equinox will fall on March 20, 2020, at 03:50 UTC. That’s March 19 at 10:50 p.m. Central Daylight Time for us in the central U.S

In the Northern Hemisphere now, the March equinox will bring earlier sunrises, later sunsets, softer winds, sprouting plants. Meanwhile, you’ll find the opposite season – later sunrises, earlier sunset, chillier winds, dry and falling leaves – south of the equator.

The equinoxes and solstices are caused by Earth’s tilt on its axis and ceaseless motion in orbit. You can think of an equinox as happening on the imaginary dome of our sky.

The Earth-centered view is that the celestial equator is a great circle dividing Earth’s sky into northern and southern hemispheres. The celestial equator wraps the sky directly above Earth’s equator. At the equinox, the sun crosses the celestial equator, to enter the sky’s Northern Hemisphere.

The Earth-in-space view is that, because Earth doesn’t orbit upright, but is instead tilted on its axis by 23 1/2 degrees, Earth’s northern and southern hemispheres trade places in receiving the sun’s light and warmth most directly, as Earth orbits the sun. We have an equinox twice a year – spring and fall – when the tilt of the Earth’s axis and Earth’s orbit around the sun combine in such a way that the axis is inclined neither away from nor toward the sun.

At the equinox, Earth’s two hemispheres are receiving the sun’s rays equally. Night and day are often said to be equal in length. In fact, the word equinox comes from the Latin aequus (equal) and nox (night). For our ancestors, whose timekeeping was less precise than ours, they likely did seem equal. But we today know it’s not exactly so.

Here’s another equinox phenomenon. You might hear that the sun rises due east and sets due west at the equinox. True? Yes, virtually so. And that’s the case no matter where you live on Earth. At the equinoxes, the sun appears overhead at noon as seen from Earth’s equator, as the illustration above shows. This illustration shows the sun’s location on the celestial equator, every hour, on the day of the equinox.

No matter where you are on Earth – except at the Earth’s North and South Poles – you have a due east and due west point on your horizon. That point marks the intersection of your horizon with the celestial equator – the imaginary line above the true equator of the Earth.

That’s why the sun pretty much rises due east and sets due west for all of us. The sun is on the celestial equator, and the celestial equator intersects all of our horizons at points due east and due west.

All info from: https://earthsky.org/astronomy-essentials/everything-you-need-to-know-vernal-or-spring-equinox