Equinox vs. Solstice: Why We Have Seasons

By leah jones

The equinox is an astronomical event that occurs twice a year. In the northern hemisphere, the Vernal (or spring) Equinox falls between Mar. 20-22 and the Autumnal (or Fall) Equinox falls between Sept. 21-23.

What Is the Equinox?

The Sun is positioned directly above the equator on the Vernal and Autumnal Equinoxes, resulting in nearly equal daylight and nighttime hours across the planet.

What Is the Equinox?

The Vernal Equinox marks the beginning of spring in the hemisphere experiencing it. It differs from the Autumnal Equinox as the Sun’s path is moving north of the equator.

Vernal Equinox (Spring Equinox)

The Autumnal Equinox marks the beginning of autumn in the hemisphere experiencing it. It differs from the Vernal Equinox as the Sun’s path is moving south of the equator.

Autumnal Equinox (Fall Equinox)

We have seasons because the earth is titled at 23.5 degrees on its axis as it orbits the Sun. This causes the northern and southern hemispheres to be tilted toward or away from the Sun at different times of the year.

The Role of the Earth’s Axis

Earth’s tilt on its axis also makes it so the seasons are opposite in the northern and southern hemispheres.

The Role of the Earth’s Axis

When one hemisphere is tilted toward the Sun, that hemisphere is in summer, while the other is tilted away from the Sun, experiencing winter.

The Role of the Earth’s Axis

Additionally, Earth’s tilt on its axis determines how much sunlight the planet receives throughout the year. That is when the equinoxes and solstices come in.

The Role of the Earth’s Axis

The equinox and solstice are very different. The solstice is an astronomical event that happens twice a year, marking when the hemispheres are tilted most directly toward or away from the Sun.

What Is the Solstice?

The result of the solstice is either the longest day of the year in summer, or the shortest day of the year in winter solstice. It also results in the most unequal daylight and nighttime hours across the planet.

What Is the Solstice?

The summer solstice occurs between June 20-22 in the northern hemisphere and is the official start of summer. It marks the longest day/shortest night of the year and when the Sun’s path is furthest north of the equator.

Summer Solstice

The winter solstice occurs between Dec. 20-22 in the northern hemisphere and is the official start of winter. It marks the shortest day/longest night of the year and when the Sun’s path is furthest south of the equator.

Winter Solstice

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