Solstice vs. Equinox Defined: The relationship between daylight and seasons

Science

ROCHESTER, N.Y. (WROC) — Upstate New York, along with much of the northern half of the country, is experiencing a change of seasons. Dive into the astronomical reasons for seasons, which is the earth’s path as it tilts toward and away from the sun.

The distance between the planet and the sun has no significant effect on our climate. It’s actually based on the tilt of earth’s axis. During the summer, our hemisphere tilts us farther away from the sun than we are in the winter.

As the earth revolves around the sun, the shifting tilt affects everything from the amount of daylight to temperatures. Our earth makes one full revolution, or trip around the sun, in roughly 365 days. To be exact, it actually takes the earth 365.24 days to make its full trip, which is why we have a leap year that accounts for the extra day we accumulate every four years.

Image courtesy: weather.gov/cle/seasons

Solstice (Summer and Winter)

When the earth is tilted at its maximum towards the sun, it’s called the summer solstice. This is the day where the sun is at its highest in the sky, and we receive the longest amount of day with the shortest amount of night. The winter solstice is the day where we receive the shortest amount of day and the longest duration of night; the sun being at its lowest in the sky.

At the summer solstice, our hemisphere is angled toward the sun. At the winter solstice, we’re angled away.

Equinox (Vernal and Autumnal)

Since this tilt towards and away from the sun happens very gradually over the course of the entire year, there must be two points during that time period (between when the earth is tilted away and towards the sun) where the earth’s tilt is aligned in such a way that we receive equal parts day and night; a full 12 hours each.

This occurs at an equinox, twice a year, at the start of fall and spring. “Equinox” comes from the Latin “aequus,” meaning equal, and “box,” meaning night. At noon on an equinox, the sun is supposed to be directly overhead, providing us with equal parts day and night in a 24-hour period.

The time of day is measured by when the first bit of light from the sun appears and disappears. Since the atmosphere refracts light, the sun’s top crescent is technically visible a few minutes before sunrise and after sunset. This means that the day and night split of 12 hours in spring happens a few days before the equinox, and in the fall, a few days after.

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