Thursday evening, at 9 p.m. Eastern Time is the formal start of fall, often known as the autumn equinox.
The summer and winter solstices and the autumnal and vernal equinoxes only happen twice a year, on the first day of each season.
According to the National Weather Service, on an equinox, daylight and nighttime are roughly equal since the Earth is not tilted toward or away from the sun.
When this occurs, the sun will be directly overhead at midday in locations near the equator. Because the sun's rays are refracted by the atmosphere, it appears above the horizon when
in reality it is below it, creating a false sense of equality between day and night. There is a maximum tilt of 23.5 degrees toward or away from the sun on the day of the solstice.
The longest day of the year occurs on the summer solstice because the sun is squarely above the Tropic of Cancer in the Northern Hemisphere. Winter has arrived in the Southern Hemisphere,
while winter has arrived in the Northern Hemisphere due to the tilt of the Earth's axis away from the sun. Similarly, the winter solstice in the Northern Hemisphere occurs on the day of the
year with the fewest hours of daylight because of the hemisphere's tilt away from the sun. Summer has arrived in the southern hemisphere as the sun now rises above the Tropic of Capricorn,
summer has arrived in the southern hemisphere. It's true that during an equinox, the days are marginally longer in the northern hemisphere. At the equator, about 12
hours and 7 minutes of daylight is possible. A day at the North Pole, which lies at around 60 degrees north latitude, is about 12 hours and 16 minutes long.