How many hours of daylight are there on the March equinox in Arizona?

Answer 1

The entire earth experiences 12 hours of daylight and 12 hours of darkness on both equinoxes. One equinox, the spring, or vernal equinox, is on March 21st. The other, the autumnal equinox, is on September 21st. Wikipedia, the free encyclopedia, has posted an informative article on the equinox, and a link is provided. Why not wander on over and see what's up?

Answer 2

Assuming you mean the date of the equinox (which often occurs on 21 March, but sometimes on the 20th), the sun is up approximately 12 hours on that day and is set for 12 hours. This is true at the equinox in Chicago or anywhere else in the world (except exactly on the poles). I say "approximately 12 hours" because it is actually slightly more than 12 hrs due to the fact that the sun is 0.5 degrees wide. The center of the sun will be up for 12 hours on that day, but one edge will peek over the horizon a few minutes before, and the opposite edge will not set until a few minutes after the sun's center disappears below the horizon. Typically, the sun is visible for about 12 hours 12 minutes on the equinox. Note that that assumes a zero degree horizon, for instance at sea; hills or mountains will decrease the time you can see the sun.

However, you asked about "daylight" not specifically about the sun being up. That's a vague question because the amount of light preceding sunrise or following sunset is defined in different ways. Even the laws of different states vary on when you should have your headlights on -- some say "at sunset," but others say a specified "xx minutes after sunset."

There are three methods often used to define the amount of light preceding sunrise or following sunset: Civil Twilight, Nautical Twilight, and Astronomical Twilight.

Civil twilight occurs between the time the sun is between zero degrees (just before sunrise or just after sunset) and 6 degrees below the horizon. For 21 March 2010, at Chicago, from the time civil twilight begins prior to sunrise and when it ends following sunset is 13 hrs, 7 min.

Nautical twilight occurs between the time the sun is between 6 degrees below the horizon and 12 degrees below the horizon. For 21 March 2010, at Chicago, from the time nautical twilight begins prior to sunrise and when it ends following sunset is 14 hrs, 13 min.

Astronomical twilight occurs between the time the sun is between 12 degrees below the horizon and 18 degrees below the horizon. For 21 March 2010, at Chicago, from the time astronomical twilight begins prior to sunrise and when it ends following sunset is 15 hrs, 19 min.

Note that their length can vary by a couple of minutes for a specific date from year to year. This is because the sun is not in the exact same place from earth's perspective every March 21st. That's why we have to add a leap day each 4 years.

Answer 3

On the March equinox in Arizona, there are approximately 12 hours of daylight and 12 hours of darkness. This is because the equinox marks the point when the sun is directly above the equator, resulting in equal lengths of day and night across the globe.

Answer 4

12 hours. It's equinox, right?

Answer 5

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