Today in Long Beach is the closest we will come to an even 12 h of "day"/12 h of "night" before the summer solstice. Officially--sunrise @ 0701; sunset @ 1901 but 17 sec short of "dead even."
Sunrise and Sunset time are affected by both the position of the earth in its orbit and the refraction of sunlight through the atmosphere. The sun will appear to be above the horizon in the AM even with it is slightly below the horizon. The same happens at sunset.Today in Long Beach is the closest we will come to an even 12 h of "day"/12 h of "night" before the summer solstice. Officially--sunrise @ 0701; sunset @ 1901 but 17 sec short of "dead even."
Who's Mary?Today is the day. Drink celebrate and be Mary.
Yes but, sunrise is when the top edge of the sun comes above the horizon and sunset is when the bottom edge goes below the horizon and so the "day" is longer than the "night" by twice the amount of time it takes for the disc of the sun to traverse the horizon. That is why your solstice is apparently arriving early.Today in Long Beach is the closest we will come to an even 12 h of "day"/12 h of "night" before the summer solstice. Officially--sunrise @ 0701; sunset @ 1901 but 17 sec short of "dead even."
Today is the day. Drink celebrate and be Mary.
Who's Mary?
According to the table I'm seeing for Long Beach, the sun rises at 090 and sets at 270 degs T, respectively, on March 18 & 19. Thus, neither of the two empirical criteria we've discussed--equal length of day/night and azimuths of the sun at rise/set, which themselves do not coincide with each other, appear NOT to match in time the astronomical definition, which puts it (equinox) on March 20 . How would we know, lacking a calendar?I always look at this and the fall equinox as the time when the sun rises due East and sets due West
First you find a big field. Then you find some big rocks. Put them in a circle and watch the shadows.According to the table I'm seeing for Long Beach, the sun rises at 090 and sets at 270 degs T, respectively, on March 18 & 19. Thus, neither of the two empirical criteria we've discussed--equal length of day/night and azimuths of the sun at rise/set, which themselves do not coincide with each other, appear to match in time the astronomical definition, which puts it (equinox) on March 20 . How would we know, lacking a calendar?
The geometry of what is happening is infinitely complex. Given the wobble in the Earth's rotation (mentioned by Will above), the fact that the orbit around the sun is not an exact number of either solar or sidereal days, (neither of which is constant compared with say an atomic clock) and the non circular nature of the earth's orbit, and the gravity of the moon and other planets and and and - the deeper you go into it the more impossible it becomes for ordinary mortals. I don't know for certain, but I suspect that at a millisecond (or microsecond?) level it is probably actually chaotic (i.e. non repeating) because the influencing factors are so subtle and asynchronous. I need to talk to one of my astrophysicist buddies.According to the table I'm seeing for Long Beach, the sun rises at 090 and sets at 270 degs T, respectively, on March 18 & 19. Thus, neither of the two empirical criteria we've discussed--equal length of day/night and azimuths of the sun at rise/set, which themselves do not coincide with each other, appear to match in time the astronomical definition, which puts it (equinox) on March 20 . How would we know, lacking a calendar?