In my area, why doesn't the... | Almanac.com

In my area, why doesn't the...

Print Friendly and PDF
In my area, why doesn’t the vernal equinox (equal night) on March 20 have the same number of hours for day and night? (It was March 17 this year!)
Our astronomer, George Greenstein, had this to say: There are two reasons. First, light rays from the Sun are bent by Earth’s atmosphere. (This is why the Sun appears squashed when it sets.) They are bent in such a way that we are actually able to see the Sun before it rises and after it sets. The second reason is that daytime begins the moment any part of the Sun is over the horizon, and it is not over until the last part of the Sun has set. If the Sun were to shrink to a starlike point and we lived in a world without air, the spring and fall equinoxes would truly have “equal nights.”