![]() But instead day starts a little earlier and ends a little later, making it longer than night. ![]() If we measured the day starting and ending when the sun’s center breached the horizon, we’d be fine day and night would be equally parsed. Daytime starts when the topmost bit of the sun rises above the horizon, but it doesn’t end until the topmost bit sinks below the horizon. But it turns out they’re only mostly equal because of a couple of pernicious physical facts.įirst among them is the fact that we measure the length of daytime in a weird way. The trouble’s right in the name: “equinox” means “equal night”, implying that day and night are each 12 hours long. That’s a common misconception and an understandable one. In some ways, defining what the equinox isn’t is easier than describing what it is.įor example, it’s not when the day and night have equal lengths. But also, just reverse the seasons and add six months to the dates as you read them, and you’ll be fine.) There are many more interesting things to see. If you live below the equator, first, congratulations southern skies are far better than northern ones. For the duration of this article, I’ll show my own bias by using the northern names and dates. (Seasons, months and names get a little confusing in this topic because Earth is a tilted ball, and the Southern Hemisphere’s seasons are the opposite of the Northern Hemisphere’s ones. Friday PDT), the sun will be directly over Earth’s equator, which is how astronomers define the equinox. Happy September equinox! Or, as we say north of the equator, happy autumnal equinox!
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