![]() ![]() Long before conceiving this equality, primitive equatorial cultures noted the day when the Sun rises due east and sets due west, and indeed this happens on the day closest to the astronomically defined event. They are not exactly equal, however, because of the angular size of the Sun, atmospheric refraction, and the rapidly changing duration of the length of day that occurs at most latitudes around the equinoxes. On the day of an equinox, daytime and nighttime are of approximately equal duration all over the planet. The word is derived from the Latin aequinoctium, from aequus (equal) and nox ( genitive noctis) (night). ![]() The instants of the equinoxes are currently defined to be when the apparent geocentric longitude of the Sun is 0° and 180°. In modern times, since the Moon (and to a lesser extent the planets) causes Earth's orbit to vary slightly from a perfect ellipse, the equinox is officially defined by the Sun's more regular ecliptic longitude rather than by its declination. Equivalently, this is the moment when Earth's rotation axis is directly perpendicular to the Sun-Earth line, tilting neither toward nor away from the Sun. More precisely, an equinox is traditionally defined as the time when the plane of Earth's equator passes through the geometric centre of the Sun's disc. This occurs twice each year, around 20 March and 23 September. On the day of the equinox, the Sun appears to rise "due east" and set "due west". Give it a try - and, see below for spring-themed books to read with your child.Equinoxes and solstices on Earth eventĪ solar equinox is a moment in time when the Sun crosses the Earth's equator, which is to say, appears directly above the equator, rather than north or south of the equator. The feat simply takes the right egg, a little practice, and a lot of patience. Standing an egg on its end is something just about anyone can do any day of the year. There is no gravitational change during the equinox that would help an egg balance. The bottom line: This egg-balancing trick is just an old wives' tale. “This is why standing on two feet is easier than standing on only one foot.” ![]() “We stand upright by keeping our own personal centers of gravity within the bounds of our feet on the ground,” says Keller. You would not have time to balance your egg!"Ī balancing act: Is it possible to balance an egg in an upright position? The key is finding an egg with a yolk centered in the shell. “Even were there such a solar influence, it would only work in one place at a time, and that place would be moving at a speed on the surface of the Earth of about 1,000 miles per hour at the equator. The idea that an egg could balance on this day comes from the thought that since the Sun and Moon are equidistant from the earth, the pull of gravity is equalized and therefore an egg is less likely to fall over. The equinox, explained: The spring equinox occurs when the Earth is tilted parallel to its path of motion around the Sun, which makes the length of the day and the night exactly the same. Here, three things to know about the equinox and eggs: Keller, PhD, CEO of Smart Science Education Inc., for his scientific opinion. We wondered … is it really true? So we reached out to Harry E. Each season, this idea seems to pop up on the news, in social media, and in schools. Legend has it that on the spring equinox, you can balance an egg in an upright position thanks to the Earth’s position relative to the sun. ![]()
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