Tuesday, March 3, 2015

Equinox, and eggs-istentialism

Despite "equinox," days are longer than nights ... and about that egg.

Equinox, and eggs-istentialism

It has nothing to do with the amazing warmth we've been experiencing, but the days now are noticeably longer than the nights.

Even though "equinox" is derived from the Latin for "equal night," daylight on this first day of spring will last for 12 hours and 10 minutes.

So why isn't this a straight 12-and-12 day/night relationship on the day that the center of the sun beams directly over the middle of the world?

The imbalance has something to do with optics and the Earth's atmosphere.

Technically, sunrise is defined as the moment when the sun's disk first becomes visible on the horizon. Conversely, sunset is the moment when the sinking edge of that disk disappears below the horizon.

But Earth's atmosphere bends the sun's rays in such a way that the sun appears higher in the sky than it would if we had no atmopshere.

Because of this effect, the sun is visible several minutes before its actualy arrival on the horizon, and remains visible for a period a period after it disappears below the horizon.

That would explain the extra minutes of daylight on equinox day. You'll find a tidy discussion of all this at this site.

As for the egg, yes could stand it on end on the equinox, and on Easter, Christmas, the solstice or Labor Day.

You could stand an egg on end any day of the year if you have the right surface and the patience.

Meanwhile, we will continue to enjoy days around here that are suited to a time when the sun sets after 8 p.m.



Tony Wood Inquirer Weather Columnist
About this blog

Everyone talks about the weather, and here we write about it.

When we’re around and conditions warrant, we’ll keep you updated about what’s coming, but we will do our best always to discuss weather and climate developments in context and remind you that nothing in the atmosphere happens in a vacuum.

Tony Wood has been writing about the atmosphere for The Inquirer for 26 years.

Reach Tony at twood@phillynews.com.

Tony Wood Inquirer Weather Columnist
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