Happy first day of autumn -- one of my personal favorite days of the year, not only because fall is my favorite season, but Sept. 22 is the last day of a record high of 90 or hotter in Seattle, meaning I can probably safely put away the air conditioner and reclaim a corner of the room.
But with the autumnal equinox comes the usual puzzling questions we get about this day where eggs can stand up on end and we are supposed to get equal daylight and darkness...
Q: OK, smarty pants, you say it's supposed to be 12 hours of daylight today, but your own table on your own fancy web site says sunrise is at 6:56 a.m. and sunset is 7:07 p.m. That's 12 hours and 13 minutes. What's with the extra 13 minutes?
A: It's due to the fact that when we see the sun set, it's already set a few minutes earlier!
The Earth's atmosphere bends the sun's light a little when the sun is low on the horizon. Thus, when we see the sun just going down on the horizon, it had actually set a few minutes earlier, but with the bending of the light, the sun still appears on the horizon.
The U.S. Naval Observatory takes this into account when calculating sunrise/sunset times, so that's where the few minutes' discrepancy comes in. You can read more at USAToday.com. They even have a fancy graphic.
If you want to find out exactly when the seasons begin -- check out this handy chart that goes through 2020. Only trick -- these times are the old Grenwich time, or "UTC" time.
Subtract 8 hours for the start of winter, and 7 hours for the start of spring, summer, and fall as we are on PDT then. (Note sometimes that means the seasons begin on a different day in Seattle than, say, New York or London if our season begins just before midnight.)
Q: What about the South Pole? They have just one sunrise a year, right?
A: Yes. In fact, it's just one, 24-hour sunrise. Check out this video from the ICE Neutrino Lab at the South Pole. A friend of a frequent e-mailer took this time-lapse video of Monday's equinox sunrise as spring begins there.
It takes a full day for the sun to rise completely. The video shows a few hours as it moves along the horizon and rises. At the pole it rises a little before the official equinox because they are 10,000ft above sea level. It will be up until March.
There's some old wives tale about how on the first day of spring and autumn, you can stand an egg up on its end. You can search the Internet and find photos of such accomplishments.
(Photo courtesy Phil Plait's "Bad Astronomy" Web site. By the way, this was taken in an October.)
The legend appears to stem from some sort of "seasonal gravity." Unlike Dec. 21 when the Earth's tilt has us pointed away from the sun, and June 21 is when we're tilted the most toward the sun, the equinox dates are when we're exactly in between, and the Earth's tilt is at a 90 degree angle with respect to the sun's light.
Some felt that meant the Earth's tilt is zero then, and so with the Earth pointing straight up, that eggs will stand up and not be pulled over by the tilt.
But it's all gibberish. Actually, the Earth's tilt doesn't move at all -- at least not noticeably. The seasons occur because of Earth's tilt relative to the sun as we orbit around, but our planet spins on the same axis year 'round, so even if the Earth's tilt affected gravity, nothing would change between each day. (Now, over thousands of years, we do wobble a bit, but that's another story)
No, what really matters is nothing more than making sure you have a flat surface and an egg that has formed evenly. So, the long and short of it is, you can stand the right egg up on its side no matter what day of the year it is!
But feel free to go try and stand an egg up now -- just be sure to clean up the mess if it rolls off the table :) And if you do get a good photo of the feat, we'd love it if you submit it to our YouNews site.
(Thanks to Phil Plait's "Bad Astronomy" Web site for information on this topic. It's really a great site!)
Q: What's the best way to keep my leaves pile from blowing around?
A: Wait to collect leaves until we are safely out of the windy season... like mid-May :)
Have a happy autumn!