Happy Vernal Equinox!

Imagine a world where night and day are the same length, and where the sun rises from the same place and sets in the same place in the sky... every day.

Well, some day I would like to travel there perhaps, but that place is most definitely not Earth! I have no idea how it happened, but our Earth rotates at a skewed angle relative to it's orbit around the sun - 23.5 degrees tilted, as it happens.

But today (or yesterday, depending on your concept of time and what time zone you live in), we get a sample of that world. What does this mean for us? Well, for long-time readers of this blog, write down the answer now, and compare with the rest of this post - this is a quiz. Otherwise, read on and remember - there will be a quiz next year.

Here are the special things for today (and also on September 21st):

• The "equi" and "nox" part - everywhere on earth today (unless you are at the exact poles, in which case you are probably quite cold at the moment) has 12 hours of daylight and 12 hours of night, at least theoretically (we will ignore diffraction for now). No long summers or short winters for Russia - everything is the same, everywhere. And, since most roads run exactly east west, if you are driving at the crack of dawn or dusk, you will have the sun exactly in your eyes or rear-view mirror. (I have to check to see if the car accident rate statistically goes up this time of year).
• Unlike most of the year, the sun actually rises in the (true) east, and sets in the (true) west. From now on, until June 21, it will start to rise more and more in the north, then start moving back until Sept 21. Actually, if you get technical it is a bit more complicated. If you want a good explanation, go to http://www.analemma.com and click the "other phenoma" link.
• At its highest during the day, the sun's elevation (angle above the horizon) will correspond to 90 degrees minus the latitude where you live at. For us in Rochester, that is 47 degrees. For those in, say St. Petersburg, it is 30 degrees above the horizon. I know it seems higher, but go measure it - that is the highest it will get today. (To see the highest it will EVER get in the peak of summer, add 23.5 degrees - got it?).
• Lunar and solar eclipses strongly cluster around the equinoxes. To understand this you really need to get out an orange, paint an equator around it, and imagine a moon orbiting while it (tilted, remember) orbits the sun (a light source). Read about it - this is the stuff everyone needs to know! :-)

There will be a quiz, so study hard!