|
|
|
Dodge City Daily Globe - Dodge City, KS
  • Looking Up: Sun, geese and snow birds

    • email print
      Comment
  • Geese have been flying north for some time. Soon our snow bird population wintering in Florida and other warm places will be driving their RVs (some use cars) toward the North Star. At last, the sun is making its trek north, and we are glad for the added sunlight and warming temperatures.
    Spring officially arrived on March 20. That's when the sun’s position crossed the equator, standing directly overhead at noon on the equatorial line running across Brazil and many other countries. Every day at noon, the sun shines a little bit higher till the start of summer, when it stands overhead from the northern edge of the tropics, the latitude known as the "Tropic of [constellation] Cancer."
    (Its southern counterpart, you may recall, is the Tropic of Capricorn, the latitude where the sun stands directly overhead at noon, on the first day of autumn in the northern hemisphere.)
    On March 20, if you live "Down Under," the sun is moving away and autumn has just begun. Far southerners see the sun continue to dip, until its low point in June, the high point as seen from the Northern Hemisphere.
    Alas, for night sky enthusiasts, a trade-off of longer days mean shorter nights! On top of that, for most of us, daylight saving time is in effect and puts off the stars another hour. By late June, the sky is not fully dark in the mid-northern latitudes until close to 11 p.m. Still, we make the best of it, and the shorter window of stars becomes all the more precious. At least later at night, there is usually less light pollution (more people have turned off the lights) and less air pollution (the day’s dust is settling down).
    As every schoolchild learns (we hope), changing of the seasons occurs because the Earth is tipped to one side. All the planets are tipped, by varrying amounts; Jupiter, however, is nearly straight up and down, and Uranus is tipped almost completely over! By "tipped" we mean the imaginary line between the North and South pole, through the Earth’s center - which we know as the axis of rotation - is less than perpendicular to our orbital plane.
    We can be very grateful for this arrangement, which allows life as we know it to survive around the globe. If the planet were straightened, a large area of the far north and south, and the tropical area, would become either too extreme in temperature for most life.
    The Earth is tipped over 23 degrees, 26 minutes, 21 seconds.
    Because most of the planets all orbit together nearly on one plane, they travel a narrow band around the sky - the ecliptic. The moon follows the same band. The very center is where the sun travels. The Earth’s equator may be imagined projected onto the sky, where it is referred to as the celestial equator. The ecliptic, as seen on the sky, is off-set from the celestial equator, and intersects it at two points. Guess what we call them! These are the points of the first day of spring (the "vernal equinox") and the first day of autumn (the autumnal equinox).
    Page 2 of 2 - Again, if the Earth were straight up and down with no tip (you should always tip, by the way - at least 15 percent), the ecliptic line would follow the celestial equator exactly.
    If you don’t care for the first day in spring occurring in March, just wait! This will be changing, and it has nothing to do with the federal government. The Earth’s axis has a very slow wobble. I mean very slow. Approximately every 26,000 years, the axis moves in a full circle. As it slowly moves away from our North Star and picks different stars to receive that honor, the celestial equator shifts as well. Through the millennia, where the ecliptic intersects that line changes, giving new dates for both equinoxes! As another blow to the pseudo-science of astrology, the constellation where the sun is found during an equinox eventually switches. Currently the sun shines in the constellation Pisces at the springtime equinox; during the Civil War, in 1865, the springtime equinox moved from the constellation Taurus into the constellation Aries. In the year 2597, the equinox occurs with the sun shining in front of the Aquarius constellation. All this shifting means that eventually, star groups such as the Southern Cross, will become visible in mid-northern latitudes. Tonight you need to be in at least mid-Florida to barely see the Southern Cross on the horizon.
    Your comments, questions and observing reports may be sent to news@neagle.com.
    Last-quarter moon is on March 23.
    Keep looking up!

        calendar