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longing for more daylight?

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  • longing for more daylight?

    The shortest day of the year may not be until the winter solstice, but did you know that the earliest sunset of this year is on December 10th? Yes, you'll have more sunlight for your commute home from work starting on Monday!! On the flip side, the latest sunrise won't occur until January 3rd.
    Scooting here and there
    Through the woods and up the peaks
    Random Scoots awaits (DP)


    Eat, sleep, hike, repeat.

    It doesn't have to be viewtiful to be beautiful. (NL)

    "Pushing the limits of easy."

  • #2
    Yea, I could use some more.
    The season of darkness is full-tilt now for sure,,,,,and it sux.

    A very cool event tomorrow, early morning. A very tight grouping of MArs, Jupiter & Mercury in the SE at dawn. Pretty rare.

    We also saw the northern lites last nite, very faintly and moving rapidly.
    Walk Softly

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    • #3
      Originally posted by randomscooter View Post
      The shortest day of the year may not be until the winter solstice, but did you know that the earliest sunset of this year is on December 10th?
      How does this work, exactly? I don't doubt that it's true, I'm just curious as to the mechanics of it.
      46/46, 12/48, 58/115
      46-R #6866

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      • #4
        Originally posted by AdkWalrus View Post
        How does this work, exactly? I don't doubt that it's true, I'm just curious as to the mechanics of it.
        That's a darned good question. All I can say is that many years ago my mom mentioned to me that she always thought the days were getting longer even before the winter solstice, so I looked at a sunrise/sunset chart and discovered that she was half right - the end of the day that she noticed the most, sunset, was indeed getting longer before the winter solstice.

        If you go to sunrisesunset.com you can create a sunrise/sunset chart for any latitude/longitude. By plugging in various combinations of lat/long you'll find that the phenomenon is a function of latitude. At the Arctic Circle the latest sunrise and earliest sunset are both on the same day, the winter solstice. As you go south from there the latest sunrise occurs more after the solstice and the earliest sunset occurs more before the solstice.
        Last edited by randomscooter; 12-10-2006, 02:30 AM.
        Scooting here and there
        Through the woods and up the peaks
        Random Scoots awaits (DP)


        Eat, sleep, hike, repeat.

        It doesn't have to be viewtiful to be beautiful. (NL)

        "Pushing the limits of easy."

        Comment


        • #5
          And if you don't have your exact latitude/longitude you can just google sunset times and choose the first link. Pick the city closest to you and a calendar will come up with the sunrise/ sunset on each day. Under each month you can keep picking future months. Had a fun time paying with June also.
          Life isn't about waiting for the storm to pass.
          It's about learning to dance in the rain.

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          • #6
            Originally posted by AdkWalrus View Post
            How does this work, exactly? I don't doubt that it's true, I'm just curious as to the mechanics of it.
            The earth's orbit is not exactly circular, darn close, but not quite. The shape is an ellipse. Of course it is the tilt of the earth's spin axis that causes our seasonal changes and daily shortening/lengthening change in sunrise/sunset times. You would get the expected answer if our orbit was circular. The earth is in fact slightly closer to the sun (and travelling faster along the orbital path) in the northern hemisphere winter than we are in summer.

            Our shortest day of total daylight (always the first day of winter, the solstice) does not correspond to the date of our closest approach to the sun, which is by coincindence just a couple of weeks later. It's somewhat complicated math, but if you work out calculations of the spinning earth traveling along the ellipse, along with the direction in space of the earth's axis tilt and the time the sun appears on the horizon, then you get a slight offset from intuitive earliest/latest sunrise/sunset times.
            Last edited by Nessmuk; 12-10-2006, 10:37 AM.
            "Leave the beaten track behind occasionally and dive into the woods. Every time you do you will be certain to find something you have never seen before." - Alexander Graham Bell

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            • #7
              Originally posted by Nessmuk View Post
              The earth's orbit is not exactly circular, darn close, but not quite. The shape is an ellipse. Of course it is the tilt of the earth's spin axis that causes our seasonal changes and daily shortening/lengthening change in sunrise/sunset times. You would get the expected answer if our orbit was circular. The earth is in fact slightly closer to the sun (and travelling faster along the orbital path) in the northern hemisphere winter than we are in summer.

              Our shortest day of total daylight (always the first day of winter, the solstice) does not correspond to the date of our closest approach to the sun, which is by coincindence just a couple of weeks later. It's somewhat complicated math, but if you work out calculations of the spinning earth traveling along the ellipse, along with the direction in space of the earth's axis tilt and the time the sun appears on the horizon, then you get a slight offset from intuitive earliest/latest sunrise/sunset times.
              Yep, good info there.
              Also, and this plays into it, we measure time a little funny. We use the sun to reference a point on earth as a daily 'noon'. This is a little inexact cuz as the earth spins from day to nite it also revolves around the sun. This slightly affects the daily noontime - basically a moving target. A more accurate method of keeping time is to measure it against a distant star as it has almost no 'apparent motion' in relation to the earth.

              I luv this stuff, very cool
              Walk Softly

              Comment


              • #8
                Originally posted by AlpineSummit View Post
                Yep, good info there.
                Also, and this plays into it, we measure time a little funny. We use the sun to reference a point on earth as a daily 'noon'. This is a little inexact cuz as the earth spins from day to nite it also revolves around the sun. This slightly affects the daily noontime - basically a moving target.
                If you can still find a schoolhouse globe (in a library maybe), look for that funny figure "8" diagram, usually drawn in the Pacific Ocean. That's called an "analemma" (Google or Wikipedia it). If you learn how to read it, it will tell you the "equation of time" - the difference between clock time and apparent solar time because of our lopsided orbit - which is what AlpineSummit is talking about here.
                Originally posted by AlpineSummit View Post
                A more accurate method of keeping time is to measure it against a distant star as it has almost no 'apparent motion' in relation to the earth.
                Measuring time by the stars is called "sidereal time", it is indeed used by astronomers. The problem is it has no relationship whatsoever to what the sun is doing and would be very confusing to us who prefer the sun to be somewhere mid-sky when the clock says 12 noon.

                A really good observational astronomy site is heavens-above. Besides natural phenomena, it gives satellite visibility predictions for your location. This week would be a particularly good time to see the ISS and Space Shuttle together. Also be sure to check out Iridium flares.
                Last edited by Nessmuk; 12-11-2006, 07:20 AM.
                "Leave the beaten track behind occasionally and dive into the woods. Every time you do you will be certain to find something you have never seen before." - Alexander Graham Bell

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                • #9
                  I have always used the following link for sunrise/sunset:

                  http://aa.usno.navy.mil/data/docs/RS_OneYear.html

                  It allows you to input your city and state rather than lat/long and you can print out the chart for one year (or one day)

                  For where I live, it says the earliest sunset for this year is 4:29pm from Dec 4th to Dec 12th and on Dec 13th, it starts to go back to 4:30....and later and later...

                  For Sunrise, I haven't printed out next year yet but it shows that the latest doesn't arrive til 2007 because it shows my sunrise going later and later til Dec 31st being 7:22am.

                  It could be a slight function with where you live though as mentioned above... I'm in northern NJ so I am just an itty bitty bit south of the ADks, latitude wise.

                  Jay

                  p.s. I use this for my bike commute so I know when to install my super bright bike lights (bright but heavy!), otherwise I use a simply 4-AA LED light (lightweight)

                  Life is a short, warm moment
                  And death is a long cold rest.
                  You get your chance to try in the twinkling of an eye:
                  Eighty years, with luck, or even less.
                  -Pink Floyd

                  Comment


                  • #10
                    That's a good site.
                    Here's another, go halfway down the left column & see the Astronomy heading.

                    http://www.wunderground.com/cgi-bin/...st?query=12941
                    Walk Softly

                    Comment


                    • #11
                      Originally posted by Nessmuk View Post
                      If you can still find a schoolhouse globe (in a library maybe), look for that funny figure "8" diagram, usually drawn in the Pacific Ocean. That's called an "analemma" (Google or Wikipedia it). If you learn how to read it, it will tell you the "equation of time" - the difference between clock time and apparent solar time because of our lopsided orbit - which is what AlpineSummit is talking about here.
                      I have to say, as someone that has can add absolutely no value to the discussion here, I am quite fascinated by the discussion and have enjoyed the links and suggestions.

                      I've not pondered the topic all that much in the past, but it has been fun listening in on this one. I suppose that is one of the things I enjoy about places like this
                      "The forest is the poor man's overcoat. " Old Northeastern Proverb

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                      • #12
                        Originally posted by Nessmuk View Post
                        The earth's orbit is not exactly circular, darn close, but not quite.
                        As soon as I saw RS's post referring to sunsets in the NE vs. at the Arctic Circle, I knew we were headed here. And as soon as I saw the above, I said, "Aha! Sidereal days!" Which is of course, where we went next.

                        I covered this stuff a little bit in college and in my younger days when I was something of an amateur astronomer. Fun and interesting, but it can start to make your head spin at times! IIRC, the differences between "apparent time" and "sidereal time" cause us to lose something like four seconds a day in "apparent time," so we add a February 29 every four years in order to catch back up. Apologies in advance if I'm way off here or otherwise straying too far from the topic.

                        Thanks for the info, everyone!
                        46/46, 12/48, 58/115
                        46-R #6866

                        Comment


                        • #13
                          Originally posted by AdkWalrus View Post
                          IIRC, the differences between "apparent time" and "sidereal time" cause us to lose something like four seconds a day in "apparent time," so we add a February 29 every four years in order to catch back up.
                          Almost... the difference is actually 4 minutes (not seconds) a day. Note that 4 minutes x 365 days = 24 hours (approx). That makes sense if you think about what a sidereal day is vs a solar day terms of changing view angle of the sun, vs angle of the stars in the course of one full orbit (one year).

                          Looking at it another way, each solar day (what our clocks read) puts us 1/365th of the way further around the circle of our orbit. Since the earth rotates counterclockwise as it travels counterclockwise around the sun, picture that it takes a tiny extra 1/365th of a rotation (4 minutes) to put the sun at the same angle each day, say at noon. Therefore the stars appear in the same positon 1/365th of a circle (4 minutes) earlier as measured relative to our 24 hour solar day.

                          The 29 Feb leap year is something entirely different and is not related to the rotation rate of the earth in the way you are thinking. It takes (approx) 365.25 earth rotations (days) for us to complete one full trip around the sun, but we only count it as 365 whole days on the calendar. So we have to add a day every 4 years to keep the calendar constant with the seasons. Otherwise, in a few years of accumulating the quarter day calendar error we'd eventually have snow in July!.
                          Last edited by Nessmuk; 12-11-2006, 01:19 PM.
                          "Leave the beaten track behind occasionally and dive into the woods. Every time you do you will be certain to find something you have never seen before." - Alexander Graham Bell

                          Comment


                          • #14
                            Originally posted by Nessmuk View Post
                            If you can still find a schoolhouse globe (in a library maybe), look for that funny figure "8" diagram, usually drawn in the Pacific Ocean. That's called an "analemma" (Google or Wikipedia it). If you learn how to read it, it will tell you the "equation of time" - the difference between clock time and apparent solar time because of our lopsided orbit - which is what AlpineSummit is talking about here.
                            Whenever my winter camping buddy and I would take off for a day hike we would walk 20' along our shadow on the lake. Upon our return we would do the same thing, measure the angle between each track, divide by 15 and use the product to determine our hiking time in hours. Except it didn't quite work when checked against a watch. I remember someone using the analemma in illustrating why not.

                            I still don't quite get it because I see the earth spinning on a central axis therefore 15 degrees = 1 hour don't it? I would have thought that even with the 23 or 24 degrees of axix tilt that the sun would appear to shift 15 deg/hour.
                            1111111111

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                            • #15
                              Originally posted by Neil View Post
                              Whenever my winter camping buddy and I would take off for a day hike we would walk 20' along our shadow on the lake. Upon our return we would do the same thing, measure the angle between each track, divide by 15 and use the product to determine our hiking time in hours. Except it didn't quite work when checked against a watch. I remember someone using the analemma in illustrating why not.

                              I still don't quite get it because I see the earth spinning on a central axis therefore 15 degrees = 1 hour don't it? I would have thought that even with the 23 or 24 degrees of axix tilt that the sun would appear to shift 15 deg/hour.
                              The Sun does move 15 degrees per hour (roughly), but in its direction of travel, which is not the same as straight across the sky, except briefly around local noon. Your method will work ok then, but not well at other times.

                              Consider late in the day in the summer. The sun is setting almost vertically, so your shadow isn't moving much, it's just getting longer.
                              Tom Rankin - 5444W "In the depths of Summer, I finally learned that there lay within me an invincible Winter"

                              Proud Member #0003 of ADKHP Foundation
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