The ''rising and setting'' of the sun

Discussion in 'General Science & Technology' started by wegs, Jan 8, 2020.

  1. exchemist Valued Senior Member

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    11,571
    Did you notice it sliding along the horizon as it rose, in accordance with Janus's explanation? Or are you in the Tropics, where this is less marked?
     
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  3. wegs Matter and Pixie Dust Valued Senior Member

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    I'm in the southern US, and I tried to pay attention more so this morning, per this thread. It seemed to ''start'' (or at least what I first noticed of it) from the right, and then it ''moved'' slightly to the left. My left and right, from where I was sitting. Now, it's ''hiding'' behind the clouds.
     
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  5. exchemist Valued Senior Member

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    That's curious. It should by rights move towards the South as it rises, which would be on your right as you look East.
     
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  7. wegs Matter and Pixie Dust Valued Senior Member

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    It's ''overhead'' right now at 9:15 AM ET, but it ''started'' from the right. Not directly overhead, by noon it will be.
     
  8. DaveC426913 Valued Senior Member

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    In this diagram we are looking East. In the Winter the Sun will rise in the SouthEast, on a slant upward to your right (i.e. it will move southward as it rises).
    It will not peak overhead (it can only do that in the summer), but will peak at noon somewhere around (90-23.5-~30ish=) 35-45 degrees in the sky.

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  9. wegs Matter and Pixie Dust Valued Senior Member

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    Okay, thanks. So now, it’s to my right, not totally overhead but if I were looking at a clock’s face, it would look like the sun is at 2 PM.

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  10. sideshowbob Sorry, wrong number. Valued Senior Member

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    I saw the sun rise this morning too - about 9 AM.

    I live at approximately the 51st parallel. At this time of year, the sun rises in the southeast and doesn't get very high above the horizon before it sets in the southwest (around 5 PM).

    To throw another spanner into the works, the moon rises much farther to the north and much higher in the sky. I wonder if anybody might like to expound on the differences between sunrise/set and moonrise/set.

    For entertainment only:

    "By the rising of the moon, by the rising of the moon
    And a thousand pikes were flashing by the rising of the moon"
    -- The Dubliners​
     
  11. Janus58 Valued Senior Member

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    2,318
    m the moon, s is the Sun, the\ is the Earth's axis of rotation. below is the arrangement in Winter (North pole up) the Moon is shown as it passing its highest point at night.
    m.....\..............s
    North pole leans away from Sun, thus sun rises lower in day time sky. North pole leans toward Moon, thus night time moon appears higher in sky. Essentially the ecliptic is low in the Winter daytime sky and high in the Winter nighttime sky
    In addition, the Moon's orbit is tilted at ~5 degrees to the ecliptic. Thus it can be 5 degrees higher or lower than the ecliptic in the sky. This changes from year to year as the Moon's orbit precesses over 18.6 years ( If one Winter, the Moon appears 5 degrees higher in the sky than the ecliptic at night, 9 years later it will be 5 degrees below the ecliptic at night. So, for you, at the 51st parallel, the Moon could get as high as 67 degrees above the horizon in Winter when things line up right.
     
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  12. wegs Matter and Pixie Dust Valued Senior Member

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    8,808
    The sun ''rose'' this morning, angled a little more to the left of where I was seated. Now, it's 10:35 AM ET and if I were looking at a watch/clock face, the ''time'' would be 1 PM.

    Will the sun reach an angle of 90 degrees (appearing directly overhead as an observer) only nearest to the equator?
     
  13. sideshowbob Sorry, wrong number. Valued Senior Member

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    7,053
    Thanks for the explanation. I had an inkling - maybe I have heard it before - but now it makes more sense. luckily this topic came up when the moon happens to be high.

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  14. exchemist Valued Senior Member

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    The sun only reaches a point directly overhead at noon within the Tropics. At the N Hemisphere Winter solstice it is overhead at noon at the Tropic of Capricorn. At the N Hemisphere Summer solstice it is overhead at noon at the Tropic of Cancer. At the equinoxes, it is overhead at the equator itself.

    In between, it is overhead at noon at a point that moves from one tropic to the equator to the other tropic and back again.
     
  15. DaveC426913 Valued Senior Member

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    17,480
    Sorry, this doesn't really tell us much.

    This doesn't really tell us much either.

    We don't know where you are seated or what direction you are facing. If you're facing NorthEast then 1PM would still be North of Due East.
     
  16. wegs Matter and Pixie Dust Valued Senior Member

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    8,808
    I was facing North.
     
  17. Neddy Bate Valued Senior Member

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    2,411
    That image is also analogous to a globe of the earth. The Polaris star is analogous to the globe's north pole, the ecliptic/equinox is analogous to its equator, and the solstices are analogous to the globe's Tropics of Cancer & Capricorn. So holding a globe on an angle so that its north pole points toward the real Polaris star will let you use the lines of the Tropics and the equator to predict the sun's path at the solstices and equinoxes, as viewed from your location.

    So, if you were on the north pole, you would hold the globe so that the north pole points straight up, and this would demonstrate why the sun is not visible during the winter, because the sun would be too far south to be seen from that vantage.
     
    Last edited: Jan 11, 2020
  18. DaveC426913 Valued Senior Member

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    17,480
    OK, that's getting more confusing then.

    If you are facing North, and
    "The sun rose this morning, angled a little more to the left of where I was seated."
    What do you mean by "to the left"? Because, to me, that would seem to be West of North, or North Northwest.

    and
    "Now, it's 10:35 AM ET and if I were looking at a watch/clock face, the ''time'' would be 1 PM."
    That would seem to be a little East of North, or North Northeast.
     
  19. wegs Matter and Pixie Dust Valued Senior Member

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    8,808
    I need a compass. I’m being serious.
     
  20. exchemist Valued Senior Member

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    11,571
    Not for this exercise. You just assume the sun rises in the East (OK a bit South of East at this time of year) then moves round to the South and sets in the West. So if you face East, it rises a bit to the right of straight ahead, moves up and to the right until noon, then moves down and back to the left again, setting behind you.
     
  21. DaveC426913 Valued Senior Member

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    17,480
    Actually Google Maps will show you North where you live. Zoom in on your house. North is top of screen.
     
  22. wegs Matter and Pixie Dust Valued Senior Member

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    8,808
    Okay, thanks exchemist and Dave. So, the sun always ''rises'' in the east and sets in the west. I've read that if I'm walking towards the sun, I'll then be heading south. I don't get it.

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    Can someone help me understand this?

    https://www.mathsisfun.com/measure/compass-north-south-east-west.html

    My question has to do with the middle of the page - I don't understand ''three figure bearings.'' Just curious as to how all of those ''bearings'' could represent North?
     
  23. exchemist Valued Senior Member

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    11,571
    AARRGH! Oh God, no, wegs, please.

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    To use the sun to find directions you need to know the time of day. Obviously. Because at sunrise it is in the East, at noon it is due South, and at sunset it is in the West.

    I use the sun quite often when I am out walking in unfamiliar places, to orient myself approximately so I can read the map properly. Mind you, in the British climate, one is sometimes hard put to work out what faint patch of brightness in a generally grey sky is where the sun is hiding! But I always check my watch when I do this - and also keep in mind whether we are on GMT or Summer time, since on Summer time the sun is due South at 1300, not 1200.
     

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