----------------------------Original message---------------------------- Quite right! Think of it this way, the sun is always N,E,S,W of us at 12 mn (N. Hem), 0600, Noon (N. Hem.), 1800 local time (i.e. forgetting the averaging effect of time zones) It moves through 15 degrees of longitude/bearing per hour (360 degrees in 24 hours). It is always in this position at these times every day, but only twice a year everywhere on the equinoxes does it rise and fall exactly (or nearly so) at the horizon E-W. The rest of the time the sun is at those positions above the horizon (in summer) or below (in winter). In the polar regions it is still in those directions in summer (when it never crosses below the horizon) and in winter (when it never crosses above). You just have to think of the sun being behind or 'through' the earth relative to you at times when you cannot see it. But it does still have a bearing relative to you - see the globe. iain taylor [log in to unmask] _______________________________________________________________________________ Subject: Sunrise...Sunset...180 Degrees Author: Maps and Air Photo Systems Forum <[log in to unmask]> Date: 29/6/1995 3:27 PM 2 messages.---------------------------Johnnie ---------------------------------------------------------------- : [log in to unmask] (Jim Carter) : Re: Sunrise...Sunset...180 Degrees : Wed, 28 Jun 1995 16:06:57 -0500 (CDT) > > 180 degrees from sunrise to sunset could never happen north of > Cancer or south of Capricorn. Regardless of the time of year north of > Cancer, sunrise is still in the southeast with sunset in the southwest, > just at varying degrees. South of Capricorn, sunrise is always in the > northeast and sunset in the northwest. Only between Cancer and > Capricorn could you ever have 180 degrees from sunrise to sunset since > it is only in that range that the Sun would ever pass directly > overhead. At least that's as I understand it... > And I remember when the author of this was one of my students. Luckily, he did not take physical geog or climatology from me. I wanted to get my copy of Wm. Sellers, Physical Climatology, in front of me before I took on this issue. In this classic text, dated about 1965, the author copies a number of the sun position diagrams. Those diagrams are reproduced from an earlier Meteorological monograph. In that monograph there is a diagram of sun position for each 5 degrees of latitude. These diagrams show the position of the sun relative to North for various times of the year. They also show the height of the sun above the horizon. Sellers also gives the equations to solve for these values. The quote above has to be wrong. North of the Arctic Circle the sun will rise in the north and set in the north at least twice during the year. Depending how far north you go, the sun will never set for part of the year. So, in this area the sun will trace out a 360 degree arc part of the year. South of the Arctic Circle, the sun will rise in the north half of the sky from March 22 through September 20, or so. (Applicable only in the Northern Hemisphere.) The further north you go, the more northern the arc will be at sunrise and sunset. If you have not done so, let me suggest you mark the compass position of the sun at sunrise, or sunset, for the Summer Solstice, Equinox, and Winter Solstince. I was able to do that on my deck in Knoxville. It is interesting to see how much difference there is in the position of the sun at sunrise and sunset throughout the year. And, get a copy of Sellers and look at those diagrams. They are important tools for architectual design. I suspect the diagrams have been reproduced elsewhere. When I get a chance, I'll pull out my copy of Sellers, look at some topos of NYC, and revisit this discussion. BTW; how did folks work out Stonehenge without the use of email? Jim Carter, Illinois State University ------------------------------------------------------------------ : Wed, 28 Jun 1995 15:19:08 -0700 : [log in to unmask] (Paul R. Larson) : Re: Sunrise...Sunset...180 Degrees >----------------------------Original message---------------------------- > > > 180 degrees from sunrise to sunset could never happen north of > Cancer or south of Capricorn. Regardless of the time of year north of > Cancer, sunrise is still in the southeast with sunset in the southwest, > just at varying degrees. South of Capricorn, sunrise is always in the > northeast and sunset in the northwest. Only between Cancer and > Capricorn could you ever have 180 degrees from sunrise to sunset since > it is only in that range that the Sun would ever pass directly > overhead. At least that's as I understand it... > > Eric The above explanation misses something. A question on my physical geography test goes as follows: "If the vertical sun at the June solstice only reaches 23.5 degrees North latitude, why does the early morning and late evening sun shine directly into the windows on the NORTH side of my house, which is located at 40 degrees north latitude?" The answer, of course, is that the path of the sun across the sky is an arc, not a straight line. The earth is a spheriod, not a cylinder. At solar noon on the June solstice, the sun is to the south of my position (40 degrees North latitude) at an altitude of 72.5 degrees above the horizon. But, in the morning and evening, the sun is rising and setting in the northeast and northwest respectively. At equinoxes the sun rises directly east (90 degrees) at every point on the earth. (Use a globe and check it out.) As the position of the vertical sun moves toward the north following the March equinox, it rises in the northeast and sets in the northwest (for the entier six month period). It then crosses the sky in an arc, reaching its highest point at noon, as noted above. That is why streets oriented from northwest to southeast in Manhattan are parallel to the Sun's rays at sunset on the June solstice. At the December solstice, sunrise should be just the opposite, or parallel to the streets from the other direction. At this time of year in Tennessee you will note the same phenomenon. The sun at sunrise and sunset will be illuminating the NORTH side of buildings. Sunrise and sunset are not in the southeast and southwest from the March equinox until the September equinox. Use a globe to help you visualize this phenomenon. Tilt the globe as it would be at the solstice. Position yourself as if you were the Sun, with the axis inclined directly toward you. Then, place a small block of wood or other object, at your latitude. Rotate the globe from sunrise to sunset. At sunrise and sunset, which side of the block do you see? I do not like to use the terms Summer solstice and Winter solstice, nor Spring and Autumn equinox. These terms only apply to one hemisphere while the other hemisphere is exactly opposite. In order to make the terms applicable to the entire globe, I refer to them as June and December Solstice, and March and September equinox. I hope that this will shed some "light" on the subject. Paul R. Larson Assistant Professor, Geography SC 309 Southern Utah University Cedar City, Utah 84720 tel: (801) 865-8244 fax: (801) 865-8051 E-mail [log in to unmask]