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Q: In what direction does the Sun travel relative to the calendar year? ( Answered ,   11 Comments )
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 Subject: In what direction does the Sun travel relative to the calendar year? Category: Science > Astronomy Asked by: twbt-ga List Price: \$5.00 Posted: 24 Jul 2004 13:12 PDT Expires: 23 Aug 2004 13:12 PDT Question ID: 378584
 ```As I understand the cosmos the sun is orbiting the center of the milky way, "dragging" the earth along with it. I'd like to know in what direction the sun is headed relative to the calendar year? A made up answer would be "the sun is headed in the direction of June 13th"```
 Subject: Re: In what direction does the Sun travel relative to the calendar year? Answered By: digsalot-ga on 24 Jul 2004 20:32 PDT Rated:
 ```Hello there The Sun is indeed in motion. It orbits the center of our galaxy at the speed of approx 155 miles per second in a counter-clockwise direction. And of course we are moving right along with it, being "dragged" as you put it. It takes the Sun (and us) about 200 - 250 million years to orbit once around the center of the Milky Way Galaxy. So yes, the Sun does have a "year" as well - about 200 million times or so as long as an Earth year. The analogy of the CD spinning around a non-moving center mentioned in the comment section leaves much out of the equation. While the CD disk is spinning around its center, the CD center is moving at considerable speed as the Earth rotates. at the equator, that would be about 1670 km'hr or about 1070 miles per hour. To find the rotational speed where you live, take the cosine of your latitude, and multiply it by the speed at the equator. For example, the speed at a latitude of 60 degrees, the speed would be cos(60)x1670=835km/hr. So now we have that CD spinning around a center which itself is moving at over a thousand miles per hour because it is on the surface of the Earth. Now while that disk is spinning around its center and the CD center is spinning around the Earth, the Earth itself is orbiting the Sun at about 18½ miles per second - and of course the sun is moving at about 155 miles per second. So the analogy of the "motionless" center of the CD disk falls far short. To answer your question - what direction the Sun is headed relative to "Earth's" calendar year? - - it is headed counter-clockwise around the center of the galaxy at 155 miles per second and at the end of the calendar year is approx 1/200 to 1/250 millionth further along the path than it was at the beginning of the calendar year. And please don't forget, our galaxy is orbiting within a larger galactic cluster which in turn is orbiting an even larger cosmic structure right up to where everything is orbiting something which might be called the "center of the universe" itself. - - which of course is me - - and I can prove it by means of concentric circles. <-- feeble attempt at humor. I'm getting dizzy. Search - Google Terms - orbital speeds After chasing these web sites several thousand miles through space (really, as you now know) - I used the following to compose the answer. http://searchsmallbizit.techtarget.com/sDefinition/0,,sid44_gci849653,00.html - "Earth's mean orbital speed" - From searchSmallBizIT.com http://www.enchantedlearning.com/subjects/astronomy/solarsystem/where.shtml - information about the Sun's galactic orbit from enchanted learning.com http://www.windows.ucar.edu/tour/link=/kids_space/qearth_motion.html - "Quickie Questions - Extraordinary Earth - Movement of the Earth" - From University Corporation for Atmospheric Research If I may clarify anything, please ask. Cheers Digsalot``` Request for Answer Clarification by twbt-ga on 25 Jul 2004 10:27 PDT ```Hello, Unfortunately you didn't answer my question at all :) though of course I appreciate the detail you went into answering the question you thought I asked. I still believe the premise for my question is valid, so I will reword it in the hopes that its logic is more clear (I could resubmit the question if desired, i'm easy going..) Here it is reworded. PREMISE: 1. The earth has an orbit around the sun. Any position in that orbit corresponds to a day on the calendar year. (i.e. when the earth is "left" of the sun its October, I'm guessing on the month, but the point is that there has to be a corresponding month to the point in the orbit of the earth where it is located directly "left" of the sun) 2. I don't care where the earth is at all in the equation. 3. The Sun is moving in a straight line (yes it must be moving in a curve but let's assume to make things simpler that the distances involved here are small enough that the curve will appear to be a straight line Now let's jump to an analogy. I have a marble that represents the sun. Immediately around it I have traced a circle in chalk that represents the orbit of the earth. Clearly the moving sun must CROSS the chalk circle since it is moving. Since it is moving in one direction only, then it can only cross the chalk circle at ONE point. Let's call that POINT X. Point X is a point on the chalk circle... which is a point on the orbital path of the earth... which has a calendar date associated with it. Therefore The sun crosses the orbital path of the earth at a specific point, that has an associated calendar date with it. My question is: What is that date?``` Clarification of Answer by digsalot-ga on 25 Jul 2004 13:31 PDT ```Hi again AHA! - your restatement of the question creates a new clarity. Sorry I misunderstood the first time. The answer is the day of the northern Winter Solstice. The northern summer takes place when the Earth would be positioned to the "right" of the Sun as you use in your analogy.. That is when the northern hemisphere is tilted most directly toward it. Remember, the Earth orbits in a counter-clockwise direction so it should be easy to visualize. As the northern hemisphere moves into autumn, the Earth has moved approx one quarter of its orbit and is now directly in "front" of the sun as the Sun moves on its orbit around the galaxy. So we now know that the 'figurative' crossing of the Earth's orbit by the Sun's orbit takes place sometime in the northern autumn. Actually in the very last instance of the northern autumn or the first instance of the northern winter, whichever way you want to look at it. When we consider that both the Earth and the Sun have counter-clockwise orbits, the earth is directly in 'front' of the Sun's direction of travel on the day of the Winter Solstice. - the 21st or the 22nd of December, depending on the year. I have posted a diagram which might make the explanation a little easier. The direction of the solar galactic orbit is from bottom to top and the positioning of the Earth's orbit is marked by season. Both orbits are counter-clockwise. The solar orbit is based on the presumption it is a straight line, though we know it is actually a curve. This file is a temporary posting which will vanish in a few days so if you want a copy of it, do it soon. Link for your file is : http://68.15.21.151/uploads/researchers/Earthorb.gif Still dizzy Digs``` Clarification of Answer by digsalot-ga on 25 Jul 2004 18:40 PDT ```A further narrowing down of the date thanks to efn-ga. Since we are dealing with a hypothetical fixed point where the planet earth is in its orbit on the Winter Solstice, it takes a fraction over 7 days for the Sun to reach that point. In 7 days, the sun will have moved 93,744,000 miles along its path. So if you wish we can make the date for the Sun crossing that hypothetical point on Dec. 28. You can accept that or winter soltice, whichever one you want. Now I can blame efn-ga for making me dizzy - though I'm glad he did. Digs``` Clarification of Answer by digsalot-ga on 30 Jul 2004 11:02 PDT ```Thank you for the kind words and the extra. Please keep us in mind if we can of service in the future. Digs```
 twbt-ga rated this answer: and gave an additional tip of: \$1.00 `Thanks for answering my question perfectly. The diagram was helpful too.`

 Subject: Re: In what direction does the Sun travel relative to the calendar year? From: crythias-ga on 24 Jul 2004 19:25 PDT
 ```Since the earth orbits the sun eliptically (nearly a circle), the sun is almost always in the center of the earth's orbit. The year is determined by the earth's position in earth's orbit about the sun. A complete circuit is one earth year. So, unless you feel that the sun is orbiting the earth, the sun's position is not relative to the year. It's pretty much asking the question of where is the center of a CD heading relative to the spinning of the outside of the CD? It isn't moving. It could be moving, but the spin is also moving with the center. We'd actually be in trouble if the sun started to move very much with respect to the earth's orbit. It would mean that the planets, starting with Mercury, would be more affected by the Sun's gravitational pull at one part of the orbit, and possibly spin into the sun or out of the Sun's orbit. Each loss of an interior planet would affect the pull on subsequent planets. :) That thing about the earth orbiting the sun? http://roland.lerc.nasa.gov/~dglover/dictionary/y.html Year: A period of one revolution of the earth around the sun. :)```
 Subject: Re: In what direction does the Sun travel relative to the calendar year? From: crythias-ga on 25 Jul 2004 06:21 PDT
 ```Digsalot :) Hey, thanks for that information. Is the motion of the sun relative to the year significant? How much does 1/200 millionth mean in actual movement (distance, KM)? Also, I considered the CD center to be the motion of the sun, not the rotation of the earth... The CD's outside edge would have been the motion of the earth relative to the sun.```
 Subject: Re: In what direction does the Sun travel relative to the calendar year? From: efn-ga on 25 Jul 2004 12:25 PDT
 ```The question assumes that the earth's orbit around the sun and the sun's orbit around the center of the galaxy are in the same plane, but they are not. http://www.physicsforums.com/showthread.php?t=9666 http://amateurastronomy.org/Events/EH451.html We could project the earth's orbit perpendicular to the ecliptic plane to define a cylindrical surface and ask where radially on that surface the sun's galactic orbit would intersect it, to get a time of year answer. To make this meaningful, we would have to pick a particular time at which to project, since the earth's orbit is moving with the sun. --efn```
 Subject: Re: In what direction does the Sun travel relative to the calendar year? From: crythias-ga on 25 Jul 2004 13:04 PDT
 ```Efn, based upon your comment, there may not ever be a possibility that the sun crosses the orbital path of the earth, right? I really would be concerned that the sun would cross the orbital path of the earth. How close is the orbit of the earth in the nearest to the sun? How long would it take the sun to travel that distance? I'm willing to guess that it's not even close to one earth year. Even as fast as the sun might move, I think we'd really be in trouble if the sun ever came close to the orbit of the earth.```
 Subject: Re: In what direction does the Sun travel relative to the calendar year? From: neilzero-ga on 25 Jul 2004 13:34 PDT
 ```I think your question is valid. There should be a date (and time to the second) each year on which the Earth is circling the galaxy faster than the sun, by a maximum amount, and another date about 6 months later when Earth's speed is less than the sun by a maximum amount. The date will shift slightly due to leap year, and drift a few parts per billion each year. The tilt of the sun's path and the tilt of the Earth's path complicate the calculation, but IMHO there is an answer, and it is of some significance reguarding the speed (relative to Earth) at which particals pass though our solar system. Sorry, I don't know the dates. Neil```
 Subject: Re: In what direction does the Sun travel relative to the calendar year? From: crythias-ga on 25 Jul 2004 13:45 PDT
 ```Digsalot, you have the earth crossing the sun's orbit. When does the sun cross the earth's orbit, according to the clarification of the asker? Quote from twbt-ga: "Therefore The sun crosses the orbital path of the earth at a specific point, that has an associated calendar date with it. My question is: What is that date?"```
 Subject: Re: In what direction does the Sun travel relative to the calendar year? From: digsalot-ga on 25 Jul 2004 16:07 PDT
 ```Hi crythias-ga Take a look at the diagram again. As the sun moves forward, it crosses Earth's orbit on the winter solstice. While the diagram is stationary, the sun and earth are not. The Sun is moving forward at 155 miles per second. It will 'figuratively' cross Earth's orbit at the point of winter solstice a very short time after Earth has passed that point. Short enough that the event will take place within a few hours of the instant of solstice. We need to imagine that point when Earth reaches the solstice as being stationary while the Sun moves. Not a reality but necessary for the question. In reality, the Sun will never cross the Earth orbit because the earth orbit is moving forward at the same speed as the Sun since it is centered on the sun. It would, in diagram form, be a forward moving spiral rather than a circle. The hypothetical crossing of the Earth orbit by the Sun is as stated, winter solstice.```
 Subject: Re: In what direction does the Sun travel relative to the calendar year? From: efn-ga on 25 Jul 2004 17:30 PDT
 ```Digsalot, What's the evidence that the sun's galactic orbit moves it toward where the earth is on the winter solstice? I accept that if the equinoxes are to the right and left, the solstices are in front and behind in orientation. But this is just an arbitrary orientation, and I don't see what it has to to with the sun's orbit through the galaxy. Why couldn't we just as well say the solstices are to the left and right and the vernal equinox is in front, so the sun is going toward the vernal equinox? By the way, for those who are interested, it takes the sun about seven days to move in its orbit a distance equivalent to its average distance from the earth. --efn```
 Subject: Re: In what direction does the Sun travel relative to the calendar year? From: digsalot-ga on 25 Jul 2004 18:34 PDT
 ```Hi efn-ga - - You say the orientation is arbitrary? Not really. Since the orbital directions are counter-clockwise for both the Sun and the Earth, there is only one way we can orient it as a "map." The orbit of the Earth must move around the dot representing the Sun in that counter-clockwise direction and in this case, the orbit of the sun itself must be from the bottom of the page to the top, counter-clockwise around the galaxy. Nothing arbitrary about it. We must also take into account the Earth's 'tilt.' For the northern hemisphere to experience summer, that tilt must have the northern hemisphere pointed toward the Sun. On a map aligned with the counter-clockwise orbit, the earth must be to the "right" of the Sun on the map for that to happen. So once again, positioning is not arbitrary. But - and thank you - I did the calculations and it does take just over 7 days for the Sun to move that distance. I will correct my answer. LOL - If we want to take it to the ultimate - the Sun is 'always' crossing Earth's orbital path. Since the Sun takes 225 million years to orbit the Galaxy, it has done that many times in the 4.5 billion years of Earth history. The path is pretty well covered by now. Digs```
 Subject: Re: In what direction does the Sun travel relative to the calendar year? From: crythias-ga on 25 Jul 2004 20:29 PDT
 ```http://hypertextbook.com/facts/2002/StacyLeong.shtml The Sun has orbited the galaxy, more than 20 times during its 5 billion year lifetime. http://www.physicalgeography.net/fundamentals/6h.html (More info supporting the above comments)... But... what's keeping earth (or mercury, for that matter) from crashing into or careening off the Sun's orbit? It would seem that you have a Sun moving fast enough to be in the way of the earth's orbit if it were moving in the same plane, and then be so far out of the orbit that the earth couldn't orbit again. How does this get rectified? What are the angular momentums and ... Sorry, I will ask this in a real question...```
 Subject: Re: In what direction does the Sun travel relative to the calendar year? From: mawazi-ga on 09 Aug 2004 19:20 PDT
 ```I am perplexed by the answer. Does the orbital path of Earth rotate as Sun orbits the galactic center? Would not this have to be the case for the Winter Solstice to always occupy the point of the intersection? i.e. If the sun is located on the "left" side of its orbit, moving counter-clockwise "top to bottom", is Earth's orbital path rotated so that the Winter Solstice occupies the exact "bottom" of Earth's orbit? Or, does Sun in fact intersect at the Summer Solstice when it is located thus?```