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Does the Sun Rise in the East?

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costean
121093.  Sun Nov 26, 2006 5:21 pm Reply with quote

The simplified question was, if you were standing on the equator, from which direction would you see the sun rise over the ocean at the time of the winter solstice?

Answer 113 deg.

The question I wanted to ask was, does the sun rise in the east and set in the west? And the answer, rather pleasingly, is no it doesn’t, but with two exceptions. These are at the times of the equinoxes, (which occur on or around the 21st Mar and the 21st Sep each year), irrespective of where you are on the globe.

The Earth is tilted at an angle of approx 23.5 deg from the vertical and this is what gives the Earth its seasons and the varying positions for sunrises/sunsets, as this diagram shows.
Diagram Earth’s tilt


In Britain in winter, roughly speaking, the sun will rise in the south east and set in the south west and conversely it will rise in the north east and set in the north west in the summer. This effect is magnified the further north you are and inside the Arctic Circle the sun never rises during mid-winter or sets during mid-summer; it is lessened the closer to the equator you are.

This diagram shows this effect for someone standing at a latitude of 40 deg North; roughly where Madrid is.
Earth tilt


The horizontal direction of the Sun at sunrise or sunset is known as the azimuth. So, as the earth is tilted at an angle of approx 23.5 deg, on the equator at the winter solstice the azimuth will be 113.5 deg, east (90 deg) plus 23.5 deg. And hence, at the summer solstice it will be 66.5 deg, east (90 deg) minus 23.5 deg. And consequently at the equinoxes (precisely in the middle of the periods between these times) the sun will rise at 90 deg (due east) and set at 270 deg (due west).

Source:
Being puzzled by my own observations of the positions of the rising and setting sun.


Here is a web sunrise/sunset azimuth calculator – enter city, hit ‘See’ and then select azimuth from the right-hand drop-down menu.
Sunrise/Sunset Azimuth calculator


QI titbit - Sun compasses

It is possible to navigate using the sun with a very simple device called a sun compass. There is good evidence that the Vikings used these for navigation. It is not really relevant here but for those of you who are interested please see the links below.
Sun Compass
Robin Knox-Johnson - Sun Compass
Viking Sun Compass

 
andymac
122920.  Sat Dec 02, 2006 1:56 pm Reply with quote

Well, technically, if we're being pedantic (and this IS QI) the sun doesn't rise at all, it just sit's there and bits of the earth 'sink'...

 
50scarrow
125316.  Sat Dec 09, 2006 2:39 pm Reply with quote

andymac wrote:
Well, technically, if we're being pedantic (and this IS QI) the sun doesn't rise at all, it just sit's there and bits of the earth 'sink'...


Being even more pedantic, the sun, like every other object in the universe, is moving.

 
grizzly
125385.  Sat Dec 09, 2006 7:58 pm Reply with quote

and so does the entire solar system...

and the entire galaxy...

 
gerontius grumpus
125387.  Sat Dec 09, 2006 8:04 pm Reply with quote

On average, the sun rises in the east and sets in the west.

 
djgordy
125418.  Sun Dec 10, 2006 4:28 am Reply with quote

Suppose that "east" is "the direction from which the sun rises".

 
Stephanee
125550.  Sun Dec 10, 2006 3:08 pm Reply with quote

I don't know why but it sounds better that the sun would rise in the west and sink in the east. It just does.....to me
Things seemed easier when the world was flat. :)

 
cornixt
125740.  Mon Dec 11, 2006 7:48 am Reply with quote

Why does the diagram have the 'ox' part of 'equinox' joined up? And there seems to be a tail on the 'e' in 'solstice'.

 
mei
524668.  Thu Mar 19, 2009 4:53 pm Reply with quote

costean wrote:

The horizontal direction of the Sun at sunrise or sunset is known as the azimuth. So, as the earth is tilted at an angle of approx 23.5 deg, on the equator at the winter solstice the azimuth will be 113.5 deg, east (90 deg) plus 23.5 deg.


Can anyone explain the reasoning there?
That little 'so' is very cheeky for something so far from obvious.

 
bobwilson
524671.  Thu Mar 19, 2009 5:03 pm Reply with quote

Related factoid

Panama is situated in Central America and therefore has the Pacific Ocean to the west, and the Atlantic to the East. Nonetheless, because of the horizontal "S" shape of the country, it is possible to watch the sun rise over the Pacific (the "Western Ocean") and set over the Atlantic (the "Eastern Ocean") in Panama.

 
Davini994
524743.  Thu Mar 19, 2009 7:57 pm Reply with quote

mei wrote:
Can anyone explain the reasoning there?


Sunrise is when you move from dark to light; have a looksie at the picture at the top of the page; the left hand one is winter. Imagine moving from dark to light in this configuration.

In winter, the northern point of the axis of the earth is pointed away from the sun. So when the sun rises, East is 'pointing' above the sun on the diagram.

So if we are looking at the sun, we are looking below due East (90 degrees). Itt's at the sum of the tilt (23.5 degs) and 90 degs, i.e. 113.5 degs.

Hopefully that makes sense. It might not. Or it might be wrong.

There's this thread too.

Welcome by the way mei!

 
Southpaw
524771.  Fri Mar 20, 2009 3:35 am Reply with quote

It's the equinox today, sun-fans, so if you want to check all this out with a compass, be outside at about 6:19pm.

 
mckeonj
524779.  Fri Mar 20, 2009 4:05 am Reply with quote

But only if you live along the Greenwich Meridian; for me in SW Ireland it's more like 7pm.

 
mei
524784.  Fri Mar 20, 2009 4:20 am Reply with quote

Thanks!

I eventually figured it out myself, and it's as Davini994 says (I think)

This might not be legible ;-)



Hello!

 
djgordy
524818.  Fri Mar 20, 2009 6:05 am Reply with quote

Southpaw wrote:
It's the equinox today, sun-fans, so if you want to check all this out with a compass, be outside at about 6:19pm.


According to the National Maritime Museum, and various other sources, the equinox will be at 11:43 am so there is just under half an hour of winter left. At last I can remove these thermal long johns I have been wearing for the last three months.

http://www.nmm.ac.uk/explore/astronomy-and-time/time-facts/equinoxes-and-solstices

http://www.timeanddate.com/calendar/march-equinox.html

 

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