solstice

[RogerS]

I find it quite depressing that someone thought it was necessary to add "The Sun and the Earth are not to scale in this drawing" to the bottom of that diagram... :/

It's taken from an American site...what do you expect? :lol:

 

[Dieseldog]

yep summer is on its way

 

[heimlaga]

It is rather obvious that people need a party in midst of this darkness. The time is half past 2 and within half an hour it will be dark again...........

Merry christmas to you all........ and just for the sake of argument I want to point out that the real christmas is celebrated today...... at least in my country :wink:

 

[Digit]

Which ever day, enjoy it and a happy new year to you.

Roy.

 

[Jonzjob]

It is rather obvious that people need a party in midst of this darkness. The time is half past 2 and within half an hour it will be dark again...........

Merry christmas to you all........ and just for the sake of argument I want to point out that the real christmas is celebrated today...... at least in my country :wink:

If that really is the case then why do they have the same celibrations in Aussie and Kiwi Land :? :? :? They have barbies on the beach instead an it stays early very late :?

 

[Jacob]

It is rather obvious that people need a party in midst of this darkness. The time is half past 2 and within half an hour it will be dark again...........

Merry christmas to you all........ and just for the sake of argument I want to point out that the real christmas is celebrated today...... at least in my country :wink:

If that really is the case then why do they have the same celibrations in Aussie and Kiwi Land :? :? :? They have barbies on the beach instead an it stays early very late :?

Longest day. Summer solstice. S'obvious innit.

 

[Jonzjob]

"It is rather obvious that people need a party in midst of this darkness."

When I were down there it weren't dark? Except when it was of course :? an that were when it stayed early late an not like up 'ere when it gets late early Jacob?

 

[JakeS]

When I were down there it weren't dark?

Tradition more than anything; having Christmas at a different time of year in the southern hemisphere just 'cause it's not so dark in December would make it a little more obvious that it has nothing to do with Christ's birthday than the church would like to let on!


Also there'd be those cheeky buggers who live near the equator and would celebrate it twice a year.

 

[dickm]

To be pedantic, whilst 21st Dec has the least daylight, the sun continues to rise later until 1st January. The earliest sunset occurs on 14th Dec. It's just that after 14th Dec, although the sun starts to set later, the sun rises later by a greater amount. Conversely, after 21st Dec, although the sun continues to rise later up until 1st Jan, it is setting later by a greater amount - hence why 21st Dec is the shortest day. This is all caused by the elliptical nature of the earth's orbit. In December when the earth is slightly nearer the sun it travels faster in its orbit so that it has to rotate further to show exactly the same face to the sun. In June when the earth is at its greatest distance from the sun it travels slower in its orbit and therefore it has to rotate slightly less to show the same face to the sun.

So now you know! I'll get me coat! :-#

Thanks for that, Roger - it's very obvious up here that sunrise keeps getting later (on the odd days when you can see the sun!) after the solstice, and I've wondered why this is. I nearly understand the explanation given, but still not quite; is there a website with pictures that explains it for the imaginationally challenged?

 

[Jacob]

....it's very obvious up here that sunrise keeps getting later (on the odd days when you can see the sun!) after the solstice, and I've wondered why this is. ...

Are you sure about this? It doesn't do that in London, unless it's in seconds, according to this.
In fact it's called the "solstice" precisely because you can't see much change in times i.e. the max/min declination of the sun appears to be standing still: barely changing for some days.

 

[Digit]

If you mean immediately after the solstice then no! But 'after the solstice' as **** said, then yes.

Roy.

 

[Travis]

It's taken from an American site...what do you expect?

Thanks for giving credit where credit is due--

Travis

 

[Jacob]

If you mean immediately after the solstice then no! But 'after the solstice' as **** said, then yes.

Roy.

It's no either way. Sunrise is latest at the solstice (by definition) and stays close to 8.06 am (in London) from Dec 26 to Jan 4, though there may be small deviations in seconds which wouldn't be noticeable staring up into the wintry dawn of a December morning north of Aberdeen, unless you were working away with sextant and chronometer.

 

[Digit]

Well Jacob, in my world Jan 6 comes after the solstice! Or some time before the next one if you insist!

Roy.

 

[RogerM]

It's no either way. Sunrise is latest at the solstice (by definition) and stays close to 8.06 am (in London) from Dec 26 to Jan 4, though there may be small deviations in seconds which wouldn't be noticeable staring up into the wintry dawn of a December morning north of Aberdeen, unless you were working away with sextant and chronometer.

Not really correct. The definition of the solstice is that it occurs on the 2 days in the year when the sun is furthest from the celestial equator - i.e. furthest north for the summer solstice (21st June) and furthest south when it's the winter solstice (21st Dec). In the northern hemisphere, these will be the dates of maximum(summer) daylight or minimum (winter) daylight hours. In the northern hemisphere these will be the days which have the longest and shortest time between sunrise and sunset, and would have been recognised by our distant ancestors as the days when the midday sun was at it's annual highest or lowest above the horizon..

However, as previously mentioned, although the day with the least daylight in the northern hemisphere occurs on 21st Dec (hence it defining the winter solstice), this is not the date of the latest sunrise or the earliest sunset. In the time the earth rotates through 360 degrees on its axis it also travels around the sun in its orbit. Given that there are 365 days in a year and 360 degrees in a circle, the earth has to rotate approximately 361 degrees before the same face is precisely orientated toward the sun. If the earth's speed around the sun was constant there would be no problem, but it isn't. Because the earth's orbit is slightly elliptical, when the earth is at it's closest to the sun which occurs in December (Perihelion) it travels faster in its orbit than when it is at it's furthest (Aphelion). When it travels fastest (and therefore further along its orbit in the time it takes to complete one 360 degree rotation), the earth has to rotate slightly more to present the same face to the sun in December than it does in June.

This is why the earliest sunset occurs around 14th Dec and the latest sunrise occurs around 1st January (it is not precisely the same each year - don't mention the celestial mechanics of leap years or the "precession of the equinoxes"!). However, the shortest hours of daylight (i.e. the shortest time between sunrise and sunset) will still, by definition, be on the winter solstice on 21st Dec. If you think that this all sounds very pedantic, and an exercise in semantics, you would be right. but it is an interesting point of discussion and it's nice to understand the workings of the world around you! :lol:

 

[Jonzjob]

An they were eye thinkin that the winter one were when it got late earliest an the summer one were when it stayed early latest :shock:

Nuffin wrong wiv the 29th Feb. It's me weddin aniversary :mrgreen: :mrgreen:

 

[dickm]

Thanks for the further explanation, Roger, but I'll just have to try and draw it out with pencil and paper to really understand. :roll:

But it's nice to think that ultimately, it will be light at 8:0am......

 

[Jacob]

It's no either way. Sunrise is latest at the solstice (by definition) and stays close to 8.06 am (in London) from Dec 26 to Jan 4, though there may be small deviations in seconds which wouldn't be noticeable staring up into the wintry dawn of a December morning north of Aberdeen, unless you were working away with sextant and chronometer.

Not really correct. The definition of the solstice is that it occurs on the 2 days in the year when the sun is furthest from the celestial equator - i.e. furthest north for the summer solstice (21st June) and furthest south when it's the winter solstice (21st Dec). In the northern hemisphere, these will be the dates of maximum(summer) daylight or minimum (winter) daylight hours. In the northern hemisphere these will be the days which have the longest and shortest time between sunrise and sunset, and would have been recognised by our distant ancestors as the days when the midday sun was at it's annual highest or lowest above the horizon..

However, as previously mentioned, although the day with the least daylight in the northern hemisphere occurs on 21st Dec (hence it defining the winter solstice), this is not the date of the latest sunrise or the earliest sunset. In the time the earth rotates through 360 degrees on its axis it also travels around the sun in its orbit. Given that there are 365 days in a year and 360 degrees in a circle, the earth has to rotate approximately 361 degrees before the same face is precisely orientated toward the sun. If the earth's speed around the sun was constant there would be no problem, but it isn't. Because the earth's orbit is slightly elliptical, when the earth is at it's closest to the sun which occurs in December (Perihelion) it travels faster in its orbit than when it is at it's furthest (Aphelion). When it travels fastest (and therefore further along its orbit in the time it takes to complete one 360 degree rotation), the earth has to rotate slightly more to present the same face to the sun in December than it does in June.

This is why the earliest sunset occurs around 14th Dec and the latest sunrise occurs around 1st January (it is not precisely the same each year - don't mention the celestial mechanics of leap years or the "precession of the equinoxes"!). However, the shortest hours of daylight (i.e. the shortest time between sunrise and sunset) will still, by definition, be on the winter solstice on 21st Dec. If you think that this all sounds very pedantic, and an exercise in semantics, you would be right. but it is an interesting point of discussion and it's nice to understand the workings of the world around you! :lol:

Just had a look here for Aberdeen. It does as you say except latest sunrise is nearer to 28 Dec (middle of the 8.48 range).
Shortest day is Dec 22. Latest sunrise is same from 25 Dec to Jan 1 is 8.48 (to nearest minute). Earliest sunset is 3.35 on 14, 15, Dec, which surprised me!

 

[Jake]

But it's nice to think that ultimately, it will be light at 8:0am......

Who cares about that! (Well, you do obviously.) But it will be nice when it's light getting out of work.

 

[dickm]

Thanks for the link, Jacob - glad to know that it's not just imagination that it was still getting light later in the morning.

While I was still working, always found it frustrating round about the time that it started getting light at homecoming - there was a period of about a month when it was light enough to see all the jobs that needed doing in the garden, but not enough daylight time to do them!