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Solstice factlet
Posted: Sun Dec 22, 2019 11:44 am
by Tessa K
Interesting factlet:
Even though today is the shortest day and the days now get longer, sunrise carries on getting later until January 6 - Twelfth Night.
Re: Solstice factlet
Posted: Sun Dec 22, 2019 12:35 pm
by Pucksoppet
Tessa K wrote: ↑Sun Dec 22, 2019 11:44 am
Interesting factlet:
Even though today is the shortest day and the days now get longer, sunrise carries on getting later until January 6 - Twelfth Night.
Understanding why that is is an interesting exercise. For some.
Re: Solstice factlet
Posted: Sun Dec 22, 2019 1:18 pm
by dyqik
Tessa K wrote: ↑Sun Dec 22, 2019 11:44 am
Interesting factlet:
Even though today is the shortest day and the days now get longer, sunrise carries on getting later until January 6 - Twelfth Night.
This isn't correct for the UK.
The latest sunrise and earliest sunset times vary by latitude.
January 6th is about right for somewhere around DC's latitude. The latest sunrise for London looks to be around Dec 29th.
Re: Solstice factlet
Posted: Sun Dec 22, 2019 1:23 pm
by basementer
Tessa K wrote: ↑Sun Dec 22, 2019 11:44 am
Interesting factlet:
Even though today is the shortest day and the days now get longer, sunrise carries on getting later until January 6 - Twelfth Night.
If we lived on a planet that had a perfectly circular orbit, that would take out one of the terms in the relevant equations. If we lived on one whose axis of rotation were at 90 degrees to the plane of its orbit, that would take out another.
The latter term governs day length and it pushes dawn earlier and dusk later, or vice versa, in a nicely symmetrical way. But around the solstices, its max and min, its rate of change is near zero and so the other term becomes not just noticeable but dominant. The Earth is currently heading for its closest approach to the Sun and travelling faster, which is pushing both sunrise and sunset later in both hemispheres.
Re: Solstice factlet
Posted: Sun Dec 22, 2019 4:45 pm
by Tessa K
dyqik wrote: ↑Sun Dec 22, 2019 1:18 pm
Tessa K wrote: ↑Sun Dec 22, 2019 11:44 am
Interesting factlet:
Even though today is the shortest day and the days now get longer, sunrise carries on getting later until January 6 - Twelfth Night.
This isn't correct for the UK.
The latest sunrise and earliest sunset times vary by latitude.
January 6th is about right for somewhere around DC's latitude. The latest sunrise for London looks to be around Dec 29th.
According to
this for December and
this for January, it's right for me in London. In fact, although sunrise starts getting earlier on January 6 it's not until January 11 that it's earlier than today.
Re: Solstice factlet
Posted: Sun Dec 22, 2019 5:01 pm
by dyqik
According to
NOAA (which shows its working, but doesn't give fractions of a minute), and your links, sunrise is 8:06am in London on Dec 26th to Jan 5th ish, but 8:05am on Jan 6th. That puts the latest sunrise in the middle of Dec 26th to Jan 5th, or about New Year's Eve/Day in London.
Re: Solstice factlet
Posted: Sun Dec 22, 2019 5:09 pm
by Tessa K
dyqik wrote: ↑Sun Dec 22, 2019 5:01 pm
According to
NOAA (which shows its working, but doesn't give fractions of a minute), and your links, sunrise is 8:06am in London on Dec 26th to Jan 5th ish, but 8:05am on Jan 6th. That puts the latest sunrise in the middle of Dec 26th to Jan 5th, or about New Year's Eve/Day in London.
I was going by the fact that it's 8:06 on the 5th and 8:05 on the 6th but I accept there may be a difference of seconds not accounted for. But it is still not until the 11th that it's earlier than today. So I am a tiny bit right. I'll cling to that ...