Sunrise today

[fian]

Pardon me if this has been said... a little known cheering astronomical fact: the earliest sunset is on the 13-14th December. Its getting lighter in the evenings already.

In Galician proverbs, it includes that statement, although it is particularized to the fact that it also coincides with being the shortest day of the year. "For Santa Lucia (13) is the biggest night of the day"

 

[JamezF]

Anybody have an explanation why the day starts lengthening at sunset first?

My understanding is that it's a combination of the effects of the Earth's axis being tilted with respect to the plane of its orbit about the Sun, the orbit being slightly elliptical and that the Earth is itself rotating whilst orbiting the Sun. I think it's quite tricky to visualise though. The BBC have a fair crack at explaining it here:

Why do mornings still get darker after the winter solstice?

One of the consequences of this combination of motions is that if you take a photo facing the Sun regularly at the same time of day (GMT) over the course of a year and overlay them all, you get an image that shows how the apparent position of the Sun changes. It's called an Analemma:

[Jfishburn at English Wikipedia, CC BY-SA 3.0, via Wikimedia Commons]

How tilted the path is depends on your location. At the equator it would be horizontal. The Sun reaches the extreme ends of the shape at the solstices. I've been wanting to set up a camera to do this at home for ages, but always seem to have more urgent things to do

Some more complex sundials are marked up to take account of this apparent motion, where it's called the Equation of Time (yeah, making my own sundial is something I want to do one day, too ) and it used to be necessary to take it into account when accurately calculating a ship's position at sea from the Sun.

James

 

[fian]

Regarding the period of Persephone, either in its agricultural version (period without planting/pruning period) or temporary (less than 10 hours a day) for the Atlantic/Celtic arc, it ranges from the beginning of November to the beginning of February. In Galicia from November 8 to February 3, this last date that the proverb includes in its version "Por San Blas (3), an hour and a half more".

 

[user 20297]

Although we call a day, twenty-four hours, the time actually taken for one rotation of the Earth varies throughout the year. At this time of year the true length of one day is always less than twenty-four hours. But we don't micro-adjust our clocks to account for this variance and the slight lack of synchronicity is the result of this.

 

[Erichalfbee]

Although we call a day, twenty-four hours, the time actually taken for one rotation of the Earth varies throughout the year. At this time of year the true length of one day is always less than twenty-four hours. But we don't micro-adjust our clocks to account for this variance and the slight lack of synchronicity is the result of this.

Too true
I don't even get up at the same time every day either

 

[jenkinsbrynmair]

Too true
I don't even get up at the same time every day either

for years I've got up with the sun (something to do with sleeping in cabins with no scuttles for years maybe - although now, not even blackout curtains help) so at least it's now nice to have a lie in until 0830

 

[Rob H]

Nor me. And more's the pity, really. There's a lot of interesting information that could be learned instead of the drivel that some people choose to believe instead, and that's not even starting on the ones who think that the Sun isn't a star, or don't understand that there is no "dark side of the Moon" or think that somehow the Moon isn't all there when you can only see half of it.

And then there's just the gobsmacking stuff like looking at the Moon (I think it's even more effective when using a decent size telescope) and knowing that men have walked around on it and come back, even if very few of them are still alive. Or finding Mars in the night sky (as you can in the early part of the night at the moment) and being aware that we have actually landed robotic explorers there.

James

On this point (and not bee keeping) your incorrect, there is a "Dark Side of The Moon" a great Album from Pink Floyd - early 70's. Sorry to be pedantic but its not often on here I can compete!

 

[JamezF]

On this point (and not bee keeping) your incorrect, there is a "Dark Side of The Moon" a great Album from Pink Floyd - early 70's. Sorry to be pedantic but its not often on here I can compete!

By way of a seasonal reply, "Yonder pedant, who is he?"

I can't deny that it hadn't crossed my mind that someone might point this out. Were I to turn pedant mode up to eleven I might point out that "Dark Side of The Moon" is not the same as "dark side of the Moon", but I've had a busy day outside in the rain and I can't be bothered to stir the pot further

Can't deny that the Pink Floyd album is an outstanding piece of work though, particularly "The Great Gig In The Sky". As was their next one, "Wish You Were Here". Both get played regularly at home, even by my teenage son, though he seems to be going through a bit of a Blue Öyster Cult phase at the moment.

James

 

[Rob H]

By way of a seasonal reply, "Yonder pedant, who is he?"

I can't deny that it hadn't crossed my mind that someone might point this out. Were I to turn pedant mode up to eleven I might point out that "Dark Side of The Moon" is not the same as "dark side of the Moon", but I've had a busy day outside in the rain and I can't be bothered to stir the pot further

Can't deny that the Pink Floyd album is an outstanding piece of work though, particularly "The Great Gig In The Sky". As was their next one, "Wish You Were Here". Both get played regularly at home, even by my teenage son, though he seems to be going through a bit of a Blue Öyster Cult phase at the moment.

James

I can't come back from that one!

 

[richardh]

Same as the rest of us, perhaps ... difficulty getting out of bed in winter? ;-)