# Lengthening days, but by how much?

Discussion in 'Bushcraft and survival skills' started by oldtimer, Jan 2, 2019.

1. ### oldtimer Full Member

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Our recent various rites, rituals and sacrifices have succeeded in lengthening the days and shortening the nights, but by how much?

SWMBO asked me yesterday how much longer each day is until we get to midsummer and I realised that not only did I not know the answer but didn't know either how to work it out or even where to go for information. The builders of Stonehenge would have fired back the answer in a jiffy and SWMBO was quite surprised that there was something I didn't know. This must have been a shock to her as she is always telling me that I know it all.

She has already worked out that by checking the sunrise and sunset daily on her smartphone over the coming week she can find the answer. Can you help me beat her to it so I can re-assume my mantle of omniscience?

#1
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I think it depends on where you are and also when ( day of year) .
The closer to Equator, the less lengthening/shortening. I know that for a fact. Not so sure about how close to the soltices influences it though. If it does.
Logically it should not, as the Earths moving is a constant, fluid motion?

#2

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If the increase is constant, Just take the number of daylight minutes at the longest day, minus the number of daylight minutes at the shortest day, then divide with number of days between those..
Then you get the number a minutes change each day.

(or something like that? )

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4. ### Tengu Full Member

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Well, thank you for doing all that; I was getting quite weary of rising BEFORE sparrows fart to get to Uni.

As a promoter of Classical Civilisation I have a big brass machine of cogs and gears that can give you the answer...No astrologer needed.

You get a slave to turn the handle and the answer comes up in a window. Truly `deus ex machina`.

<looks around>

But I cant seem to find my slave to do it at the moment. Sorry about that.

#4
5. ### Mesquite Anyone for sailing?

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The simple answer for you OT is you gain or loose approximately two minutes of light a day between the solstices

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6. ### Chainsaw Native

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Stick your town and here in be prepared to drink from the fire hose as our american cousins would say (more info than you can swallow)

https://www.timeanddate.com/sun/uk

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That is a really cool site!
Thanks!

#7

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Less when he is at his Chateau in the Pyrenees watching the sunset with a bottle of wine in his hand, , more when he goes bird watching to the Shetlands!

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9. ### Broch Full Member

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The actual change follows a sinusoidal curve - so there is virtually no change in December then maximum change around the 21st March (I believe 2.8 minutes?) then no change again in late June. If you plot a sinusoidal curve with daylight hours against day of the year for wherever you are in the world it is reasonably straight forward to work out a) how many daylight hours there are in a particular day and, b), (by calculating the gradient) the rate of change of daylight hours on a day -

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10. ### bobnewboy Settler

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I just use the BBC Weather app on my phone. The forecast is location based and includes the sunrise and sunset times.

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11. ### Robson Valley Full Member

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Our days lengthen in the afternoons faster than they do as earlier sunrises.
The change is not linear any where, but can be plotted as a 2 lobed "annalemma" = the equation of time.
You actually should carve one to act as the gnomon for a serious sun dial if accuracy matters.

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12. ### Broch Full Member

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They do before the 21st March but then they lengthen faster in the morning than in the afternoon up to the summer solstice at which point the afternoons get shorter faster until September when the morning get shorter more rapidly

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13. ### Robson Valley Full Member

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I see that as the lop-sided annalemma.
Maybe by Jan 15, I notice the afternoons lengthening.
Mid Jan to mid March can be coldest of all (-30C does wrinkle your nose.).
Nothing seems quite so bad in daylight. Leaving work in daylight of an evening is an annual thrill.

Today is big S wind and +1C. What's called the "Pineapple Express."
An air stream which starts in the region of Hawaii. A day closer to spring
but hellish driving in the 12" wet snow we got.

#13

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Winter sucks here too. Around 10 hours of daylight only. I only get one hour of light after I come home from work to work in the garden.....
Pool is a tad to cool too. Have been thinking of designing a sun heating system for it though.

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15. ### Broch Full Member

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Here you go - a bit of an approximation but good enough for estimating in the UK:

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16. ### Robson Valley Full Member

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I'm at 53N so the day length swings are substantial enough to use black-out curtains in the bedroom windows in the summer.
I have seen shade air temps from -35C up to +47C at my house.
The west side of the house is entirely covered with grape vines for substantial relief in the summer.
That's 40' long, 14' high and 2' out from the house wall. Best ever was 35 lbs per vine.

I have family in Dawson City, YT who get a month+ for daytime and a month+ of winter night time.
Big celebration when the sun clears the horizon each spring!

#16

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Weird how so many things operate according to a Gauss looking curve....

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18. ### Broch Full Member

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Not really; it's circular motion

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But graphically it is a Gauss curve?

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