does it gte the same amount lighter every day or does it change, answers on a post card, cheers
J
:-)
2007-01-15 01:55:24 · 13 answers · asked by Anonymous in Science & Mathematics ➔ Earth Sciences & Geology
I am in the UK,
2007-01-15 01:55:45 · update #1
The nearer you are to the longest or shortest day, the slower it changes.
The nearer you are to the equinox (March/September), the faster it changes.
At the moment the days are getting longer (in the UK) by about 2-3 minutes per day. In March it's up around 4 minutes.
2007-01-15 02:59:37 · answer #1 · answered by gvih2g2 5 · 0⤊ 0⤋
The duration of daylight varies as the latitude of the observer and the declination of the sun.
The Polar angle at sunrise (and sunset, the same by symmetry) is found by
Cos(P) = - Tan(LAT)*Tan(DEC)
Because the Earth rotates at 15 degree per hour (solar rate), then divide P by 15 to find the number of hours between sunrise and meridian passage.
Don't forget to multiply the result by 2 (to include the afternoon part) to get the entire length of day.
For a more accurate duration, you'd have to consider the half diameter of the sun (for the whole sun to be below the horizon) and the refraction (the air raises the image of the Sun, making the day a bit longer).
However, for your purpose, it is sufficient to find a value for a given day, then find the corresponding value for the next day. The difference in the daily results corresponds to what you seek (the refraction and half-diameter are the same on both days).
The equation is excellent for someone who lives at a latitude of 45 degrees, as I do: Tan(45) = 1
You can find your latitude from maps, a GPS receiver or from Google Earth.
For your purpose, you can use a declination table found at the web site below.
I will assume that your latitude is 50 N.
Jan.16: declination = -21.1 (21 06 S)
Jan.17: declination = -20.9 (20 54 S)
Jan.16:
Cos(P) = - Tan(50)*Tan(-21.1)
P = 62.622 degrees
2P= 125.244
2P/15 = 8h20m59s
Jan.17:
Cos(P) = - Tan(50)*Tan(-20.9)
P = 62.9295
2P= 125.859
2P/15=8h23m26s
Difference = 2m27s (increasing)
2007-01-15 02:12:21 · answer #2 · answered by Raymond 7 · 1⤊ 0⤋
there are 2 factors
firstly ,how close to the solstice it is.
The closer to the solstice, the change from day to day is the least. The closer to the equinox, the greater the change in day length from day to day.
The second factor is latitude.
The closer to the poles, the greater the change in day length from day to day.
So if you really want to see a difference in day length, spend a fortnight in the arctic circle, a week each side of the equinox.
2007-01-15 04:10:56 · answer #3 · answered by rosie recipe 7 · 0⤊ 0⤋
it varies by a couple of minutes each day, some diaries and calendars have the daily sunset/sunrise times printed in them. Can't wait until the clocks go forward...
2007-01-15 02:02:47 · answer #4 · answered by S B 2 · 0⤊ 0⤋
it gets lighter or the days get longer by 2 minuets a day.
2007-01-15 07:18:34 · answer #5 · answered by dottydog 4 · 0⤊ 0⤋
About two minutes per day
2007-01-15 02:04:21 · answer #6 · answered by Anonymous · 0⤊ 0⤋
It changes every day and depends on your latitude. You can go to the us naval observatory site and lok it up for your location.
2007-01-15 02:02:28 · answer #7 · answered by Gene 7 · 0⤊ 0⤋
roughly 3 minutes per day
2007-01-15 01:58:30 · answer #8 · answered by JOHN 3 · 0⤊ 0⤋
It changes
2007-01-15 01:59:32 · answer #9 · answered by Anonymous · 0⤊ 0⤋
1-1.5mins a day
2007-01-15 02:02:00 · answer #10 · answered by Anonymous · 0⤊ 0⤋