Time Differance Between Greenwich And Different Logitude.

[leigh47]

How is the TIME difference between Greenwich meridian [0 deg.] and another point in the UK ( different longitude west of Greenwich and higher latitude.) calculated? The position being approx. 2deg.25s west. I don't mean time zones, but actual natural time due to rotation of the earth taking 1 day or 24 hours. Hope this is clear!

[=rizla=]

If i understand you then i would have thought 24hrs/360deg * 2deg(25s isnt going to change much)= 0.133 of an hour = 8 mins.

[gen2]

Every 15 degrees = 1 hour so 1 degree = 4 mins and one second of arc = 4 seconds of time.

[Zacs-Master]

A laymans working out:
360 deg in 23 hours, 56 minutes and 4.09 seconds (or 86,164 seconds). So it takes 239 seconds per degree, so roughly 8.62 minutes for 2 deg 25 secs.

[Buenchico]

Simple division is all that is needed. There are 360 degrees of longitude, representing 24 hours of time. So each degree equates to a time difference of 24/360 hours = (24 x 60)/360 minutes = 4 minutes.

2 deg equates to 8 minutes
25 secs of longitude equates to (25/60) x 4 mins = 100/60 minutes = 1 min 40 secs of time

So 2 deg 25 secs equates to a time difference of 9 mins 40 secs.

[Zacs-Master]

Ah yes, I had calculated 25s of arc as 25 secs of time. Schoolboy error.

[ll_billym]

There are many ways to mark the passage of time and what actually constitutes a day.

Seeing as you ask about rotation of the Earth I am guessing that you are asking about the time difference between 'sunrises' (i.e. seeing the same point of the sun) between two points on the Earth on the same day of the year.

If so, then if the latitude is different then there will be a time difference based on this also and this value will change depending on the time of the year. If both places are in the UK then this will be negligible but to take an extreme case at the poles the sun never rises at certain times of year.

[mibn2cweus]

2.00'25" (deg.mmss) =
2 degrees + 0/60 minutes + 25/3600 seconds =
2.0069444...decimal degrees

The Earth turns by one degree in relation to the Sun in (on average)
(24 hours * 60 minutes / 360 degrees) = 4 minutes.

4 * 2.0069444... = 8.02777...minutes
or
8 minutes, 1.666...seconds.

[mibn2cweus]

^ Coincidently, in the time it takes sunlight to reach Earth,
(on average about 8min, 19sec.)
the Earth has turned by almost 2.08 degrees, therefore,
the Sun is no longer where it appears to be.

[BlueToffee]

Not sure I can take all these mathematical calculations at this time in the morning!

[jomifl]

Just to add another layer of complexity, because the earth orbits the sun it has to turn a little more than 360 degrees for the sun to appear to reach the same point (lets say due south or north) each day, so the earth has to turn 360 degrees in 365 days ie about 1 degree further each day. A day therefore take about 4 minutes longer than a complete revolution of the earth with reference to the universe(a sidereal day).

[jomifl]

/the Sun is no longer where it appears to be./
Mibs, nothing is where it appears to be and so nobody is who they appear to be ....confusing innit?

[jomifl]

oops forgot the link;
http://en.wikipedia.org/wiki/Solar_time

[heathfield]

Sunrise time v latitude in the UK...'If both places are in the UK then this will be negligible'. Not really. Midwinter sunrise in London this year is at 08:04, but in Inverness it's not until 08:58 - almost an hour later!

[jomifl]

When I was living in the south of England and doing fieldwork in the west of Scotland miles from the nearest road, calculating the time of sunset especially in the winter was vital.

[ll_billym]

Thanks for pointing that out Heathfield - I vaguely thought it would only be a few minutes when I wrote that!

[mibn2cweus]

The Sun tends to follow a specific longitude when it crosses the meridian at local noon. It's a whole 'nother story for sunrise and sunset.

http://sunrisesunsetmap.com/

[jomifl]

mibs, the sun crosses the lines of longitude, (apparently)

[mibn2cweus]

^ I suppose I could have phrased that more better. ;o)

...the Sun 'crosses' at a specific longitude . . . rather than 'follows'. :o/

[jomifl]

mibs, excellent sunrise/set website. I wish it had existed a few years ago, it would have save me a lot of brain wrangling :o)

[Peter Pedant]

mibs great sunset page thanks ++