Posted on 09 January 2012 at 11:32h

First day back at school and having to get used to getting up in the dark again. Thankfully this doesn't last forever as the days get longer at an ever increasing rate so soon we'll be getting more sun than you Southerners. A couple of weeks a go I saw a comment on facebook related to the apparent fact that soon after the shortest day on December 22nd the mornings don't get any later at all it's only the sunset that gets later, the sunrise actually doesn't start getting earlier than the shortest day until January 4th. You can see all the details here time and date .com

I put January and February into excel and plotted the sunrise and sunset and you can see it's not symmetric. The reason for this is the difference between the solar time and the clock time. Solar time is based on the position of the sun but because the sun moves in an elipse it moves slower when it is far from the sun that when it is close (conservation of energy). Clocks tick regularly so as the earth speeds up the solar clock ticks faster but slower when the earth slows down. So this makes the time of day when the sun is at its highest slightly different each day. Today's clocks are based on a standard second but many years ago they were based on the movement of the earth around the sun however since the speed changes the time had to be adjusted using the equation of time. Quite interesting.