|
Understanding Star Time (LST) |
We all know that the earth is spinning in space. And that relative to the Sun it rotates once every 24hrs. We also all understand that the earth ORBITS the Sun once every year. (364,25 days to be exact.) Now, because of that ORBIT around the sun, our spinning on our own axis – relative to the STARS, is not quite 24hrs. It is in fact 23hrs and 56 minutes (near enough) This, if you like is, the Star Clock. Normally we measure time by the Earth’s rotation relative to the Sun. When the Sun is directly overhead at Greenwich, London, we call that “Mid-day” – 12.00 pm GMT or Noon. GMT is Greenwich Mean Time. Now also called UTC (Universal Time Coordinate) In order to decide when one day ends and the next begins we have established an “International Dateline” which runs more or less vertically from South Pole to North Pole just east of New Zealand, Fiji and the east-most tip of Russia. Diametrically opposite this (round the other side of the earth) it is 12.00 noon above Greenwich, London, UK. With LST, we are NOT measuring time by the Sun, but by the Earths rotation relative to the stars. So a Stella or Star Day is 23hrs 56 mins long. And that’s it – simple really. For convenience we have split the world up into 1 hour length time zones and this is what gives rise to some confusion when it comes to a WAVE moving smoothly around the earth. (The time zones follow borders and do not keep to an exact 15 degree or 1 hour band.) THE WAVE Imagine a line running from the North Pole to the South Pole, in this case aligned with the Milky Way. As the earth spins that line moves across the surface of the earth, from east to west. As the line moves across each time zone it enters in the east and, one hour (or so) later, exits at the west. For example, as the line moves across South Africa if it crosses Johannesburg at 01.46am then it only reaches Capetown at 02.21am. THIS is the time we are looking for when we are planning to do a synchronized wave. When calculating a Local time for a “wave” we have to use tables. There are tables for GMT (UTC) and there are tables for LST (Local Star Time) CALCULATING YOUR LOCAL TIME for the given Star Time of 13.30 LST Three easy steps: 1. Find your time zone
here. For example, South Africa is +2. (We are 2 hours ahead of
Greenwich mean time) (We don’t change our clocks for the summer so we are
always GMT + 2. But because London Does change it’s clocks for the summer
by 1 hour, some of the year we are only 1 hour ahead or their Local time.) |