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Wednesday, November 27, 2019

What Time Is It On the North Pole, South Pole, Moon?

     First off, as I write this, at the South Pole it is 30 below zero with more sun than clouds and the sun is up all day. The time is a different story. Bases and stations in Antarctica tend to keep either the time relating to their home territory or the supply line that feeds them. 
     Officially Antarctica Standard Time is Greenwich Mean Time (GMT). Greenwich Mean Time is clock time at the Royal Observatory in Greenwich, London and it is the same all year round and is not affected by Summer Time, or as it is also known, Daylight Saving Time. 
     When the sun is at its highest point exactly above the Prime Meridian, it is 1200 noon at Greenwich. GMT is also a time zone, used by Great Britain and Northern Ireland when Daylight Saving Time is not in use, from October to March. 
     Until 1972, Greenwich Mean Time (also known as Zulu time) was the same as Universal Time (UT). Since then, GMT is no longer a time standard. Today, Greenwich Mean Time (GMT) is only the name of a time zone that is used by a few countries in Africa and Western Europe, including the UK during winter and all year in Iceland. 
     The Greenwich Meridian (Prime Meridian or Longitude Zero degrees) marks the starting point of every Time Zone. Every 15 degrees of longitude represents one hour's difference in time. 
     Another time...Coordinated Universal Time (abbreviated UTC). UTC is the time standard commonly used across the world and the name Coordinated Universal Time is used. 
     Two components are used to determine UTC: The International Atomic Time (TAI) which is a time scale that combines the output of some 400 highly precise atomic clocks worldwide, and provides the exact speed for our clocks to tick. The other is Universal Time (UT1), also known as astronomical time or solar time. 
     Strictly speaking the South Pole operates GMT but you can walk through all 24 time zones in a few seconds. In practice, polar explorers and scientists there simply choose whatever time zone is most convenient. Those working at McMurdo Station in Antarctica, for example, have chosen to use New Zealand local time.
     Here’s a quirky fact...electric clocks are usually wrong. It has something to do with the generators running at 60.1 hertz that makes the clocks run fast. So every couple of days, they have to go around and set them back 5 minutes or so. 
     What about the North Pole? At the North Pole, where the sun also rises and sets only once per year, all lines of longitude meet and hence all time zones converge. There is no permanent human presence at the North Pole and no particular time zone has been assigned. 
     And, while we are on the subject of time, what time is it on the Moon? If were to ask a scientist about it, they would explain the complications of Einstein’s Special Relativity, but ignoring that, it’s the same time as it is on Earth, but what’s that mean? 
     Here on Earth time is defined by the motion of the Sun in the sky so the local time depends on where you are on Earth. i.e. what time zone you’re in.
     There exists a similar time system based on the motion of the Sun as seen from the Moon that’s known as Lunar Standard Time, but almost nobody cares about that. 
     So, if you were talking to an astronaut on the moon and asked him what time it was, what would he say? It goes back to that time that doesn’t vary with location…UTC. 
     The time on the Moon is the same as the UTC time on earth. But for the most part time is based on local time of the astronaut’s blast off point. Some mission constraints require that the sun be at an elevation of a specified number degrees above the horizon during the mission, so the actual time is irrelevant.

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