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Asked by nvademo to Asif, Laura, Lena, Sean, Viv on 16 Mar 2012.
Question: There is a theory that every 100 years we gain 12 seconds; is this true?
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Sean Murphy answered on 16 Mar 2012:
Yes.
Scientists are deciding whether or not to eliminate “leap seconds” from Coordinated Universal Time (UTC). People are aware of leap years, which add an extra day ( at the end of February) every four years in order to adjust for the extra part of the day in Earth’s yearly rotation around the sun. But leap seconds serve a much less purpose: by adding a second to the clock in for slight, unpredictable changes in the Earth’s rotation, caused by things like the gradual slowing of Earth’s rotation caused by the friction of ocean tides or the gravitational pull of the moon. In simple terms, every now and then we have to stop the clock for a second, so the Earth’s rotation can catch up to our measurement of time.
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Lena Ciric answered on 17 Mar 2012:
I’m not exactly sure about the number of seconds that we gain each 100 years, but our days (the time it takes for the Earth to spin around it’s axis) are definitely getting longer. The reason for this is because the Moon is slowly moving further away from us. The Moon’s gravity acts on the Earth by causing tides. The movement of the tides around the Earth put a spin on our own daily rotation. As the Moon moves further away, the gravity causing the tides will reduce and the extra spin put on the Earth will also decrease which means our days will get longer.
Comments
ogoldfinch09 commented on :
Stopping clocks for one second seems a little pedantic, is it really necessary?
Sean commented on :
I think the problems the “leap seconds” are causing at the moment are due to the fact that the clocks that GPS run on end up differing to the clocks we use down on earth.