NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: what is a second?
From: Frank Reed CT
Date: 2006 May 10, 00:50 -0500
" The consensus seems to be that a second started as an interval within a
mean solar day, but lately has been redefined with reference to the known decay
of radioactive elements. "
Just FYI, Cesium-133 is a stable isotope, not radioactive. The second is
defined in terms of a natural microwave frequency emitted by these atoms. It is
believed to be extremely stable even over the lifetime of the universe. The
choice of Cesium-133 is not necessarily permanent however atomic standards are
likely to be the best choice for a long time to come.
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
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To post to this group, send email to NavList@fer3.com
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From: Frank Reed CT
Date: 2006 May 10, 00:50 -0500
" The consensus seems to be that a second started as an interval within a
mean solar day, but lately has been redefined with reference to the known decay
of radioactive elements. "
Just FYI, Cesium-133 is a stable isotope, not radioactive. The second is
defined in terms of a natural microwave frequency emitted by these atoms. It is
believed to be extremely stable even over the lifetime of the universe. The
choice of Cesium-133 is not necessarily permanent however atomic standards are
likely to be the best choice for a long time to come.
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
