Stephen's review
Calendar: Humanity's Epic Struggle To Determine A True And Accurate Year
by David Ewing Duncan
Actually, I disagree with your premise about how the current nuclear clocks fail to take into account the declining speed of the Earth's rotation. That is not a function of the clocks. Rather, the failure is in relating the declining rotational velocity to a celestial object. Therefore, the clocks measure duration and the relational function of pinning the duration of time to an Earth Reference Model, called astrometry, is where the error lies. There is a great need to update the star catalog of the quasars used to define what time it is as the current catalog was created about 18 years ago and since then we have endured milliarcseconds of drift which in turn create uncertainty as time relates to our experience of duration. All of which (drift, more accurate measuring of duration and slowing rotational velocity) leads to the insertion of leap seconds on an almost annual basis. This can effect many things like the use of GPS navigation systems, the internet, cell phones and satellite systems. Thanks for listening. Jeff
Hi Jeff, thanks for explaining/clarifying that. I read this book several years ago now and I was just writing offhand about something that I remember reading bout back then. I'm a general reader with more knowledge of the history than the science. I'm not sure how well this issue is explained in the book Calendar, but my incorrect comments should not be taken as a reflection of the author's actual explanation, which may be perfect. Thanks, Steve.
Steve, No worries. I am an afficionado of space and work in the field so this kind of stuff is right up my alley. Hope all is well in Canada. Yours, Jeff.
Stephen's review
Calendar: Humanity's Epic Struggle To Determine A True And Accurate Year by David Ewing Duncan
Stephen's review
rating:
This was a well written account of the long struggle to create an accurate ongoing calendar of days. This task was much more difficult than I ever imagined. consider: do you use the moon as your base? The Sun? All the obvious ways of calculating the number of days in a year are inaccurate. A great irony is that the latest nuclear clocks are actually too precise because they fail to take into account the declining speed of the earth's rotation.
Actually, I disagree with your premise about how the current nuclear clocks fail to take into account the declining speed of the Earth's rotation. That is not a function of the clocks. Rather, the failure is in relating the declining rotational velocity to a celestial object. Therefore, the clocks measure duration and the relational function of pinning the duration of time to an Earth Reference Model, called astrometry, is where the error lies. There is a great need to update the star catalog of the quasars used to define what time it is as the current catalog was created about 18 years ago and since then we have endured milliarcseconds of drift which in turn create uncertainty as time relates to our experience of duration. All of which (drift, more accurate measuring of duration and slowing rotational velocity) leads to the insertion of leap seconds on an almost annual basis. This can effect many things like the use of GPS navigation systems, the internet, cell phones and satellite systems. Thanks for listening. Jeff
Hi Jeff, thanks for explaining/clarifying that. I read this book several years ago now and I was just writing offhand about something that I remember reading bout back then. I'm a general reader with more knowledge of the history than the science. I'm not sure how well this issue is explained in the book Calendar, but my incorrect comments should not be taken as a reflection of the author's actual explanation, which may be perfect. Thanks, Steve.
Steve, No worries. I am an afficionado of space and work in the field so this kind of stuff is right up my alley. Hope all is well in Canada. Yours, Jeff.