I have updated my proposal for extending UTC to dates before 1972. The principal changes are the removal of the section on NTP and a somewhat hand-waving justification for using atomic time before the invention of the atomic clock. I have also addressed the other feedback provided here by going into more detail about the meaning of table 1, acknowledging UTC before 1972, and proposing a name for the time scale.
I am requesting additional feedback on the revised paper. Here is the justification for using atomic time prior to the invention of atomic clocks: ``For a time scale to be useful for measuring events, it must be based on some physical property that can be measured. UTC is based on the SI second, which is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom when it is at rest with respect to the Earth, at a temperature of 0 degrees Kelvin, and located at mean sea level. These measurements are made continuously by national laboratories around the world. The data is sent to the International Bureau of Weights and Measures, which combines the information and disseminates International Atomic Time, upon which UTC is based. ``A time scale used for scientific measurements must be rigorously defined and robustly measured, as International Atomic Time is. If we try to extend this definition backward into ancient times, we run into the problem that there were no atomic clocks before 1955, and therefore nobody was measuring the SI second as it is presently defined. ``However, when describing ancient events, we do not need to actually measure time, we can instead imagine that we are measuring it. For example, we say that the Big Bang that marked the start of the Universe took place 13.8 billion years ago. In this context, ``years'' does not refer to the number of times that the Earth has gone around the Sun since the Big Bang, because the solar system has only been in existence for the last 4.54 billion years. Instead, we take the present duration of a year and project it back in time, thus imagining that we are measuring time using the year as it presently exists. ``Similarly, we can imagine that atomic clocks have been measuring time for the last 3,000 years, and use that as our time scale. This imaginary time scale does not have the precision of International Atomic Time, since there were not, in fact, atomic clocks 3,000 years ago, but it is sufficient for our limited purpose.'' Thank you, John Sauter ([email protected]) -- PGP fingerprint = E24A D25B E5FE 4914 A603 49EC 7030 3EA1 9A0B 511E
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