Abstract The importance of SI “second” and the role of “coordinate time” in the unification of space-time and other physical quantities are discussed. The relationship between “proper time” and “coordinate time” and the influence of the gravitational field on the “proper time” are illustrated by taking the Schwarzschild field as an example. It is believed that the uncertainty of time unit determines the ones of other physical units. Only the “coordinate time” has a global scope of application, and physical quantities related to large-scale space-time must be and only be characterized in coordinate quantities. The SI “second” is the unit of “proper time”, which is a local physical quantity. To use quantum benchmarks to unify the physical quantities in a large-scale space, it is necessary to further clarify the relationship between “coordinate time” and SI “second”.
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2022, Vol. 43 
