Q.Having all units in atomic standards is more useful. Explain.

Step 1. A standard based on a physical prototype -- like the historical platinum-iridium kilogram cylinder kept in Paris -- has real drawbacks: it is a single, one-of-a-kind object that could be damaged, contaminated, or lost, and every other mass standard in the world has to be compared back to that one physical object.

Step 2. An atomic standard, by contrast, is based on a property of atoms (like the specific radiation frequency of Cesium-133 that defines the second) that is identical for every atom of that element, everywhere in the universe.

Step 3. This means an atomic standard can be independently reproduced, with the same precision, in any suitably equipped laboratory anywhere -- there is no need to travel to, or compare against, one single physical reference object.

Step 4. Atomic standards are also extremely stable over time -- they do not wear, corrode, or drift the way a mechanical or physical artifact can -- which is why the Cesium atomic clock is accurate to about three-millionths of a second per year. …

Compare the reproducibility, universality, and stability of atomic standards against phy …

• Only mentioning precision, and missing the equally important points of universal reproducibility and long-term stability. …