Standards - Changes in Metric Definitions (2)

2. Meter Original Definition: One ten-millionth of the distance from the North Pole to the Equator along the meridian passing through Paris. Current Definition: The distance light travels in a vacuum in 1/299,792,458 of a second. Reason for Change: Errors in measurement results, minute changes in the standard prototype. 3. Kilogram Original Definition: The weight of one liter of water at 4 degrees Celsius. Current Definition: Redefined based on the Planck constant. Reason for Change: Can vary depending on pressure conditions. Minute changes in the standard prototype. 4. Ampere Original Definition: Defined based on the force applied between two conductors separated by one meter in a vacuum. Current Definition: Redefined based on the elementary charge of an electron. Reason for Change: Difficulty in implementation. 5. Kelvin (Celsius temperature + 273.15) Absolute zero became -273.15 degrees Celsius by calculating the point where molecular motion ceases according to Charles's Law. Original Definition: 1/100th based on the melting point (0) and boiling point (100) of water. Second Definition: Based on the triple point of water. Current Definition: Redefined based on the Boltzmann constant. Reason for Change: Varies depending on isotopic composition.