 fraction to approximate the measurement value and to match the superior epoch.</p><p>In our current system, astronomical constants are classified as the defining constants, primary constants and derived constants. An example of a defining constant is the speed of light, which is defined as 299792458 m/s. Primary constants are determined by observations. An example is Earth's equatorial radius. Derived constants are obtained by combining the primary constants or defining constants or both. An example is the