Final answer:
The constancy of gi and g* over time is based on assumptions within specific disciplines such as physics, where constants like the Hubble constant or gravitational acceleration g are considered invariant under certain conditions and in economics, where labor supply and price levels in a base year are assumed to be constant for ease of analysis.
Step-by-step explanation:
When assessing the constancy of gi or g* over time, several assumptions may be made depending on the context of the variables mentioned. In general, these conditions for constancy relate to theories and concepts in physics where certain values are assumed to remain constant under specific circumstances.
For instance, in cosmology, assuming the Hubble constant is unchanging implies that the rate of the universe's expansion is constant. This simplifies calculations but does not take into account factors such as potential slowing down of the expansion rate. Similarly, in gravitational physics, the value of g, or acceleration due to gravity, is usually considered constant near the Earth's surface for practical applications, but this assumption does not hold over large distances where g changes with altitude.
In economics, a constant labor supply curve in the short run assumes that the average hours people are willing to work at a given wage, and other factors like age structure of the labor force and labor market regulations, remain unchanged. In the calculation of real GDP, the use of a base year establishes a period in which prices are deemed constant to facilitate comparison over different years.
Lastly, in population genetics, the assumption of genetic equilibrium implies that generational gene pools remain constant when there are no evolutionary pressures acting on them. This assumption is critical for certain theoretical models that describe population genetics.