Fundamental physical constants are the unchanging quantities that form the foundation of our physical laws. They dictate the architecture of reality, from the strength of gravity to the stability of atoms.

Dimensional vs. Dimensionless Constants Physicists categorize these constants into two distinct types:

• Dimensioned constants (like the speed of light, $c$, or the gravitational constant, $G$) have units. Their numerical values are effectively human artifacts because they depend entirely on our chosen measurement systems, such as meters or seconds.
• Dimensionless constants are pure numbers that remain identical regardless of the unit system used. The most famous is the fine-structure constant ($\alpha \approx 1/137.036$), which dictates the strength of electromagnetic interactions. Many physicists argue that only dimensio ...