Few Universal Constants Used In Most Physics Equations
All constants are derived from the nature of mass-energy. For instance, the concept of light speed hinges on the constant speed of ‘pure massless energy’ in a vacuum. The reduced Planck constant rests on the smallest movements of energy. The gravitational constant represents the constant force between two bodies due to their mass-energy. The same generally applies to the other physical constants, but we won’t go into the explanation of each constant here.
Visible light is a certain frequency of electromagnetic radiation. Mass-energy refers to a fundamental measurable property of electromagnetic force and the other forces. Thus, the speed of light (and the other constants, for their own reasons) are ‘derived from the nature of mass-energy’.
Constants can be used to give us natural units, we can use natural units as a measuring stick of sorts. This is useful because time and space are relative to frame of reference, and that can make measuring things tricky.
The Universal Constants
There are only a few universal constants used in most physics equations a non-physicist will encounter: the speed of light c, Planck’s constant h (and the related reduced Planck constant h), and Newton’s gravitational constant G.
The physical constants are measurable properties of the physical universe that don’t change, everything else is relative to these constants.
Below are some of the more important universal constants in the physical universe: Light speed constant, the Planck constant, and the Gravitational Constant.
- Light speed ‘c’ is the constant, and only the speed light (pure energy) can travel in a vacuum. Light speed is the max speed of the universe.
- The reduced Planck constant ‘h’ is the smallest unit of measurement energy can quantize to and is based on Planck’s constant ‘h’. The Planck length, based on this unit, is the shortest distance energy can travel. The reduced Planck unit is the minimum unit of measurement in the universe.
- The gravitational constant (capital ‘G’) is the constant gravitational force between two bodies (this should not be confused with earth’s local gravity, express as small ‘g’).
There are also conceptual constants that are important to physics such as the construct spacetime which is a theoretical combination of space and time. Space and time are relative, but spacetime is constant. Also important to physics, an inertial reference frame can be considered a sort of constant.
There are also a set of constants what are “dimensionless” physical constants. This just means a constant not based on a human-created unit (like Pi). Light speed may be constant, but we are creating a unit around it, something like Pi (which is “a ratio”) works regardless of what system of units we are using.
Most of the non-dimensionless constants need to be the exact value or the universe breaks, however dimensionless physical constants (explained typically in values of Planck units for the sake of communication) represent values that simply aren’t dependent on human created units (like Pi).
All the fundamental dimensionless constants are derived from “the mass of quantum particles”, and explained with the human-defined Planck, so just like the universal constants, the dimensionless constants are also derived from, and explained, by the nature of mass-energy.
Everything we know about the universe is based on laws of physics which we assume to be constant and unchanging. But are they? Astrophysicists are looking at the universal constants that underlie the laws of physics to see if they may have changed over the course of the universe’s history. Most of these constants, such as the speed of light, are almost impossible to measure for change, because all of our other measurements are based on them.
But others, like the lesser known fine structure constant, may be possible to measure for change. This constant, known as alpha, characterizes the ‘strength of the electromagnetic interaction between elementary charged particles’. Because we can measure alpha through spectrographs, it’s possible to look at the spectrographs of gasses that ancient, distant quasars have hit at different periods of time and to if alpha has changed.
The answer? We don’t know. Some studies have shown a slight change in alpha over time, while others haven’t. If alpha has changed over time, that could give us essential clues into whether the current grand unified theories of physics are valid.