Natural Units

An advantage to stating equations in single-dimensional natural units (Planck units) is the ease with which we see the arrangements of physical quantities that conserve universal constants. For example, since

and

we see that

Notice that the product of Compton wavelength and rest mass is conserved; that is, its value remains constant as values of wavelength and mass change indicating an inverse relationship.

Rearranging terms highlights the correlation

The inverse relationship between Compton wavelength and rest mass is so precise that we can produce the Planck constant using CODATA values of electron and muon Compton wavelengths and rest masses to 11 digits.

We can see the correlated, non-dimensional natural quantities that allow us to calculate Compton wavelength and rest mass from the Planck constant; these are the ratios of wavelength and mass to the Planck scale.

The following illustrations are a visually engaging way to help students appreciate the natural structure we don’t see when calculating in arbitrary units. These relationships are revealed in natural units.

Teachers are encouraged to download these images to incorporate into their instruction on natural units and dimensional analysis.


Electric Constant

Conservation

ImageNameFile TypeFile Type

Electrostatic forcePNGPSD

Electric potential energyPNGPSD

Electric potentialPNGPSD

Correlation

ImageNameFile TypeFile Type

Electrostatic forcePNGPSD

Electric potential energyPNGPSD

Electric potentialPNGPSD

Magnetic constant

Conservation

ImageNameFile TypeFile Type

Magnetic forcePNGPSD

Correlation

ImageNameFile TypeFile Type

Magnetic forcePNGPSD

Gravitational constant

Conservation

ImageNameFile TypeFile Type

Schwarzschild RadiusPNGPSD

Escape VelocityPNGPSD

Gravitational accelerationPNGPSD

Gravitational potential energyPNGPSD

Gravitational forcePNGPSD

Correlation

ImageNameFile TypeFile Type

Schwarzschild RadiusPNGPSD

Escape VelocityPNGPSD

Gravitational accelerationPNGPSD

Gravitational potential energyPNGPSD

Gravitational forcePNGPSD

Planck constant

Conservation

ImageNameFile TypeFile Type

deBroglie wavelengthPNGPSD

Correlation

ImageNameFile TypeFile Type

deBroglie wavelengthPNGPSD

Speed of light

Conservation

ImageNameFile TypeFile Type

Photon wavelength and periodPNGPSD

Correlation

ImageNameFile TypeFile Type

Photon wavelength and periodPNGPSD

Planck constant and speed of light

Conservation

ImageNameFile TypeFile Type

Photon wavelength and energyPNGPSD

Compton wavelength & rest massPNGPSD

Correlation

ImageNameFile TypeFile Type

Photon wavelength and energyPNGPSD

Compton wavelength & rest massPNGPSD