Proton-to-electron mass ratio

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Numbers

$\mu$:

1836.152673426 +/- 1.60e-7

$\mu^{-1}$:

0.0005446170214889 +/- 4.70e-14

Definition

The proton-to-electron mass ratio $\mu$ is the quotient of the rest mass of a proton by the rest mass of an electron.

Comments

(1)

$\mu$ may not be constant [3]. Barrow gives a popular account of dimensionless constants such as $\mu$ [1].

Programs

(P1)

Python

from scipy.constants import physical_constants
physical_constants['proton-electron mass ratio']
physical_constants['electron-proton mass ratio']

References

[1]

John D. Barrow, "The Constants of Nature: From Alpha to Omega -- the Numbers That Encode the Deepest Secrets of the Universe", 2003.

Links

[2]

Wikipedia: Proton-to-electron mass ratio

[3]

Wikipedia: Proton-to-electron mass ratio: Variation over time

[4]

The NIST Reference on Constants, Units, and Uncertainty

[5]

NIST Reference: Standard Uncertainty and Relative Standard Uncertainty

Similar tables

Mass ratios — holds ratios of particle rest masses; $\mu$ and $\mu^{-1}$ appear there as $m_{\rm p}/m_{\rm e}$ and $m_{\rm e}/m_{\rm p}$

Data properties

Entries are of type: real number

Table is complete: yes (it holds the NIST-published ratios $m_{\rm p}/m_{\rm e}$ and $m_{\rm e}/m_{\rm p}$, shown here as $\mu$ and $\mu^{-1}$)

Sources of data: [4] (based on CODATA 2022)

Reliability: The intervals are centred at the NIST CODATA 2022 recommended values [4]; each radius is five times the standard uncertainty published there, with the parenthesized concise form interpreted as in [5].

How well the digits are known: measured

How they were obtained:

Not computed: the values come from experiment, and each interval is centred at the NIST CODATA 2022 recommended value with radius five standard uncertainties.