Physical constant
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A physical constant is a size, something that has been measured, which has a special meaning for physics. For example, Physical constants are different from mathematical constants because they are not just numbers but are numbers and a unit of measurement together, and because people find them not by calculating but by measuring.
[change] Some physical constants
Here are some important physical constants.
Quantity | Symbol | Value | Relative Standard Uncertainty |
---|---|---|---|
speed of light | 299 792 458 m·s−1 | defined | |
constant of gravity | 6.67428(67) × 10−11m³·kg−1·s−2 | 1.0 × 10−4 | |
Planck's constant | 6.626 068 96(33) × 10−34 J·s | 5.0 × 10−8 | |
smallest electrical charge | 1.602 176 487(40) × 10−19 C | 2.5 × 10−8 | |
electron mass | 9.109 382 15(45) × 10−31 kg | 5.0 × 10−8 |