Planck length
| Planck length | |
|---|---|
| Unit system | Planck units |
| Unit of | length |
| Symbol | ℓP |
| 1 ℓP in ... | ... is equal to ... |
| SI units | 1.616229(38)×10−35 m |
| natural units |
11.706 ℓS 3.0542×10−25 a0 |
| imperial/US units | 6.3631×10−34 in |
In physics, the Planck length, denoted ℓP, is a unit of length, equal to 1.616229(38)×10−35 metres. It is a base unit in the system of Planck units, developed by physicist Max Planck. The Planck length can be defined from three fundamental physical constants: the speed of light in a vacuum, the Planck constant, and the gravitational constant.
The Planck length ℓP is defined as
where is the speed of light in a vacuum, G is the gravitational constant, and ħ is the reduced Planck constant. The two digits enclosed by parentheses are the estimated standard error associated with the reported numerical value.
The Planck length is about 10−20 times the diameter of a proton.
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