Planck Length

In general relativity, two constants: the speed of light c and Newton's gravitational constant G, appear throughout. According to Einstein's general relativity relates to Newton's theory of gravity, and concludes that nothing travels faster than light. In quantum field theory, c is paired with Planck's constant h.

Planck derived ways to use these three constants to define the units of mass, length and time.

Planck length can be formed from the constants c, h and G; significant lengths in quantum gravity become small multiples of the Planck length, according to the dimensional analysis. In certain quantum gravity theories, space-time structure becomes dominated by quantum effects at the length scale, creating a foamy structure. For extra large dimensions, the strength of gravity measurement can be less than its small-scale value. In such a condition, there would be no physical significance of Planck length, and quantum gravitational effects have larger values.

The Planck length LP takes the constants of nature and by combining their units form a length. Planck's constant, h, has units of Joule seconds, gravitation constant-G has units of N.m²kg^-2, and the speed of light c has units of ms^-1. By combining these constants, Planck length can be derived using the formula:

`L_(p) = sqrt((Gh)/(2 pi c3))`

In the Planck length, the unit of length - L_p, = 1.616252(81) ×10−35 m or 10-20 times the proton size.   

Planck scale       

The unit of length - Planck length is extremely small, in meters. To understand this scale in physics, quantum gravity plays an important role. To calculate a length using these constants, Planck length can be multiplied by a numerical factor 2Π.