What is a unit in physics?

[Flying Penguin]

Could someone give me a layman's definition of this unit? I've looked about on wikipedia and Google search results, but I'm still not clear on what this measurement actually is?

 

[simon009988]

planck length = sqrt[(G*h-bar)/c^3]=10^-35m
G=gravtational constant
h-bar=plancks constant over 2pi
c= speed of light
Plancks length combines all the constants of nature and gives kind of a length where quantum mechanics and general relativity breaks down. it's also the hypothetical length of an average string in string theory

 

[simon009988]

you can also combine the constants of nature to give you Planck energy and Planck time

 

[Tom D]

it is the scale at which all the forces of nature are unified