text: what is planck's length?how is it the shortest possible distance covered? http://www.physlink.com/education/askexperts/ae598.cfm . check this out! planck's length is about 1 x 10^-34 m it comes from the uncertainty principle.   it is not possible to know the position and momentum of a particle at the same time with certainty.   change in position times change in momentum equals planks constant divided by four pi.