PLANCK LENGTH

The Planck length is the scale at which classical ideas about gravity and space-time cease to be valid, and quantum effects dominate. This is the 'quantum of length', the smallest measurement of length with any meaning. Quarks and leptons, the building blocks of matter, are staggeringly small. Even the largest quarks are only about an attometer( a billionth of a billionth of a meter) in diameter. But zoom in closer- a billion times more- past zeptometers and yoctometers to where the units run out of names. Then keep going a hundred million times smaller still, and you finally hit bottom. This is the Planck length, approximately 1.6×10-35 meters, believed by physicists to be the shortest possible length in the universe. Beyond this point, they say, the very notion of distance becomes meaningless. How small are we talking? It would take more Planck lengths to span a grain of sand than it would take grains of sand to span the observable universe. Compare the Planck length to the size of an atom which is already 100,000 times smaller than anything you can see with your unaided eye. Suppose that you measured the diameter of an atom in Planck lengths, and that you counted off one Planck length per second. To measure the atomic diameter in Planck lengths would take you 10,000,000 times the current age of the universe.