Flexi Says: The Planck length, 1.6 x 10-35 m, essentially defines a minimum size limit where known physics breaks down. The size of this unit is difficult to understand because it is so infinitesimally small. For comparison, the proton is about 100 million trillion times larger than the Planck length! At this scale, some physics predicts that all of the four fundamental forces would be indistinguishable and basically combined into a single force. Beyond this limit, scientists do not know what physics, if any, would apply. Under currently known quantum physics, it would also be impossible to measure the location, size, or any other quantitative properties of anything that might exist at this scale.