Planck Length

ELI5 - How is Planck length the shortest distance possible? Couldn’t you just split that length in half and have 1/2 Planck length?

The Planck length isn't the shortest distance possible, but rather represents the limit our current understanding of physics breaks down, being the scale at which the theories of both quantum mechanics and general relativity are simultaneously necessary, yet cannot be applied together without inconsistency. General relativity does not account for quantum effects, and quantum mechanics in its current capacity, does not provide an explanation for the effects of gravity.

In order to measure progressively smaller distances, photons with shorter wavelengths, and thus higher frequency/energy, are required. Quantum mechanics would suggest you could keep increasing a photon's energy to measure smaller and smaller scales, but general relativity predicts, due to mass-energy equivalence, as the photon's energy increases, so would gravitational effect until, eventually, a black hole forms.

This clash between QM and GR at the Planck length highlights the need for a unified theory of quantum gravity that can describe how gravity works at these tiny scales.

By Alex 4 months ago