The Planck length is so small that our current laws of physics may no longer tell the whole story.
At 1.616 × 10⁻³⁵ metres, it marks the scale where quantum effects of gravity are expected to become important. It is about 20 orders of magnitude smaller than a proton.
Einstein’s general relativity describes gravity on cosmic scales, while quantum mechanics governs the microscopic world. At the Planck scale, these two frameworks are expected to meet, but we still lack a complete theory that unites them.
