The hydrogen atom across eleven orders of magnitude A single logarithmic radius axis from one femtometre to about one hundred micrometres, marking four operational tiers: the nuclear core near 1 fm, the electron interior near 150 fm, the Bohr radius at 0.529 angstrom, and the coherence envelope near 110 micrometres. A bracket shows that the Bohr radius sits in the lower third of the range between the electron interior and the coherence envelope. One atom, eleven orders of magnitude Four operational tiers on a single logarithmic radius axis — nuclear core to a coherence envelope the width of a human hair. radius 1 fm 1 pm 1 Å 1 nm 1 µm 100 µm Nuclear core ~1 fm · point-like Coulomb center Electron interior reff ≈ 150 fm · the Compton engine Bohr radius a0 = 0.529 Å · the orbital raceway Coherence envelope ξ ≈ 110 µm · the pilot-wave dress lower third a0 at 29% of the reff → ξ span coherence reaches ~200,000 × a0 beyond it The enormous span — not its even division — is why the electron is a quantum object: its pilot wave fills the whole range.