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To convert Bohr radii to meters: multiply by 5.29177210903 × 10⁻¹¹.
a₀ = ℏ/(mec α) = 4πε₀ℏ²/(mee²) ≈ 5.29177 × 10⁻¹¹ m, where α is the fine-structure constant.
For example, 1 Bohr Radius (a₀) = 8.296736e-18 Earth's Equatorial Radius (R⊕ (eq)).
| Bohr Radius (a₀) | Earth's Equatorial Radius (R⊕ (eq)) |
|---|---|
| 0.1 | 8.296736e-19 |
| 0.5 | 4.148368e-18 |
| 1 | 8.296736e-18 |
| 2 | 1.659347e-17 |
| 5 | 4.148368e-17 |
| 10 | 8.296736e-17 |
| 25 | 2.074184e-16 |
| 50 | 4.148368e-16 |
| 100 | 8.296736e-16 |
| 500 | 4.148368e-15 |
| 1000 | 8.296736e-15 |
The Bohr radius is the most probable distance between the nucleus and the electron in a ground-state hydrogen atom, approximately 5.292 × 10⁻¹¹ meters.
a₀ = ℏ/(mec α) = 4πε₀ℏ²/(mee²) ≈ 5.29177 × 10⁻¹¹ m, where α is the fine-structure constant.
To convert Bohr radii to meters: multiply by 5.29177210903 × 10⁻¹¹.
Sets the characteristic scale for atomic sizes. Most atoms have radii of 1–3 Bohr radii.
The Bohr radius gives atoms their characteristic size of ~1 Å (10⁻¹⁰ m), explaining why matter has the volume it does.
Confusing Bohr radius with atomic radius — the Bohr radius is specific to hydrogen; other atoms have different sizes.
The Bohr radius tells you 'how big atoms are' — about 0.5 angstroms. It's the atomic analog of a ruler for atomic-scale physics.
The Earth's equatorial radius is the distance from Earth's center to the equator, approximately 6,378.137 km.
R⊕(eq) = 6,378,137 m = 6,378.137 km. Earth's oblateness = (R_eq − R_pol)/R_eq ≈ 1/298.257.
To convert Earth radii to meters: multiply by 6,378,137.
GPS calculations, satellite orbit determination, map projections, and geophysical modeling.
Earth is not a perfect sphere — the equatorial radius is about 21 km (0.3%) larger than the polar radius due to rotational flattening.
Using the equatorial radius as if Earth were a sphere — for precision, you must account for the oblate spheroid shape.
Earth's equatorial radius (6,378 km) vs. polar radius (6,357 km) shows the planet bulges at the equator due to spinning.



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