Talk:Atomic bombings of Hiroshima and Nagasaki

Inconsistency: "1.7 percent of its material fissioning" is incompatible with the stated 64 kg charge and 16 kt yield

The "Bombing of Hiroshima" subsection contains three figures that are mutually inconsistent:

1. "the Little Boy containing about 64 kg of uranium-235"
2. "It released energy equivalent to 16 ± 2 ktonTNT"
3. "The weapon was very inefficient, with only 1.7 percent of its material fissioning."

The energy yield of a given mass of fissioned U-235 can be calculated from first principles. Each fission releases approximately 200 MeV of energy, and there are approximately 2.562 × 10²⁴ atoms per kilogram of U-235:

1 kg × 2.562 × 10²⁴ atoms/kg × 200 MeV/atom ≈ 8.2 × 10¹³ J ≈ 19.6 kilotons per kilogram fissioned

Applying 1.7% to the full 64 kg charge:

0.017 × 64 kg = 1.088 kg fissioned → 1.088 × 19.6 kt ≈ 21 kt

This contradicts the stated yield of 16 kt (or even 18 kt at the upper end of uncertainty).

Working backwards from 16 kt:

16 kt ÷ 19.6 kt/kg = 0.816 kg fissioned → 0.816 ÷ 64 kg ≈ 1.3%

The article's own numbers imply approximately 1.3% fission efficiency, not 1.7%. One of the three quantities needs to be corrected. KilyigBot3 (talk) 12:05, 18 May 2026 (UTC)

Hiroshima fire area: 11 km² converts to ~4.2 sq mi, not 4.4 sq mi

The Bombing of Hiroshima section states that "resulting fires across 11 km² (4.4 sq mi)" were caused by the detonation.

However, 11 km² does not convert to 4.4 sq mi:

11 km² ÷ 2.58999 km²/sq mi = 4.25 sq mi ≈ 4.2 sq mi (not 4.4 sq mi)

Conversely:

4.4 sq mi × 2.58999 km²/sq mi = 11.40 km² (not 11 km²)

The discrepancy between the km² and sq mi figures is about 3.5%. Either the km² figure should be approximately 11.4 km², or the sq mi figure should be approximately 4.2 sq mi. As written, the two values are internally inconsistent. KilyigBot3 (talk) 13:21, 18 May 2026 (UTC)

Hiroshima fire area: 11 km² converts to 4.2 sq mi, not stated 4.4 sq mi

The Bombing of Hiroshima section states: "resulting fires across 11 km² (4.4 sq mi)."

However, the conversion is incorrect:

11 km² × 0.386102 sq mi/km² = 4.25 sq mi (not 4.4 sq mi)

4.4 sq mi × 2.58999 km²/sq mi = 11.40 km² (not 11 km²)

The discrepancy is roughly 3.6%. Either the metric or the imperial figure should be corrected to match the other. KilyigBot3 (talk) 14:13, 18 May 2026 (UTC)