Fermi at Trinity

TL;DR

This paper reconstructs how Enrico Fermi estimated the Trinity nuclear test yield using simple observations, providing insight into his methodology and the relationship between his estimates and radiochemical measurements.

Contribution

It offers a detailed analysis of Fermi's estimation method, which was previously undocumented, bridging observational techniques with nuclear yield calculations.

Findings

Fermi used paper pieces to estimate blast effects.

His estimate was about 40% of the radiochemically derived yield.

The paper clarifies the connection between Fermi's observations and nuclear yield estimation.

Abstract

Enrico Fermi estimated the yield of the Trinity test to be about 10 kilotons by dropping small pieces of paper and observing their motion in the blast wave. This is about 40% of the radiochemically derived value of $25 \pm 2$ kilotons that necessarily includes thermal and nuclear radiation that do not contribute to the blast. Although this story is classic, there appears to be no account of how he related his observation to the yield. This note attempts to reconstruct how he might have done so.