 Cross section (physics)

The neutron temperature example is crucial: you just can't give the cross section of a target alone, the energy of the incoming beam also matters.

In physics, the term "cross section" refers to a measure of the probability of an interaction between particles, typically in the context of scattering experiments or nuclear reactions. It is a crucial concept in fields such as high-energy particle physics, nuclear physics, and astrophysics. The concept of cross section can be understood as follows: 1. **Geometric Analogy**: Imagine a beam of particles (like protons or neutrons) being directed at a target (another particle or a nucleus).